CARDOE MARTIN’S A-Z OF BUILDING SURVEYING PODCAST
ROOFING DEFECTS WITH GRAHAM CARDOE
Host: Welcome to the Cardoe Martin Podcast A-Z of Building Surveying, giving you the lowdown on the world of Building Surveying, in this episode we are going to have a chat with Graham Cardoe, Chairperson at Cardoe Martin. This will be our second Podcast in 2020 AC that’s after Covid, things have changed to the way we live and the way we work despite the clear facts that a paradigm shift has occurred our buildings still need care and preventative maintenance, leaks still need to be fixed and a human remains at the heart of our built environment, keep safe and best wishes to you, your family and community from all at Cardoe Martin as you join us once again for a journey through time and materials as we uncover the essentials of roofing defects. In this episode we’re pleased to have Graham Cardoe back on the sofa, welcome again Graham.
GC: Thank you it is good to be here.
Host: (0.47) Yeah, it is good to have you back on and for a different subject from our earlier conversation so we are dealing with roofing defects. So why don’t we kick off with fundamental question what is a roof?
GC: Well, a roof is the structure that covers the top of the building it’s there to protect the building from the elements, to provide thermal insulation and sometimes to allow for installation of plant such as air conditioning and ventilation equipment and roofs vary from a simple flat roof to an extension to the impressive lead clad dormers at St. Paul’s Cathedral.
Host: (1.18) What are the most common types of roofs?
GC: Well, there are two main types, flat roofs typical finishes could be felt, asphalt which is a bitumen-based material, sheet zinc, sheet lead, glass and more recently single ply membranes and liquid applied treatments and pitched roofs typically are finished with tiles which could be clay or concrete, slates natural or artificial and lead and zinc, steel and glass.
Host: (1.48) There is quite an array of different types has you found that there’s one that you prefer working on?
GC: Well I suppose it’s all dictated really by the budget I mean lead will outlast any building’s life so it’s the ideal finish for, in terms of longevity, certainly for flat and pitched roofs, but it’s impractical in large areas so you would never consider applying lead to a warehouse roof which is so vast that you’d never have the money to do it and there’d be no logic to it because the building may require rebuilding in 40 or 50 years anyway, so it’s about trying to comply with the limitations of the budget and other factors.
Host: (2.32) So are commercial and residential building roofs different to each other or they technically the same but with just different settings?
GC: Well, I’ve seen all of the roof types and finishes that I mentioned earlier on commercial and residential properties, but some finishes are far more common on particular types of building so warehouse roofs and industrial roofs are virtually all finished with profiled steel sheeting because it’s cost effective, and its purpose acquired for that type of building.
Host: (3.10) And then thinking of the defects that you come across which are the common roofing defects that our listeners would be interested to hear about?
GC: Well all roof finishes have a limited lifespan varying from 10 years for a basic felt roof to over 100 years for a lead roof, so when those finishes deteriorate they crack and become defective and need renewal and defects also occur due to poor workmanship and design, lead as I’ve said earlier, can outlast the lifespan of any building but premature failure typically occurs due to poor detailing and the most common failure of lead roofs is due to inadequate provision for thermal movement and poor design details are also a cause of failure, omission of adequate ventilation to a roof structure or omission of vapour barriers to prevent water vapour passing into a roof structure can result in rot to the timbers and warehouse roofs typically constructed of cold steel often suffer from corrosion of the sheet ends where they’re cut and not protected from corrosion and another roofing defect that is often due to overloading of the structure sometimes by installing a heavier finish such as tiles compared to original slate and that causes sag of the timbers and cracking and bulging to the walls below.
Host: (4.28) You mentioned about the thermal movement with the lead roofs, is that, well at least in my head, I’m looking at a very thick piece of lead that’s gone over this roof, is it about the building goes through a seasonal changes expands and contracts and then the lead isn’t really built, the manoeuvring isn’t there so therefore it kind of just cracks in half because it can’t cope or is it more to do with natural thermal properties of the material itself?
GC: Well all lead is categorised into different codes which is essentially the weight per square, foot or square metre probably per square foot traditionally and there’s a code of practice for leadwork and that’s stipulates the maximum lengths of lead that can be installed either in a flashing, and a junction of a roof and a side wall or a gutter which could be lined with lead and if that leadwork is laid in too long a length because it expands and contracts with seasonal changes in temperature it has to have somewhere to go and if it’s got no joint present then it lifts and cracks so that’s the reason for providing movement joints, it’s not due to the quality of the lead it’s the design detailing and construction detailing that dictates the performance of the lead in that regard and it’s well established the procedures that have to be taken to ensure that cracking and damage doesn’t occur to leadwork.
Host: (5.56) So in a nutshell most of the roofing defects could be avoided if the workmanship and design at the initial laying of the roof were better, would that be fair to say?
GC: Well subject to the fact that all roof finishes have a limited lifespan so it’s a combination of both, I mean finishes are going to eventually fail due to age and…
GC: Yeah, but another obviously there have got to be built in accordance with good building practice.
Host: (6.26) So how do you know when you have a roof defect especially if you can’t see the roof very well? Cos I’m thinking of my own house and the chance of me being able to see the flat roof right on top of the mansard is really, well it’s impossible unless I get the ladders and go up really high, how do I actually tell?
GC: Well the most common indication of a defect in a roof is water penetrating internally but the problem then is that significant damage may already have occurred by the time water comes through and plasterwork, decorations, carpets etc. will be damaged so prevention is better than cure and I would recommend that any roof is inspected at least once a year and whilst a physical inspection at close hand by a surveyor is the best type of inspection there are other inspection methods becoming more popular including drone surveys and cameras mounted on a mast transmitting video photos to an iPhone and of course mobile access platforms or cherry pickers and evidence of a roof problem may show itself in distortion and cracking of the walls which are supported which support the roofs but in most cases I think regular inspection is the key.
Host: (7.35) Lovely thank you so should I be worried if I can see a roof defect but there aren’t any leaks, or there is nothing happening inside the house or the commercial property that’s suggesting that there’s a problem?
GC: Yes it’s important to investigate any concerns of this type without delay, for instance there could be missing slates or tiles visible to the roof but no leakage is taking place internally and this would typically be because there’s an underlying of felt below the slates of tiles which provides a secondary defence against water penetration but further tiles or slates could slip or fall to the ground and cause injury to passers-by, when you see a defect to take action and investigate it further.
Host: (8.15) So does that mean that you could solve if its affecting that felt line cos I’m thinking inside a loft, you could go inside the loft in your house/property and you would be able to see that the line perhaps has been penetrated by something sharp if it’s full and on it, smashed the tile etc. is that something you can do if you’re unsure and you just want to double check or would it be better to get a surveyor in?
GC: I don’t think you could really identify the cause of the problem from within the roof space because you wouldn’t be able to penetrate the felt without cutting it and that wouldn’t be a good idea so a lot of problems with the tiles or slates externally could be due to the age of the tiles or slates or problems with the nailing of the slates which could becoming corroded or defective, so I think an external inspection would be the best way forward in that situation.
Host: (9.03) And talking about the cost of things are roofing defects easy to repair? Is this something that I’m really going to have to start saving up for just in case it happens?
GC: Possibly yeah, I mean this depends really upon the extent of repairs that are required and the height of the roof above ground level, it’s important to remember that whatever repair is required safe access has to be provided and this may include an access tower or perimeter edge protection which increases the cost of the work and this is because a significant proportion of injuries and fatalities in construction are due to falls from height. So safe access has to be provided and that can significantly increase the cost and a further problem with roof repairs that there may be hidden damage which only becomes apparent when the surface finish is removed so there may be rot to timbers that become evident once you take the roof finish off and this obviously increases the cost especially if the rot has become quite extensive, and a further consideration with existing roofs is that depending upon the extent of repair it may be necessary to upgrade the thermal insulation to comply with current Building Regulations, and that would.
Host: Yeah, sounds a good idea.
GC: Well, it is mandatory in fact for existing roofs above a percentage of the roof needing to be replaced so that is important and with that there is a requirement that Building Regulations Consent would normally be required for that kind of work or for other work of a structural nature as well so that can also increase the cost and require some professional advice as well.
Host: (10.42) So is fixing roofing defects quite a long job cos now I’m beginning to see that there could be a lot of people on the roof for a long time or are a lot of them fixed in relatively short space of time?
GC: Well it will vary it’s possible to do a patch repair I suppose if it’s a specific localised defect but at the same time you could maybe think it was just a localised defect but once the work starts find out that it’s a more extensive problem and wholesale recovering could be required, it’s quite a risky area really roofing repairs because of problems of access beforehand to establish the full extent of the problem and the likelihood that there are hidden problems once opening up is undertaken which increases costs, so it’s good to have a contingency available for issues of that type.
Host: (11.26) Lovely thanks Graham, thinking them from a surveying point of view how does the surveyor add value, now I just think well if it’s a quick job why don’t I just get a builder or a roofer to look at the roof defect, what is it about surveying as a field that can return on investment here?
GC: You can instruct a builder to look at your roof, if you know a builder you can trust 100% and is competent but you must remember that builders make a living by carrying out building work not by surveying roofs, so they have got a vested interested in actually undertaking work.
Host: Yeah, that is a good point.
GC: And a further point is that a builder may not be aware of the requirement to upgrade current Building Regulations he may also require a Specification of Works, so the safest option is to obtain an independent professional opinion from a Building Surveyor. In terms of a surveyor adding value, I’d say this is by giving independent advice and offering a solution which is compliant with Building Regulations and Planning which meets the client’s needs and budget.
Host: (12.29) So just going back to the Specification of Works comment you made a second ago, what you’re basically saying is that if I had the builder around to have a look at it I’d still have to tell him or her what to do anyway so I might end up having to pay for an expert to come in and specify the works that actually had to be taking place and then they would carry out those repairs, is that what you’re saying?
GC: He might not necessarily choose a system that is best value or the most suitable system for a property, he might choose a system that he uses quite a lot that he likes, or that his tradesmen are skilled in performing but that may not necessarily be the best solution for the job.
Host: (13.09) So what shall I do when I have a leak or notice a roof defect at my property?
GC: Water penetration or leakage is one of the main threats to any building and this is because water not only damages finishes but it causes rot to timber and corrosion to steelwork and defects of that type are costly to eradicate so the best advice is to report the problem to a property professional as soon as possible and if you’re a tenant I would report it to the managing agent in the first instance and then they can appoint a Building Surveyor to investigate further. If you’re an owner/occupier or a freeholder or a lessee with a repairing obligation I would appoint a Chartered Building Surveyor.
Host: (13.50) Lovely thank you Graham, just one final question from me is have you ever come into contact with thatched roofs a lot and are these things that you would sort of recommend, have you worked on them, is a building surveyor still required on a thatched roof or is it something that you would go back to the thatcher?
GC: No very much so, I mean, I think the percentage of thatched roofs out of the total roofs is relatively small inevitably in a building surveyor’s career you don’t survey that many thatched properties but I’ve surveyed quite a few and interestingly the statistics indicate the fire risk isn’t any higher than traditional roofs but I mean there is certainly quite a bit of advice to be given there in terms of the type of material that’s been used, reed compared to straw obviously have different lifespans and longevity and obviously when you survey a thatched roof you can observe defects in terms of deterioration of the thatch and whatever and there have been times when I’ve undertaken surveys of that type and recommended that quotes are obtained for repairs so there’s certainly a role to be played by a building surveyor in terms of roofs of that type without doubt.
Host: Lovely thank you, so you have been tuned into Cardoe Martin’s A-Z of Building Surveying Podcast. Thank you for listening and thank you very much to Graham Cardoe for joining us today.
GC: Thank you it has been a pleasure.
Host: And for sharing all your experience and knowledge on roofing defects.
GC: No thank you I’ve enjoyed the Podcast.