Webinar with SPAB Scholars 2022 Programme on Building Repairs and Materials

00:00:00:00 - 00:00:30:24

Speaker 1

Niki Lauder She's our Conservation Accredited Historic Buildings Advisor at Historic England, and she is introducing the SPAB 2022 scholars, which are Sinead Scullion and Katie Hood, Jacob Long, Serena Gildea and their various case studies in approach to repairs for cost on reinforced concrete and masonry, and Catherine Bull, who is with us today. Before we move on, there are a couple of links for the take the conservation of guidance research, which I will be popping into the chat in a second.

00:00:31:08 - 00:00:39:17

Speaker 1

But before that I'm now going to hand over to edit to Catherine just to make sure that I can see her. Catherine And I'm going to pass over to you.

00:00:40:10 - 00:01:11:07

Speaker 2

Hello. Thank you very much. And hello everyone, and thank you, Alice. As I said, my name is Catherine Bull and I'm a building surveyor and was a scholar in the year 2000, And since then I've worked in various conservation roles a client, project manager, contractor and before joining the SPAB in 2016 to run the scholarship program, I work alongside Pip Sodeen, who runs Fellowship Program for skilled crafts people.

00:01:12:13 - 00:02:08:00

Speaker 2

I'm going to give you a short introduction to the scholarship program and then we'll be handing over to the 2022 scholars who, as I said with Sinead Scullion, who was working in Dublin before taking up the scholarship place and now works in the trust office of Donald Associates. Katie Hood, structural Engineer, working at Narrow Associates in Edinburgh. Jacob Long, an architectural assistant child system architects in Bristol, and Serena Gildea, the structural engineer working in IID Design ID in Belfast so SPAB is the oldest conservation charity in the country and guides people in the repair and maintaining and adapting old buildings.

00:02:08:08 - 00:02:34:24

Speaker 2

The first scholarship was awarded back in 1930 in recognition of the need for architects to see works on site to understand the approach required for the successful repair of historic buildings and the best methods to employ without such experience. It's only after experimenting on buildings that people come to learn how valuable these structures are and the care and treatment that they need it.

00:02:35:07 - 00:03:15:17

Speaker 2

And this actually remains core to the scholarship program. We choose three or four scholars each year selected by interview process. They travel around together for nine months, entering a whirlwind of live visiting live projects around the country hosted by clients, practitioners, contractors, craftspeople, suppliers. So immersing themselves in the care repair of historic buildings for those six months. Often those visits are shared with fellows, which they find greatly beneficial.

00:03:15:17 - 00:03:47:08

Speaker 2

They hear questions craftspeople ask different questions to the questions that scholars ask, and they benefit greatly from learning from each other. The final three months are then spent studying arts and culture at the Country House. They'll spend the week at several country houses and this is designed to develop scholars, sensitivities and tastes in the hope that it sort of adds another element and informs a more sensitive approach when they come to the conservation practice, practitioners.

00:03:47:12 - 00:04:43:05

Speaker 2

[...] and probably bring some skills that are relevant to whether they're looking after a cathedral or country church or caring for country houses of vernacular cottages. The aim of the program is to bridge the gap between academic study and onsite work, giving them and giving them a thorough understanding of the SPAB philosophy. Honest repair rather than replacement as set out in the purpose of the SPAB [...] The bridging of the gap between professional studies and practical site studies is very important, and it brings also helps bring the idea of developing the design of design and repair closer together and recognizing the skills of the work that the people are doing and what they can and cannot be achieved

00:04:43:05 - 00:05:24:03

Speaker 2

on site. And this is done by them working alongside, getting practical experience on site under expert tuition. It's amazing what difference can be when you actually see someone doing something. Many of you will know. You suddenly realize what can and can't be achieved. And this is a very important learning aspect of the scholarship. And we also want them to be understanding the importance of the natural materials, the quality of craft skills relating to buildings, and then to the landscape, and avoiding a loss of styles and associated.

00:05:24:12 - 00:05:33:09

Speaker 2

Sorry, I just lost my place there of new work. I'm going to ask you a question here. Please.

00:05:36:24 - 00:05:39:00

Speaker 2

So as we go. Lovely. Thank you.

00:05:39:01 - 00:05:44:09

Speaker 1

Sorry, Catherine, I'm trying to do two things at once in my multitasking. It's not happening. Apologies, everyone. So there you go.

00:05:45:03 - 00:05:50:13

Speaker 2

The rest is, can we do two questions now at this time? Perhaps do that? Just one.

00:05:50:21 - 00:05:55:03

Speaker 1

Just give everybody a chance for this one and I will open the next one if you bear with me.

00:05:55:23 - 00:05:58:08

Speaker 2

Thank you.

00:06:01:04 - 00:06:05:06

Speaker 1

And there's another one just popping into the screen.

00:06:08:08 - 00:06:11:14

Speaker 1

Great, Thank you, everybody.

00:06:15:04 - 00:06:27:06

Speaker 1

Right, Catherine. I'm just going to broadcast the results, even though it's almost even stretch It's quite nice. And back to you, Catherine.

00:06:28:05 - 00:06:52:05

Speaker 2

Thank you Alice. So what the SPAB approach that we're trying to bring to scholars is the one of timely repair, we often think boring old maintenance, but obviously this is crucial and very important to the to the SPAB that we sort of regular work is undertaken.

00:06:54:06 - 00:07:29:07

Speaker 2

The importance of skilled craft in repair, essential in all aspects, both in replacement repair and in new work. And then when we make honest interventions, so not trying to fool those that come after, if they have any repairs or of an old repair, then they all and they meet skilled craft practitioners and craftspeople and Alice, If I can ask you the final question.

00:07:29:22 - 00:07:30:23

Speaker 2

So there's a.

00:07:39:08 - 00:07:55:07

Speaker 1

We have a lot of. Yes, it's excellent. It's good to see actually. Great. Give a little second. Perfect. So I think the resounding yes there, Catherine. In answer to your question.

00:07:55:07 - 00:08:26:00

Speaker 2

That's very good. And thank you. Thank you very much. So one of the things that SPAB and we're very much working on, a Pip Sodeen and with other colleagues is the reason for that question is obviously very keen on increasing the diversity and of underrepresented groups. And if anyone has interest to them, thinks that yes, maybe, maybe a collaborative approach to work with then, please do get in touch with us if we find us to speak to you.

00:08:26:07 - 00:08:57:03

Speaker 2

And then in terms of looking ahead with the scholarship picture here, Jacopo, looking ahead at this point, but is very much so now is actually the applications for 2024 will be closing on the 24th of October. Interviews will be held in December at the start of where we have an informal gathering here to hear from previous scholars. And the program will beginning in March 2024.

00:08:57:03 - 00:09:10:08

Speaker 2

And for anyone who's got any questions, please do get in touch. Very happy to chat to people. And also former scholars are always willing to talk to people. And now I'd like to pass over to Sinead.

00:09:13:24 - 00:09:39:21

Speaker 2

Lots of things happening. Thanks, Catherine. So our talk today is going to be at the variety of repairs that we saw on the scholarship. So on the scholarship, we realized when talking to people about a SPAB repair, they generally conjure the idea of a tile repair almost immediately. So as you can see in this photo from the 1920s, we have a slab worker who is putting in the tile repair at rotting Dean Church in Sussex.

00:09:40:06 - 00:09:49:23

Speaker 2

However, in practice there are many ways to achieve a technically and philosophically appropriate repair, and this presentation is going to talk through a range of approaches that we saw on the program.

00:09:54:09 - 00:10:46:22

Speaker 2

So firstly, when we approach our projects, we need to decide the level of intervention we will undertake ranging from no intervention, preservation, conservation, restoration or demolish and build a new from this list the SPAB would advocate for preservation so halting decay or change, or keeping the existing fabric as found or conservation. So guiding continuing change for the longevity of the existing fabric or new elements might be introduced to manage deterioration and allow active re-use of the existing structure, whereas the SPAB would typically be opposed to the idea of no intervention, restoration or demolition and the SPAB take a strong stance on repair of a restoration in their founding manifesto in 1877.

00:10:46:22 - 00:11:12:01

Speaker 2

They note that we should show no pretense of other art and resist all tampering with either fabric or ornament of the building. As it stands, that idea of minimum intervention and jumping forward we now have the SPAB approach, which is a modern or term interpretation of the manifesto and expands on the ideas laid out in the manifesto for a modern audience.

00:11:12:09 - 00:11:33:18

Speaker 2

And in this document we have the idea of a conservative repair, which is outlined as follows And similar to the manifesto, it notes that we must retain as much as possible of the fabric of the building's existing fabric and where repair is required. It might be done to match the existing materials of our building or sometimes use of compatible alternatives.

00:11:34:06 - 00:12:04:00

Speaker 2

And ultimately, though, it should be done with thorough investigation and understanding of the whole building before we decide what needs to be carried out. Since Mobile and given that there are many ways to approach a repair, it is important to understand our biases and how they might influence on selecting a technically inappropriate consent conservative repair. So, for example, are you a structural engineer, historian, architect, stonemason, or even an accountant?

00:12:04:09 - 00:12:31:23

Speaker 2

And as an architect, it's important to be aware that you might be and have a bias for the aesthetic of a repair, but this shouldn't have a negative impact on its technical performance. So, for example, if you're repointing a wall and it was, it is typically best practice to bring the mortar joints flush with the face of the existing the adjacent fabric to not create water ledges.

00:12:32:22 - 00:13:00:06

Speaker 2

And ultimately decision should be multi-disciplinary and focus on prolonging the longevity of existing fabric for future generations, which is a key philosophy of SPAB. Decisions, should also be based on the context. It was quite evident as we traveled around that there's no one approach to all repairs and both physical fabric and human side need to be considered in how we approach repairs.

00:13:00:06 - 00:13:30:03

Speaker 2

So moving on to some photographs, and I just want to say as well that these are not to show best are bad practice. They're just to provide some quick examples of what we saw. So starting with Castle Acre Priory in Norfolk, we see masonry infill undertaken presumably by three different craftspeople, and this can show how much we get a variation using a similar material palette where personal biases influence the results.

00:13:30:03 - 00:13:55:22

Speaker 2

And this slide is to show some examples of legibility of repairs. So starting with the line plaster repair, we have a like for like where the historic layers of paint are retained. The existing in the middle, we have a stained glass repair where existing decorative glazing is suspended in plain glazing. And then the third images of a Georgian brickwork repair that is more difficult to read, but the new brick and mortar is compatible with existing and minimal.

00:13:55:22 - 00:14:26:13

Speaker 2

The material is removed in this process, making it technically appropriate for its surrounding here and IT range of some timber repairs that we saw. So in the middle we have a red steel supporting existing timber, which is quite an honest repair. And this is an example of doing as little as needed, as much as necessary. So minimal intervention and the two images on the other side then show how we can have a new like for like material inserted.

00:14:26:13 - 00:14:56:19

Speaker 2

And this might be less legible, but it can be so be read by those familiar with timber, especially as no pagination is applied to make the finish match end with the existing around it. Moving on to an example of compatible alternative repair on a larger scale, we have this case study of Orford Castle, where you can see the existing stepped area stone in the wall is crumbling quite badly and posing quite an issue to the building.

00:14:57:08 - 00:15:29:21

Speaker 2

And here it was decided to introduce a new hot lime harl to the full external facade acting to repair and protect the existing external walls. So this is an example of a larger scale intervention and putting in a new material that's compatible with the existing coming back to the point of repair, longevity and performance, I'm sure we've all seen examples of mortar repairs that have not been sacrificial against the existing fabric and the damage that this can cause.

00:15:30:14 - 00:16:01:13

Speaker 2

Similarly, we also need to consider how sacrificial this repair is. For example, looking at the picture of the church wall and with the flint makes distinct that fabric and new brick infill, we can see that this brick is quite soft and even though it is sacrificial against the existing fabric and we need to know how long we want the repair to last and what lifespan is needed for the project.

00:16:01:13 - 00:16:27:08

Speaker 2

So for this talk, we're looking at three case studies. As you can see, the map on the right hand side shows the all the projects I visited on this scholarship and from this we've taken and Glasgow School of Art. Okay, a cast iron that'll be discussed by Katie. We have gallery in Fairy Gala Fairydean Football Club, which will be discussed by Serena and masonary repairs at your castle, which we discussed by Jacob.

00:16:27:08 - 00:16:34:21

Speaker 2

So handing over to Katie now.

00:16:34:21 - 00:17:00:23

Speaker 3

Thanks Sinead and hopefully you can all hear me. So doing a bit more of a deep dive into one specific material and its repair. So one of the projects that we were lucky enough to visit on the scholarship, well, I'd been lucky enough to to work on slightly before we did, but being on the scholarship gave me a chance to think about it from a really different perspective and to start delving into information that I hadn't had the chance to investigate before.

00:17:00:23 - 00:17:28:09

Speaker 3

So many of you may be familiar with the Glasgow School of Arts Mackintosh Building. It's thought of as Charles Rennie Mackintosh’s masterwork and is considered important in the story of the arts and crafts movement and the arts and nouveau movement, particularly in Scotland. As such, it's been Grade A Listed since 1966. Mackintosh is often considered an architect of interiors, and here you can see his beautiful library at the School of Art.

00:17:29:01 - 00:17:54:21

Speaker 3

But in this, the School of Art. One of the first purpose built schools of art and design in the UK. He really showcased his understanding of creating incredible spaces. Now it's a really big building, essentially takes up about 50% of a city block, and it was built into in two different phases and with the difficulties of funding such an ambitious project and they'll come back to these phases.

00:17:54:21 - 00:18:27:21

Speaker 3

But the first was completed in 1897 and the second was in 1909. Although sometimes said to be unappreciated for his architectural design during his lifetime, Mackintosh's art school became iconic in the minds of young architects and designers in Scotland, and very important to the cultural life of Glasgow and to the hearts and minds of Glaswegians. Unfortunately, it caught fire and in 2014 the fire caused damage to about 10% of the structure of the school.

00:18:29:01 - 00:18:55:20

Speaker 3

It was very carefully prepared and took two years for restoration to get underway and it was all going well in 2018 when it caught fire again and we lost about 90% of the building's structure at this point. Now, this is when this is where the building was at when I first got to know it. But by the time we visited as part of the scholarship, the remaining structure had been stabilized and the debris cleared from the interiors.

00:18:55:20 - 00:19:20:06

Speaker 3

We were able to visit what was left of those iconic spaces that Mackintosh had created. The future of the building is a little up in the air. Although the art school has pledged to repair it. It is unclear what this will mean at the moment. But even without knowing that knowing exactly what the future holds for this building, it's a fascinating place to visit as a conservation structural engineer like myself or an architect who is interested in structural history.

00:19:20:18 - 00:19:42:00

Speaker 3

Its structure has been laid bare, and this image brings me to what I wanted to focus on, which is historic, structural metalwork and what I was able to learn about it. While reading around the topic on the scholarship repair and preservation of architecture. Architectural metalwork is quite a common theme in conservation discussions when we're talking about railings or gates or finials.

00:19:42:12 - 00:20:06:15

Speaker 3

And although there are quite a few excellent reference texts on the subject of the structural elements, there's sometimes less often considered. So here we go with an incredibly potted history of metal structural elements. FERROUS They're in the in brackets. And all I've got time to say about that is it means that I'm talking about things to do with iron.

00:20:07:05 - 00:20:39:24

Speaker 3

Now, iron and building has buildings as a two and a half millennia long history, which I will cover quite sacrilegious in less than a minute. So please forgive me if we start we start in 500 B.C. and we were already extracting iron from rocks by heating them up to 700 degrees. Now this produces sort of puffy blooms of iron which can then be smashed together, and they form the first forms of wrought iron, which is this process of smashing those bits together to create a full form.

00:20:40:06 - 00:21:05:01

Speaker 3

And it took until the 13th century for us to work out ways to smash enough of these blooms together to create the first full structural beams of wrought iron. And we didn't get much further than that until the Industrial Revolution. And in the 18th century, we invented furnaces which let us melt these lumps of iron over a thousand degrees and put them into molds, which gave us cast iron structural elements.

00:21:05:15 - 00:21:31:03

Speaker 3

They would take until the 19th century for us to really get to grips with what the chemical differences were between these two forms of iron and to learn how to control the composition of the melted mixture, to optimize the final properties. And with that understanding, we were able to create steel by the early 20th century steel rules of Now this is a much more thoroughly researched graphic that I think from one of those excellent publications I mentioned.

00:21:31:17 - 00:21:54:14

Speaker 3

And here you can see why, you can see how we can chart the final steps of that evolution at the end of the seven from the end of the 18th century. Now, what context connects the Mackintosh building? So interestingly with this graph is those two phases of construction that I mentioned at the start. They land right where this transition to steel as the main structural element is taking place.

00:21:55:06 - 00:22:30:05

Speaker 3

And in a fantastically superb, appropriate moment of serendipity, we can knows we have cast iron lintels and to the west end of the building built that little bit later over almost identical windows. We have steel lintels. It's so I wanted to take you through the material behavior differences of the different forms of iron, but I think I'm going to run out of time on that whenever I delves too deeply.

00:22:30:05 - 00:23:01:23

Speaker 3

So I'll just flash it up on the screen here. The key thing to take away from the material differences of cast iron wrought iron and steel is actually they lead to very different looking structural elements, cast iron sections in particular are always very big with complex geometries that allow the beams to act almost entirely in compression, much more, in fact, sometimes much more like an arch than a beam.

00:23:01:23 - 00:23:35:20

Speaker 3

And the key thing to know about cast iron that's been through fire is that actually it's quite good at high heat. It hardly ever warps and distorts like we would typically see with steel and like you saw in steel in that first photo when I said that the structure had been laid bare. But when we get to over 600 degrees, the thermal expansion of the different elements becomes a problem and it changes the way that those complex compression geometries in the cast iron elements interact with the structure around them and suddenly tension cracks start forming.

00:23:36:06 - 00:23:59:08

Speaker 3

Now, these failures are quite clear at the Mackintosh building. So it's a really interesting question of how can we hope to keep this interesting historic fabric in place. Now the engineers are looking after the building now, are trying various methods to do this. They were kind of a long list of options available. Whether they'll work or not is another question.

00:23:59:08 - 00:24:46:01

Speaker 3

And these two that they are trying to tackle at the moment are analysis, investigation and justifying the beam and load testing it. So they've taken one beam, as you can see here, this one, and they've removed it from the building. They have done a thorough clean. So there are visual assessment and recording. It's then been thoroughly cleaned and inspected for cracks using nondestructive techniques and knowing exactly the locations of the cracks they've been able to show with structural analysis that all of these cracks, when it goes back in the building, will actually be in compression and therefore not pose a structural issue.

00:24:46:23 - 00:25:09:13

Speaker 3

Now, this sounds like a big claim, but the logic follows through. If you understand that the way those cast iron beams were designed was to put them into compression. In a lot of cases, then this could be a way forward for reusing this structural fabric despite its deterioration and to provide an extra level of confidence. They've also allowing for load testing the beams.

00:25:09:13 - 00:25:28:23

Speaker 3

Now, it's really early days and it's unlikely to be a suitable approach for more heavily damaged beams within the building. But if the engineers are to succeed in justifying the re-use of some of these beams that we its structural colleagues are Serena Gildea.

00:25:33:03 - 00:25:59:22

Speaker 4

Thanks, Katie. And so I've decided to discuss the repair of 20th century reinforced concrete stadium that we visited back in May 2020 to the Gala Fairydean Rovers Football Club in Scotland. So the structure is striking its brutalist architecture and was under repair when we met up with Pascal or Steve Wood. And Steve works for Narrows Associates and was a structural engineer leading the project.

00:25:59:22 - 00:26:24:12

Speaker 4

And as you can see, it's now has a visible build up of moss and algae growths on the rear elevation. And if you look closely at the roof structure, you'll see some exposed portions of reinforcement bar coming through just in this third photograph. So this is first and foremost a structural concrete repair project. And but just before we get into the details of it, let me introduce you to the project.

00:26:25:02 - 00:26:45:24

Speaker 4

I would describe it as a piece of art and like the shadows and the angles, and it's just a really prominent structure. And I love the exposed concrete finish with the broad marks from the formwork and how it's somehow really elegant but crude. And I think it really strikes this interesting balance. And so it's a Grade A Listed structure.

00:26:46:09 - 00:27:15:24

Speaker 4

1965 the architects, Peter Ramsey and the engineer was (indistinct) And so the structure itself, as I said, it's reinforced concrete and that's both in situ concrete as well as there's precast elements in there as well. And if you look at the right hand photograph, you'll see the four vertical cantilever columns to that supports the rear, the supports of this and the stand and the spectator seating is constructed with the precast elements.

00:27:16:07 - 00:28:01:11

Speaker 4

That's obviously pitch side. So the structure itself is designed with these horizontal cantilever beams supporting the risk. And so they split out from the columns and this little 3D image, along with a few other photographs actually I actually received from Steve, would very kindly sent me some additional images. So this one is really helpful to understand the actual layout and but the issues with these cantilever splayed beams, the risk is that it actually creates numerous different catchment areas for rainwater and then the drainage of these areas pass through the structure in numerous different and numerous different locations passing into vertical stormwater pipes embedded within the four reinforced concrete columns.

00:28:01:22 - 00:28:34:03

Speaker 4

And so that would all be fine, except for the fact that there's a real access issue and that there the there's no access really on to the risks unless you get a cherry pictures of that up. I'll just see from this photograph that there is a really big issue with Moss growth and other other like salts and algae up there.

00:28:34:03 - 00:29:01:05

Speaker 4

And so the other factor then as well, that is an issue for this. The risk is that it's during the actual construction of a reinforced concrete building, the actual cover is really important and there's a real issue with making sure that you don't break that cover really. And when you're actually constructing it, people are standing obviously on the rebar and it's very difficult.

00:29:01:05 - 00:29:21:18

Speaker 4

But the cover specifies for this structure was really minimal. So the drawings that Steve told us was that it was only half an inch. So that's like 12.7 mil to be exact. So that leaves no room for error on site. And that seems to be are some of the issues with cover and not being mentioned. And it is a common issue.

00:29:22:18 - 00:29:56:19

Speaker 4

So one of the other the standard seating that in particular the precast elements which can be seen in the photograph and second photograph and there were some clear issues with corrosion of reinforcement bars and minimal cover. Again, and one other significant issue with the precast elements was the fact that the void below the stand was actually an extract point for the changing rooms and showers below, which created this really damp, humid environment, which didn't help us see the obviously the corrosion issues and and the shallow cover.

00:29:57:15 - 00:30:22:24

Speaker 4

So just on to the repair. And so so there was a mix of approaches used depending on the elements in question whether and whether it could be seen, whether it was functional, a cover was available in the specific areas and firstly but, but first, like visual surveys were carried out to identify areas of concern and then testing of the concrete across various elements.

00:30:22:24 - 00:30:43:18

Speaker 4

So you'd be testing for the like. All right. And then completing of a photographic analysis of the concrete. And so the repair for the roofs roof was cleaned and it was patched, repaired and the drainage pipes were all cleaned out and then a membrane was applied, a waterproof membrane to the risk structure. And then where there were large portions of concrete that could be broken out.

00:30:43:18 - 00:31:20:12

Speaker 4

This allowed for liquid natural concrete mix to be placed, which you can see which was happening in this in the left hand photograph. And so they're actually creating a better concrete mix to repair that, but they also use false render where required and, and on the external facade, one of the interesting things was the fact that they created formwork molds of the existing finish so that the new formwork would be lying then with the mold to recreate the fish into the recreate the finish so that the texture would be the same.

00:31:20:12 - 00:31:54:11

Speaker 4

And so and then repair of the seating and the well, the main thing before they suppose did enter this repair work, they had the main issue was resolved in that they have installed mechanical ventilation and relative humidity sensor so that if the humidity reached a certain level, mechanical ventilation turns on. And they've also changed where the extract is now for the the changing rooms, which means that it goes external and not into this void anymore, but then the repair of the actual corroding reinforcing bars were all broken out, which you have to do when you're a parent.

00:31:54:11 - 00:32:24:24

Speaker 4

Copy structures like this. So you have to break out the entire section. You can see in the right hand photograph where you create a full, you want to actually get access to the full bar so that you can clean it and protect it and then place the concrete again around it. So and then just the item and some finished photographs that I got through from Steve actually, actually some repairs to the underside of the rest of the city and sitting on the left hand side and then a finished picture of the cleaned and paste repaired structure, which I think looks great and nice.

00:32:25:00 - 00:32:43:13

Speaker 4

They, they reinstated the glass balustrade and the stadium is open and they're in discussions in place about a third phase of work to protect the structure further. But an interesting note that these actually point out to me was that if you see on the second bay, you'll see there's kind of like a wave tide mark on the bottom of the structure.

00:32:43:22 - 00:33:07:24

Speaker 4

And that photograph that we have, Mark, is actually in some of the original photographs just after it was opened. So it kind of shows that there was some top touch ups required to the finish at the time of construction. And then just finally to finalize the discussion around the repair of reinforced concrete. This is first and foremost a structural concrete repair project and this leads the repair solution.

00:33:07:24 - 00:33:33:13

Speaker 4

But with the right engineer and their understanding of conservative repair, the esthetic finish for the Grade A-Listed building was also at the forefront of their mind. And so basic run through how to repair reinforced concrete buildings. Firstly, you have a visual survey with a structural engineer and a corrosion material specialist Engineer is quite important and then testing to understand what the concrete mix is, what type of corrosion you're dealing with.

00:33:33:13 - 00:33:56:19

Speaker 4

So carbonation testing, fluoride testing, resistivity testing and then your options then for the repair include things like your standard parts repair, which have been done with the structure realization, which is a process of resetting the clock back to essentially where the concrete was poured again and which helps protect it, protect the reinforcement and then anti carbonation coatings and can stop carbonation.

00:33:56:19 - 00:34:24:10

Speaker 4

And at a point if it's tested and found that not to have penetrated the full depth of the cover and then you've obviously got your electrochemical methods such as cathartic protection and but with cathartic protection, Suzanne, the realization you have to make sure that you have a competent and qualified designer because they are regulated through the international standard one five, two, five, seven and four levels of competency.

00:34:24:15 - 00:34:47:03

Speaker 4

And I again, if I've known this through my own work in relation to working along with a company called McFarlane Consulting, who we work alongside as our kind of corrosion materials specialist and who does the design for us in there of a specific levels of competency for specific structures. So it's a really useful tip to make sure that you're working with good people as you're looking at things like this.

00:34:47:19 - 00:34:57:15

Speaker 4

And that's my quick run through of repair, of reinforced concrete protected structures. And I'm going to pass you over to Jacob Long okay.

00:34:58:19 - 00:35:06:21

Speaker 5

Thanks very much. And I hope you can tell me about Duart Castle, which is on the Isle of Mull near the Hebrides, and such as the West Coast of.

00:35:07:00 - 00:35:17:21

Speaker 1

Hi, Jacob, it's Alice your Technical host I'm just going to ask you to sign out again because you've gone all crackly, so it might just refresh. No, no, no apologies. Okay, I'll give you a few seconds.

00:35:18:16 - 00:35:19:08

Speaker 5

Thanks. Bye.

00:35:19:21 - 00:35:40:19

Speaker 1

Sorry, everyone. I just think it would be better if we can hear him clearly. So we'll just wait for him to come back in and I will pop him back up. So please bear with us. Thank you. If you have any other questions for our speakers, please do pop them into the chat box at the top of the screen with the green writing is and will be able to use them at the Q&A.

00:35:41:08 - 00:35:43:04

Speaker 1

Just waiting for Jacob to come back in.

00:35:51:23 - 00:35:52:14

Speaker 2

Right.

00:35:56:03 - 00:36:17:04

Speaker 1

Now. Jacob, you should be back. And he should see a microphone. Hello, Jacob.

00:36:17:04 - 00:36:17:12

Speaker 5

Hi.

00:36:18:03 - 00:36:21:23

Speaker 1

Oh, yes, that's so much better. Thank you. And I think posterity should.

00:36:21:23 - 00:37:01:04

Speaker 5

Just just stop working. Turned off. Okay, So. So again. So I want to talk about Duart Castle on the Isle of Mull. So off the west coast of Scotland in Aberdeen. And it's a fascinating example of a project which were an extreme example of building where this is a dam problem and it's had a dam problem for 100 years, really partly as a result of past use of inappropriate materials, previous repairs carried out without a full understanding of the root cause of the problem, and then said ongoing, I guess minor but fairly widespread sort of deterioration of water, sitting details, roofing, etc..

00:37:01:04 - 00:37:23:05

Speaker 5

So lack of maintenance really, and it's exacerbated by the by the climate and so on. The Met Office weather map on the far right, you can see that it's just off the West Coast of Scotland, there is about three and a half meters of rain a year. So that coupled with the location of the castle off off the coast of Mull, basically.

00:37:23:05 - 00:37:47:07

Speaker 5

So Scotland's next page just quickly to give an overview of the history. So that's records of the castle from the 14th century as a stronghold of a clan McClean. And I think that the key was likely to have been built maybe a hundred years prior in the previous century from Basalts. And Whin Stone Blocks, which are very hot, very dense, very impervious to moisture.

00:37:48:12 - 00:38:19:16

Speaker 5

So the castle changed hands various times over the years, basically, depending on which cloud was most dominant, the you captured it. So the sketch on the left shows the castle just before it was abandoned in the 18th century in 1748 the date on it had just been taken over by the Earl of Argyll. And then the next hundred and 50 years, it was just left as soon as it ruined really did degrade the so these joins on the right so the state it was in the beginning of the 20th century.

00:38:19:16 - 00:39:04:13

Speaker 5

So 1981 just before it was taken over back by the Maclean family. And I think that plan just sort of shows the thickness of the masonry. I think that's ten foot, but the people's kind of according to the scale. So, yeah. Lachlan Maclean top left this croft He bought the castle in 1910. It came back into the hands of Maclean and he employed Sir John Burnet and son for Scotland Neath to convert the castle back into a sort of habitable building, and that the left and right photographs of the before and after an amazing kind of transformation.

00:39:04:13 - 00:39:25:10

Speaker 5

And interestingly, after the point at which time the classic School of art had been both so interesting this in sketches at his talk and then an image below. Below is the first coffin was taken out of MIT midway through the construction process. You can see the just how voided for the masonry was prior to sort of being rebuilt.

00:39:25:10 - 00:39:54:14

Speaker 5

Flush these really big blocks of stone with, I guess, slate in the stone pinning between them to reduce the kind of mortarboard that was built up flush so that the sort of problems that they'd been having through the 20th century really it's just one of moisture ingress. The various repair projects that happened in the seventies in the nineties to try and establish the ingress of moisture.

00:39:54:14 - 00:40:39:21

Speaker 5

And I think it really works and it got supported 2012 where the family was sort of living that it was so that they were seriously contemplating moving out. I think in winter 2013 to 14 they'd lost four ceilings. It just looked really, really bad and points at that point in time. Martin Hadlington Conservation Officer A.V. is a material scientist, building pathologist to, I guess to start looking into it, to start doing some analysis into issues to try and sort of understand the fundamentals behind the problem and I guess I was really, really keen to sort of success.

00:40:39:22 - 00:41:05:04

Speaker 5

The project really is just that at the beginning they employed a sort of number of techniques. That's what research on site inspections and materials testing to build, kind of taking the lead on all three of those with the Phase one masonry contractor and Boston just to try and understand kind of what was going on with with the with the masonry, with the with the fabric.

00:41:05:20 - 00:41:27:06

Speaker 5

And we spent some time out at those lab in Stirling just to better understand the techniques that you can employ when you're trying to get to the bottom of a problem substrate. Looking through a microscope. It's a plaster, I think so, yeah. It's just a really strong foundation on the tube for the, for informing the repairs so that we visited in September last year.

00:41:28:07 - 00:41:53:20

Speaker 5

We actually been on site for ten years working. It really controls considered pace quite amazing to kind of have an opportunity to work and work in that way. We say would ultimately you see that Mason and his team for a week and and most of them visited for a day. So we had a day with little for effort to speak to all of them about their perspective on the project and find out their thoughts on it, really.

00:41:55:00 - 00:42:21:15

Speaker 5

And at the point in time we with dates drop the scaffold to the south elevation would finish that they'd finished the masonry post, the the keep courtyard elevation and it completed quite extensive roof works that reflected some rough patches that work in asphalt and some of the flat roof sections. And it just commenced. So you can see in that photograph the scuffle just commenced work to the north elevation.

00:42:22:18 - 00:42:49:23

Speaker 5

So we got a chance to have that on. So just to sort of delve into one of the technical issues that they may be ready for coming in for left in. As you can see, it's really, really hot, dense, impervious cementitious pointing with cracks around the perimeter of stonework. So I was letting in wind and rain. And then when it was coming out, it was it was bringing out dissolved calcite, which was which was then from the sea, from the lines.

00:42:49:23 - 00:43:25:19

Speaker 5

And so that's when the wall, an incredible thing that is on the face is sort of indicative of the fact that the water was going in, spending a long time and then leaching out, leaching out slowly. And the paintings that these sort of suits that sort of cut back into the into the wall, into the into the pointing and behind these sort of facing buildings that were stuck on, I think in the nineties were East of Slate paintings and east of Slate is interesting because it contains properties which offices, full schools basically.

00:43:25:19 - 00:43:54:21

Speaker 5

But it's iron and sulfur and sulfide which when saturates is for a long period of time corrode. So they rust, basically they pass, they break apart the slate and one of the products of the process of deterioration, the corrosion reaction is sulfuric acid, which then reacts with the lime calcium carbonate to produce calcium sulfate, which is gypsum, which is then water soluble.

00:43:54:21 - 00:44:46:18

Speaker 5

So this is all sort of understood through testing and analysis and inspection trials before it starts to work. And then this shows the of just the sections gaps through the wall. I think I mentioned previously that they've done a couple of projects to sort of try and overcome the issues in the seventies and the nineties. So the blue that emerged on the far left the the drawing is is the original is the most of that with so found to be a moderately hyperbolic comics line and then the Manhattan Sun in 1912 they yeah this is the place to to rebuild the wall bedding in kind of modern materials sometimes were so basically by today's standards

00:44:46:18 - 00:45:20:19

Speaker 5

relatively low strength but cement nonetheless. And in 1995 they cut into that but not all the way through it and then re points it in a kind of hydrated lime cement mix with the space buildings. This is all contributing to. Yeah, holding washing already to almost make things worse by enabling all these outside to get saturated. So yeah, the repair first, the repair involves removing problematic fabric like this image of Serena holding a enormous breaker.

00:45:21:00 - 00:45:49:08

Speaker 5

Basically that the stone is so hard that they could justify using it. Really it's a robust power source to to ship out all of the 1912 and the 1920s. Cementitious pointing back to the original building waters. So we're confident that they won't be doing any damage to the the stonework she helps with with that. And then we hoped with mortar mixing.

00:45:49:08 - 00:46:24:14

Speaker 5

So we mixed a quick lime mortar with a local sand and gauged with an IT so five to kind end up with a moderately hydraulic mortar and the pinning said use this time to reboot. That's a kind of a fresh face were caithness block of sandstone I guess in doing so they installed kind of a continuity of before a structure from the holes of the wall, the original housing to the draw in front of the face image.

00:46:24:15 - 00:46:48:06

Speaker 5

On the right you can see James and Serena inspecting some of the some of the finished wall. Yeah that that that sort of this is large areas of render render over the face of buildings and water to the building back up to the Yeah. A flush space really just to conclude I think we took away from this that it's the importance of understanding the building really thoroughly.

00:46:49:04 - 00:47:34:04

Speaker 5

So leading sets of avoiding making assumptions because the repairs evidence based really so in the sand what was causing the problems and the the the the repair reaction was, was a response to that. It was pretty clear when we met Andy Burnham Often, you know, everybody's expertise was it was pretty equally valued. It was a really collaborative kind of conversation, I guess, around the project and how they approached with announce when we think that that probably helped to kind of prevent any individual biases and sort of, you know, bias that one person might have had that might start the project in a sort of wrong direction.

00:47:35:15 - 00:47:56:19

Speaker 5

And also we feel that whatever potentially that that the way that they approach the projects in terms of duration and pace it by not kind of, you know, going it all guns blazing to do everything at once. It creates opportunities to be reflective, you know, to look at kind of how things were going, whether the things were progressing.

00:47:56:19 - 00:48:14:07

Speaker 5

I guess they as they predicted they would and, you know, the ability to kind of change tack if they needed to really needed a great deal of that. But I think it's just having having the space and the time to to to think about things and do that if needed, rather than being committing to an approach from the beginning.

00:48:14:07 - 00:48:37:05

Speaker 5

And then before you know it, you can hope everything and potentially you could have done a better job. So yes, in this last slide, so sort of say thanks to historic England for letting us also navigate presenting some of the case study experiences from the scholarship and others are this. I think.

00:48:37:05 - 00:48:58:02

Speaker 1

Yes. Thank you and thank you everyone for your lovely, lovely talks. Thanks and nice to in the site. But now what we're gonna do is we're going to pop over to the Q&A side and there are a few questions, but we do have one or two already. So I'm going to ask the scholars and Nikki and Catherine to show their videos so we can see everybody.

00:48:59:02 - 00:49:17:23

Speaker 1

I will share mine, too. So there are some familiar faces, sir. Hello. Hopefully you can all see me. There we go. Shinny Nikki. Katie Jacobs, Rena. And what we will do is Nikki, if you would like to go first, I know you have a question before. Well, first of all, thank you tonight.

00:49:17:23 - 00:49:34:20

Speaker 3

For putting into context the three technical presentations. And they were fantastic presentations. So I think the cast iron presentation was brilliant. But what we're learning obviously from that project is a little bit like what we've learned from Windsor Castle in terms of fire.

00:49:34:20 - 00:49:35:12

Speaker 5

On on.

00:49:35:15 - 00:50:00:12

Speaker 3

Products and the ten years looking at the wind driven rain issues at Duart was fantastic. But yes, my question particularly relates to reinforced concrete. I've just put into the question box some links to publications to do with concrete, not least of which are practical. Building conservation book. We're doing some research with Getty Conservation Institute.

00:50:01:08 - 00:50:02:07

Speaker 1

We're trying to.

00:50:02:07 - 00:50:11:13

Speaker 3

Focus on what we are focusing on patch repairs in like for like tools concrete rather than the polymer modified repair materials.

00:50:12:08 - 00:50:13:10

Speaker 1

So my question.

00:50:13:17 - 00:50:32:02

Speaker 3

Is at the stadium, when was the decision, what did you consider was important in the decision whether you could do a proper cast, concrete repair or whether the it was more appropriate to use a what if a polymer modified repair material?

00:50:33:12 - 00:51:01:00

Speaker 4

And so obviously this was designed as a repair designed by Steve Wood, who was leading the the repair of this building. But he he he was developing two different options. And I think it was specifically in relation to I don't know if we actually asked him this question, but I'm going to go on my own, my own knowledge of repair of buildings such as this.

00:51:01:10 - 00:51:27:22

Speaker 4

And I would say that if you're repairing a large area and you can get a good depth and you can get a good bond and you're aware that you're going to be able to like place your concrete well, so you're going to able to vibrate it, that you're not going to have a shrinkage problem. And then I would suggest that it's probably okay in those areas and sensors to use concrete.

00:51:27:22 - 00:51:53:07

Speaker 4

But you've also got to think about the differences between the proprietary products that you're talking about are normally a mortar based. So you've got a difference between concrete and mortar markers are made up of fine aggregates only, whereas concrete is you've got large aggregates and, fine aggregates. So you're talking up to 20 mil aggregate, probably a mix of a ten and a 20 for a concrete, whereas a mortar is normally a sand.

00:51:53:07 - 00:52:15:21

Speaker 4

You're talking anything up to two mils. So you've also got to think about what the cover is. So in this instance, I think that because of the issues with the actual and the construction issue, where they had minimal cover in cement in areas, I think it was only a few mills. So the proprietary products were much more suitable because they didn't want to.

00:52:16:03 - 00:52:46:23

Speaker 4

I don't think he wanted to actually remove any more material than he needed to. So I think he was really intent on keeping as much of that as possible. So he was using the proprietary product products where he felt that he couldn't get enough cover all this. So you have to think about the thickness of your aggregate. So if you've got a 20 mile aggregate and there are ten mill aggregate, maybe specifically for something like this, then you might not have that because you can't have your concrete and, you know, the actual aggregate getting caught between you on the face.

00:52:46:23 - 00:53:12:00

Speaker 4

And then that's a real easy way for it to degrade again in the future. So I think that's probably where he differentiated between using the proprietary products because they're actually designed normally as admixtures for to reduce shrinkage and the high strength and they, you know, they they're designed specifically for these things where you don't need to worry about the curing of them and they're they're normally safe quite quickly.

00:53:12:03 - 00:53:18:24

Speaker 4

You can build them up in layers. And so they're really two different approaches for two different issues.

00:53:19:11 - 00:53:28:02

Speaker 3

Yeah, lovely. Thank you very much for explaining that. Thank you. I can pass around the easier ones.

00:53:28:03 - 00:53:31:23

Speaker 1

Yeah, go ahead. Yeah, go for it.

00:53:31:23 - 00:54:10:23

Speaker 3

So, Joyce, Christie asks which engineers are working on the Glasgow School of Art so Narrow Associates is is the lead engineer on it, working very closely with Simpson and Brown is conservation architects. But what they're relying on input from specialists in cast iron for developing those methodology. So that's with Shepley in Sheffield that they've been working on with load tests and also a little bit with try these as for the for the testing, so it's a collaborative approach.

00:54:10:23 - 00:54:35:19

Speaker 1

It's very much. Katie I was wondering many phrases Christian I think is for you. Serena how you test the No no, not for you. Or is it somebody could could somebody answer many phrases question about how you test competence of cast post fire cuts guides rigid crystalline structure means it doesn't reflect much. So how do you tell if it's okay to put back in the building?

00:54:35:22 - 00:54:37:24

Speaker 4

I think Katie should be able to answer this.

00:54:37:24 - 00:54:41:06

Speaker 1

Yeah, or to her.

00:54:43:00 - 00:55:11:17

Speaker 3

And so is I was trying to be as brief as possible in the in the and in the talk. But yeah well one of the ways is doing what they're trying to do at the GSA at the moment which is you're doing a really thorough analysis of what's left there as, as a beam. And that's sort of all of the crack investigations that they did.

00:55:11:17 - 00:55:44:01

Speaker 3

So those photos that I flashed up of taking the beam out of the building, looking at it from all angles, and then actually cleaning it all down and doing they did a magnetic magnetic particle inspection, which is something that's used quite frequently in metallurgy to be able to identify cracks or anything with it. And then what they're looking at doing as where they can is actually saying that in fact that cast iron beam is we analyze exactly how it's working in the structure.

00:55:44:01 - 00:56:11:22

Speaker 3

We can show that where those cracks are located. They're actually going to be being pushed rather than being pulled apart. So the cracks themselves are are not are not going to affect the structural capability in context. Obviously, if you change the context, you change the design, that's going to be different and that's going to be very much on a beam by beam basis, because sometimes those beams will be spanning and they will be working in tension and those cracks are going to be causing an issue.

00:56:11:22 - 00:56:39:01

Speaker 3

So it's very much looking at the detail of exactly what each beam has, experience, what's happened to each beam, and what we're asking the beam to do going forward. And that was one of the reasons, even though that's quite a big claim, to say that it can still work, even though there's cracks, that's when we can resort to doing actual load testing of the elements, which is one of the things they've done with that one sample beam that they've looked at so far.

00:56:40:20 - 00:57:02:08

Speaker 1

That's perfect. Thank you very much. And with that, we have just popped over time. So I'm going to close the questions at this point, and I would like to say thank you very much to our audience for asking questions and thank you very much to our scholars who came on today and great presentations. You were all wonderful, but a few minor technical issues and my dog didn't bark, so that was perfect.

00:57:02:15 - 00:57:16:04

Speaker 1

So I think we've done really well. So I'd like to again say thank you on behalf of historic England for agreeing to give this talk today. And we've really enjoyed it. And the key. Would you like to close it? Just want to say thank you to you, Alice.

00:57:16:04 - 00:57:21:21

Speaker 3

And to Katherine for putting into context the scholarship for us. Thank you.