Parapet Walls - Are They A Good Idea?

Roger looks at the pros and cons of parapet walls.
Check out the Steve Roofer channel and London Flat Roofing.
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[@American-In-Mykolaiv]

Great explanation of "thermal siphoning" - most of the houses here in Ukraine have no insulation, so the little house we bought got an upgrade - first the ceilings got two layers of rock wool, about 30cm, then the sides of the house were covered with 10cm foam and stucco, then I extended the roof by one meter all the way around, so I could wrap the corners with foam and cover it with under roof rock-wool. There are no cold spots, therefore no condensation. For winter windows I added a third layer of clear plexiglass with wooden frame to the outside of the double glazed windows. Little condensation around the glass edges in the kitchen and bathroom. Sure keeps from sending gas money to Putin. Love to watch your videos, you get to the point without much ado and tell it like it is. Thought about heat pumps, watched your videos and will hold off. Best investment were some solar panels, a low frequency inverter (6KW) along with 800AH LiFePo batteries - reduces my utility bill by half, except for winter months. Thanks for your videos!

[@MargotDobbie]

"Sending Gas money to putin" . Without Russia you would have no Gas. Cant wait for you to be humbled when they invade lol

[@g7vqedave2]

@@MargotDobbie Yep, thank Russia for allowing people to carry on warming the whole world by still burning gas.

[@michaelcoles6140]

@@MargotDobbie how do you find an invasion funny! Russia just wants to flex its muscles but will soon realise it has only just started to get muscles and will full within weeks… funny how you go by mindful but are just mindless…. Hope you don’t get run over or anything and can live in peace you complete idiot.

[@normanboyes4983]

@@MargotDobbie A rather unthoughtful reply. When Putin invades Ukraine - what do you think will happen to the energy spot markets? The answer is the price of gas will rocket and unless you are 100% off grid and grow all your own food you will be 100% impacted.

[@justicecase19]

Mindfull, hmmm I'm assuming your name is ironic.

[@GavinLawrence747]

but I want somewhere I can peek over with my browning machine gun when the Chinese or Russian paratroopers are running up the street....... oh wait no!

[@franklinkarrass5830]

I knew nothing of parapet walls. Although I have seen them I never knew the nomenclature. You pointed out some very informative problems. Thank you. 👍👍

[@kelstra1997]

I like your solution Roger and it's pretty much how a competent Architect/Designer would normally detail it. In Australia we don't have as many dampness condensation problems as you have in the UK due to our warmer climate - we certainly have them but not as often. Over here, concrete roofs are not all that common, we certainly have a few parapet walls but usually in conjunction with metal deck roofs. Before I retired I worked in the Architectural profession and I have detailed many parapets in my time. I am pleased to say however, that I can't think of a single instance where they gave a problem. I would say that trying to flash into the face of brickwork at a DPC is always fraught with danger and we always detailed our parapets with the roof flashing carried up for the full height of the parapet and over the top and almost always in conjunction with a stud frame as the inner part = exactly as you explained.

[@JamesBrown-mt5ru]

Perfect timing! Roofer asked me today if I wanted to retain the parapets. He explained the situation exactly as the video. I now feel knowledgeable.

[@dryfixpreservation]

Terrible advice here Rodger. How do you propose to tie In your cavity tray at the head of the wall to the inner timber frame wall? Also what stops condensate forming in the cavity above roof level and decaying the timber frame? Where is the timber frame gaining its stability especially if its taller than 300mm? How do you ensure continuity between the cavity wall insulation and the roof insulation when constructing a warm roof design? A far better sution would be to stick with the traditional method of construction, build the parapet to NHBC guidance and simply use an insulated internal lining to remove the cold bridge. Come on skill builder I expected much better advice than this!

[@chrisr1254]

Agreed. This is basically an admission that this particular flat roofer hasn't read or conformed with the British Code of Best Practice for Flat Roofing. You won't find a single manufacturer recommending a similar 'fix' as demonstrated here, because the solution is very simple and well-documented, if you install the flat roof and upstand insulation correctly. "There's cold bridging here - because I didn't install the flat roof correctly; here is a massively over-engineered solution I've thought up!". I recommend some reading up here - BS6229:2018, NHBC, LABC or Premier Guarantee guidance documents as a starter for ten.

[@effervescence5664]

That's a clever way of solving the issue, similar to my old builders which follow Joe Lstiburek's building science "perfect wall". As long as the Water > Air > insulation barriers are all joined and layered in that order it minimizes and in most cases removes the issues.

[@kevinrae3299]

Roger is correct about taking insulation up the parapet wall, I always make sure I take the membrane up , over and down 20mm . So as the roof is water tight without the cope/capping.

[@BerkeleyTowers]

Yep, absolutely agree... I closed the parapet wall and applied exactly the same treatment to the parapet as the actual roof ( in my case a liquid membrane). In theory, I shouldnt need the coping at all, but if course it's a big design aesthetic point. But crucially, the coping is only the first line of defence....... not the only one.....

[@lambjf187]

It needs the insulation standing up on the inside of the parapet wall and then the roof membrane covering extended up and under the Cap stone. Will require extra width on the cap stone to accommodate the increased depth of the parapet. Excellent rant Roger.

[@peterdallyn6440]

Totally agree, a lightweight stud wall would work but if timber it'll start rotting pretty soon. Plus the outer leaf of brick is supported on a very weak element, probably not an issue if the parapet wall is low, but if a reasonable height it would be quite weak. I agree to keeping the inner wall in masonry, but adding an Insulated upstand behind the single ply. Rogers point is really well put though, this detail is so often overlooked by designers \architects.

[@harveysmith100]

That was a very good explanation Roger. As a bricklayer I would like to add to this, the increased specification of concrete blocks rather than thermalite blocks. Yes they are stronger but they create a real problem with cold spots. Your example is a classic case, if the inside wall is made of concrete blocks the cold spot would be far worse than if the internal wall was built out of thermalite. I suspect dot and dab is also far worse than a light weight plaster too.

[@deanmsimpson]

Do you believe thermalite blocks would stop the 'cold bridging' Roger speaks off? Therefore not needing to build the inner skin out of stud-work?

[@harveysmith100]

@@deanmsimpson You would have to check with an expert in thermal values but thermalite blocks have a great thermal value. Many years ago we would build houses with no cavity wall insulation using 100mm thermalite blocks in the inner skin. This met the spec as it was back then. Chances are they would solve the cold bridging.

[@deanmsimpson]

@@harveysmith100 Yes, very interesting. I prefer the idea of having the inner skin of the parapet wall being constructed from solid blocks as opposed to stud-work. Thank-you for your reply Harvey 👍

[@londonengland7096]

I have a 40 year old extension built of 1 single therma block wall and cold roof that had that loose wool type insulation and no vapour barrier iI never once had any issues until now when I got it redone

[@NitrousAvster]

There are new load bearing insulation blocks (like Marmox Thermoblock) that removes the thermal bridging and is rated up to 9Nm. Currently using it for an extension project below DPC and parapet.

[@SkillBuilder]

The 9nm block is not a great insulator. You could use a 2.8Nm on that inner skin above the roof line. Good point though

[@Rob-tg7nr]

came here to say this, not sure on their reply

[@robinbennett5994]

They also sell a heat resistant variety especially for parapet walls. The regular stuff can melt if the a bituminous membranes is applied with a flame gun.

[@designcoordinationmanageme3177]

The thermal co-efficient of aereated blockwork, whilst better than dense, is only about 1.1 vs 1.2 ... when you do the calc's, it alters the U value very little, and only insulation has any real effect. For comparison, insulation is generally 0.4 for the poor stuff, 0.2 for the good. Insulation only needs to be part way, if you do thermal model contouring it will show a point where extending the insulation after that point is of nil effect. Insulation is key.

[@sonandmoon2958]

​@@designcoordinationmanageme3177 love, love love it, new your talking my language Padawan

[@Tensquaremetreworkshop]

I have a couple of neighbours with the same story. First the roofer replaced the leading (sloping warm roof with parapet) then new coping, still condensation. Massive job to fix, so they have to live with it.1960s build, so originally it did not have heating. Cavity wall retro-fill. You have nailed the reason.

[@68bwild]

They've been the rage here Down Under for the last 20 years! So there's been plenty of leaks in that time, few guys know how to construct them properly and even fewer plumbers know how to flash them and sort out correct sized drainage. We don't/won't have them on our houses!! Keep up the good work Roger.

[@master_Blaster91]

Do plumbers do the flashings for roofs down under still ?

[@68bwild]

@@master_Blaster91 Yes in theory :)

[@supervitz7178]

Interesting video. We built a large extension about 20 years ago with a parapet wall. It's still on its original felt roof and we never had any issues with moisture ingress. We keep thinking about replacing the felt because it's technically at the end of its design life, but we inspect it every summer and it's completely fine. I can't even justify changing it to GRP, since the felt has lasted so long. I think your opinion is a bit too harsh on parapets, but I hear you.

[@randomtask9029]

Good stuff. Glad you mentioned roof overhangs. The first thing I look at on a building is whether the roof overhangs the walls and how far out it goes. The overhang is an enormous asset in preserving the condition of walls.

[@TheBrick2]

Timber house in that harsh Norway climate have a good overhang and last hundreds of years, makes all the difference. Good hat, good shoes.

[@TurinTuramber]

Some bedded verges on the gable end only overhangs two inches. Must be lucky with the weather.

[@nickdrummer1992]

Thanks so much for explaining this Roger! I've had this EXACT problem in the garage of an extension we finished recently and couldn't work out what the f#%king hell it was!!! Well at least I now know how to rectify the problem. Will be looking at this detail a lot closer next time when building / going through the architectural drawings. Cheers from Australia mate, Nick

[@jonofham6658]

"If you don't know what a parapet wall is, then why are you watching this video!?" Roger, you are a legend.

[@ra4yu]

There is a really good video by stewart hicks on flat roofs that goes into quite a lot of detail. The problem here doesnt seem so much exclusive to parapet walls as a conflict of older and newer construction where insulation and air tight design mixed with older methods often leads to problems like condensation, mold, siphoning and trapped water in the event of leaks.

[@normanboyes4983]

Thank you for doing this Roger and the consensus view of the comments thus far is that you have nailed it. However, I am surprised that you did not consider adding a heat pump to sort out condensation problems. Taxi! 😉👍

[@paulhaggett3710]

🤣🤣👍

[@JohnnyMotel99]

I lived in a 60's low rise block, with a flat roof. This was a concrete slab construction, with brick piers. This was before expansion joints as well. The flat roof always gave problems for the top floor flats. Block spent a lot of money on re-roofing with a specialised covering. I did suggest that the block get planning permission for a butterfly roof constructed on top of the old flat roof, since the flat roof sloped to the middle where all the drainage was. But the block went for the cheaper option.

[@sasa1982uk]

Good opinion, I will use this when I build my house in the pacific, parapet walls are good for cyclone proofing.

[@letzrockitrite8469]

US builder here Roger... Great fix for a poor design.... nice to see a no nonsense info vid about this design. On a parallel thought concerning wasteful/design/building etc.. We've built 4 plexes in Fla. where the entire design is about eliminating waste, for instance the rooms were designed so that you could hang full sheets (using 12 footers) where the rooms were 8' or 4' or 16' or 12' ... the outside of the building was the same..... the scrap pile was (for a 4 plex mind you) fit in the back of a pickup truck.... I love that concept.... another great design is a rectangle building (so the roof's cheapest design's been achieved), with a 9ft ceiling downstairs and and 8 ft. upper.... have an overhang coming out all the way around the building from just under the windows extending out 6 ft. all the way around the building which overhangs a 6 ft. deck. This design gives one that solar heating in the winter and cooling because of the over hang. The look's usually dolled up with the hand rail etc... the economy of this design can be further extended by consolidating the plumbing by running a common plumbing wall with the bath and kitchen below and the baths above. anyway... always appreciate your videos Skill Builder... Jon O @ Idaho

[@SkillBuilder]

That sounds like a good idea, it would be good to see some pictures.

[@ndewhurst1007]

Roger, I love parapet walls when they are built correctly. Especially when built on a rear extension as a party wall. It allows the neighbour to abut the wall at a later date at perhaps a different height from the first neighbour and without interfering with their roof covering. But they MUST be built correctly.

[@SkillBuilder]

Perfect party walls in roofs were a fire regulation and, as you say, done right, there is no problem

[@pauledwards9493]

So many schools have this problem. Some think a topping stone will do, its not a dam wall outside a house

[@andrewwilson3663]

Parapet walls are pants. Agree with everything you say Roger, been there, done that! Had an old stone house with one that had signs of numerous repairs. Closed the cavity with code 4 lead with a massive skirt to cure it. My daughter now has a new house with some capping details and they have lifted and slipped already. One day they will be on the doorstep if she doesn't get them fixed.

[@mattylad8035]

Whilst I have no need nor likely never will need a parapet wall, this was a very good explanation of what to consider should I ever have the chance to have anything to do with one (hope not). Thanks.

[@livingladolcevita7318]

I would run away from a flat roof. My in-laws have one on their extension, nothing but problem after problem with leaks.

[@spyrosspyrou5809]

Excellent stuff! I've been a plasterer, tiler, plumber, electrician and carpenter for many years now and consider myself to be experienced, talented and knowledgeable but I still learn something new from all of your videos. Keep up the good work!

[@YipeeKiYayJB]

Steve Roofer's videos are the absolute best when it comes to all things flat roofs. Great if you could get him on for a discussion on flat roof construction techniques.

[@SkillBuilder]

Great suggestion! We did ask the question some time ago but he didn't reply. I guess he is happy doing his own thing

[@tinytonymaloney7832]

Good vid Rog but I wouldnt mind some photos of one you done earlier. Got to do some 1200mm high PP walls on my back extension if I get it started this year as a wind break for a first floor balcony. 😁

[@8bitsim]

A great topic Roger, there is certainly a lot to discuss when it comes to parapet walls. You didn't mention anything about cavity trays, if you can put a cavity tray in above the roof junction this ensures that any water that gets in above is directed out and they are certainly prone to failure. I suspect that many instances of condensation are caused by the wall being a little damp and reducing it's insulation value leading to condensation. I liked your idea of continuous insulation but I don't think it is good to build the structure off the insulation deck, it would be more likely to move and has no strength in tension not being anchored down. It might be better to fix the studwork to the roof structure and then insulate between the timbers, this would introduce only minimal thermal bridging but would be a lot stronger. Another issue is that a stone capping on a timber and masonry construction would move and likely crack the joints so this detail would work much better with a dry fix capping system

[@SkillBuilder]

We have a video on cavity trays.

[@JohnJKelly-of4dc]

I'm going to put down prestressed slabs and put a mass concrete parapet wall and a railing. For a balcony. Obviously I'll have to put a screed over the slabs, some form of damp proofing which will run under the mass concrete...I'm trying to work it out. Make sure it's waterproof, I will have issues with thermal bridging...there will be a ceiling below the breton slabs, and lots of insulation, and the internal wall will be well insulated too..I'll work it out

[@dennisleprevost5975]

Hi Roger, I really enjoy watching your videos. I am awaiting planning permission for a flat roof extension with a roof terrace above. I’m keen to use a warm roof construction but I have been pondering how best to install the balustrade. Having watched this video I believe the parapet wall with the stud wall on the inside might be the best option. I would welcome your thoughts. Thanks Dennis

[@outlawgamingrp]

The problem isn't the parapet, it's all in how you handle flashing/insulating it. Your solution will work, but is really only an option for new construction. You seem to be talking more about existing buildings and reworking the deck and wals like that is pretty impractical. The best solution in my opinion is to add rigid insulation board to the inside of the wall. I see this even in New construction. To build on that, encapsulate the wall completely with a thermoplastic single ply, ditch the stone cap and terminate on the outside wall. This will leave your wall water tight alot easier.

[@twasb2000]

Alternatively you could insulate the exposed part of the wall

[@SkillBuilder]

Yes it would add width so it would need to be worked out in terms of the capping

[@twasb2000]

@@SkillBuilder There are also many alternatives to cavity wall construction that help eliminate cold bridging. the devil is in the detail and I wouldn't choose a flat roof for a domestic building.

[@AWilliamBishop]

Cheers Roger, very helpful buddy

[@lazylad8544]

Great demo. Absolutely gem of a video. I wouldn't of learnt anything today without that video👍👍. Top man rodge.

[@mickgascoigne4003]

Ahhhh god I start my build tomorrow and still can’t decide No plans done as it’s permitted development so got time till it gets to wall plate height

[@Paul-XCIV2]

Moncouche render and no roof overhang is the design trend that needs to FOAD.

[@SkillBuilder]

I feel the same way

[@Me-zo8yc]

Redrow did some flats near me, I know the exact look Roger means. They look awful after not long, water and extractor outlet residue staining

[@james.telfer]

Great video, saved to my house design playlist for reference!

[@SkillBuilder]

Glad it was helpful!

[@phil2544]

I've got a parapet wall, it's a pain in the a**e. I'll have to replace the lead it behind it this yr.

[@thetessellater9163]

Try GRP instead?

[@reubenklang3968]

Good video, seen loads of these roofs and always thought they looked good. Didn’t know about the issues with them though, again just comes down to that state of builders in the UK these days. Hard to find good ones now :(

[@londonengland7096]

Can dehumidifier control condensation in cold roof kitchen/bathroom? Thanks in advance for any advice

[@water__damage]

What is the specific building regulation and/ or british standard that dictates that one MUST use a cavity wall closer on a parapet, under the DPC and coping?

[@SkillBuilder]

There is no regulations. I don't think I suggested there was but it just gives some support for the membrane. You could do it with anything but a cavity closers sits in there nicely.

[@wheres_bears1378]

They look great but I would never do this if building a house, that water needs to get away from the house as fast as possible, traditional roof is best

[@richardhiggs1]

I have an old house with solid walls and a parapet wall.... How can I insulate the parapet wall and will it have the same effect as would a cavity wall ?

[@chrissmith5148]

What if you have railings on top of the coping? how do you prevent ingress through the bolts?

[@ianarmitage3518]

Makes sense,thermal bridging in that area is easily missed,and missed diagnosed. Good video cheers

[@VKDrumsHD]

I am adding an extension to my garage / workshop and have no choice but a parapet roof due to 1m from boundary, maximum 3m high. I am using floor joists so it can also be used as a roof terrace and planning 300mm high parapet (including 75mm flat coping) as i want to add stainless / glass balustrades for safety and privacy. As the terrace wall will be very low (30cm), could i run a sheet of insulation between the inner skin of blocks and flashing / grp wall flashing? And flash the entire wall up to the coping? I'm concerned your inner stud work idea won't have the same strength for my glass balustrades as double skin concrete blocks, especially if there's a high wind. The room will have a garage door so i don't think it'll get particularly hot in there when it's cold outside. Any tips or advice appreciated! cheers, Alan

[@crosslink1493]

Hello from California. Good content. I'm used to seeing them built in commercial multi-tenant buildings and row housing developments, they're usually used as firebreaks between the units in the building by extending firewalls 2-3 ft above the roof surface to keep flames from jumping along a roof. I've never seen a house with them as a decorative element.

[@MadRat70]

They are not uncommon in stone mansions. That is probably an uncommon design in California.

[@JamesParus]

During 70's flat roof buildings was common thing in Finland. Not a good idea with snow. Many of these houses later made real angled roofs. One thing we dont understand in Finland is UK style short overhangs. Here all the houses have around 50cm overhangs so the walls dont get rain.

[@utubeape]

Good solution. What do you use to bond the coping stone to the membraned half of the top of the inner parapet wall?

[@SkillBuilder]

Any polymer adhesive will do

[@ArtOfHealth]

I own a 125 yr ol commercial nearly low pitch flat roof. The city recently put 4 4x4' skylights. They worry me. I want the city to do something to prevent their seams in the skylights from leaking in to my building. We had a weird twister last week and 1/3 of my roof was ripped up. Flooded half my store. Angry.

[@SilverTrowel631]

I'm a brickie who hates parapets but some clients/architects/building inspectors love them so here's what I've done in the past. For a flat roof, build your parapet no more than 150mm above the highest point of the roof. Get some insulation board. (25mm should do) and no nails (Or similar) it to some 18mm ply. Then no nails it to the inside of the parapet (Obviously cut it to shape), ply side out. Then when your roofer lays the roof finish material (Felt or whatever), tell him to take it up the 18mm ply and right across the top of the wall (Over the cavity, ensuring it does not sag) and onto the outside brick/block skin. This will make the standard wall width approximately 350mm. Bed a suitable DPC and coping stone on top. The DPC won't sag and allow water to build up because of the roof material covering the cavity. (The roof material does not usually have the same lifespan as a DPC and it can break down slowly over time, that's why its important to use a DPC). Job done. It's possible to repeat this method on a pitch roof build but it takes a little figuring out and planning.

[@23sunderland]

Terrible design limit the escape of water roofers nightmare

[@pauldavies5655]

i am a roofer for over 30 years and i have converted quite a few flat roofs to walkways and garden space, play areas etc. lots of customers ask can they have a brick/ block parapet because it look s nicer ( and it does ) , i allways refuse and get them to have RAILINGS instead otherwise i will not do it because your name is mud after condensation like you have shown . PROBLEM SOLVED !

[@JadeBoily-c2o]

Really great video to better understand the vast world of parapet walls. Many times in my life I’ve tried to make some quality parapets, unsuccessfully. Now, with your great explanations, i will be able to do so. Again, thank you very much. I Love you Roger. Deeply. I would like to feel those steady hands on my body.

[@JamesMears76]

I hate parapet walls, had the one around my flat roof removed, it was letting water in down the wall, etc, much happier now it's gone and had the felt roof replaced with GRP

[@FanOMisery]

Not really a Fad, you see these on Georgian town houses , as Fire breaks in Victorian terraces and 1920s art Deco. I prefer to use a insulated OSB board on the inner brick face and capping, and cap with roofing material and proper drips. Also Masonry all the way up on both skins. The joisting becomes complicated at the edges otherwise.

[@quinnjin2]

In New Zealand we had a stupid fad of "mediterranean style houses" made with monolithic (cement board) cladding. We live on a famously rainy little island. ( not that little, bigger than britain in reality, but with orders of magnitude lower pop of course) ... anyway so we had this leaky building issue all through the 90's and onwards, the fad was also for untreated framing. Of course, it all turned to shite, the water would get in, the framing would rot, and basically in many cases there was no fixing it. The whole house would have to be scrapped, of course low pitch roofs, including parapet roofs were a prt of this look, with no eaves. My grandad saw all these going up, he was a master carpenter, anyway, he said at the time, there is going to be a huge problem with these buildings in a few years time... he was absolutely right of course - a recent analysis showed that a huge number of our housing stock is in jeopardy because of this ludicrous fad. We don't live in the hot dry mediterranean, and it's not rendered masonry, it's a fake copy, and it turned to custard. Now the worst thing about this was, a lot of builders got blamed for it, when in fact it was the regulatory bodies, captured by corporate interests, who passed these building system and the associated products and consented them, and the architects who failed to spot this issue, might have been better if as part of their degrees they had to do some time actually working on site... anyway.... One of the biggest culprits was also the monolithic cladding, which being cement based, doesn't flex, unlike wooden framing which does... so te screw holes opened up at the fixing points of course, which is often where it started, no eaves... wet walls, leaky fixing points, untreated framing, you get the picture....

[@MadRat70]

It sounds like you are focusing on brick-faced wall problems in general. You just happen to make the topic about parapets. Your topic has nothing to do with the roof. Honestly, most parapets in the states are over 8" block. Your perimeter to hold down your roofing typically ties into wood fastened to the backside of the wall so that counter-flashing covers your termination bar. So your roofing is never attached to the coping. Sometimes coping metal will cover the term bar, but it typically is used over wood caps, not stone. With metal coping (aka cap metal) you fasten front to back using anchoring under the face metal, referred to as clip metal or cleat. Unless you have a smooth face for the clip metal, you are going to have air penetration. And only really in that situation would it be a roofing problem. Otherwise by definition, coping stone is an engineering problem. Coping stone has a roofing function, but the engineer has to sign off on any changes to it because it is a structural component, tied to weight-bearing on the wall. No roofer is taking on that responsibility.

[@virginiabrown4281]

Our 30 year old house has a separate garage with parapet style roof, it's uninsulated but that hasn't stopped the ongoing problem of leaks. Parapet incorporated into roof design is bad because it's so easy to get a faulty, problematic result. We have just replaced the roof and now must find a carpenter that can address the parapet because as described in video the roofing isn't even the real problem. Even though we aren't dealing with insulation and condensation, addressing the coping stone or top of parapet in video was very helpful. I can only fantasize about ripping out roof and redesigning - I hate our parapet roof!

[@designcoordinationmanageme3177]

Parapet walls work well on ownership boundaries, where roof overhang & gutter would either be on neighbouring land, or if brought back to boundry line, loss of floor area within the building to move external wall back to facilitate overhang negates any benefit ... provided built correctly. Never liked coping stones that are not mechanically secured in some fashion, as you are supposed to put them on a dpc, which could act as slip plane (wind uplift).

[@tombrehony6277]

The sealing of the cavity wall as it turns into two external walls is always problematic . Why not do as was 30/ 40 years ago. Tray damp or slate sealing the cavity, Then revert to a 9inch wall. Then put your insulation on the outside as you show in your video. I've seen the 4inch wall , it's a liable to cracking....Great videos. Thanks.

[@PhotonHerald]

Very easy solution. Better air exchange and dehume. Also, insulating all the way up, instead of stopping at the roof level will stop this behavior.

[@satefutingatgoogle]

Thank you for our content. I would use external insulation on the inner layer of the parapet, which will stop any cold bridging. This method works perfectly in countries where the winters are very cold, and the autumn is very humid. Your solution is very good, but it makes the detail too complicated.

[@bigjonS4]

Roger slowly morphing into Dominic Littlewood. Don't Get Robbed Get Rodgered. Erm, maybe not...

[@SkillBuilder]

Roger the verb.... the old bugger

[@paulgodwin85]

Hi Roger I have just seen your video and was wondering how you get the air flow Across the roof if you are sealing everything up and under the coping, as the parapet walls won't allow any air flow, this will cause the roof to sweat and produce black mould.

[@tullgutten]

Didn't know what it was before now. Never want it or have it. But basicly a "quick" easy repair for this could be to insulate the highest outer innside part with lets say 5cm insulation and then do the roof/parapet wall water proofing again in the corners/walls and have a bigget top pice to compensate for the extra 5cm to stop the cold bridging. It is always fun to see something new and learn what NOT to do in the future 😅😁👍

[@tomek]

With Steve from London Roofing mentioning the current recommendation is to not place OSB/ply over the insulation (under an EPDM membrane), how would you attach the parapet studwork on top of the insulation?

[@SkillBuilder]

Hi Tomek I really don't understand what Steve is saying. The EPDM can't stick straight onto the insulation unless it is ply faced. I will look into it but I always lay the OSB 3 T&G then stick down the EPDM.

[@pitbladdoassociatesltd]

Parapet walls are no different to any other wall or part of a building. Its all in the detailing. You can have as much insulation in a wall or roof as you like, but if you allow air to penetrate and surfaces that allow dewing to occur, then it doesn’t matter about where insulation is or not. Like you mentioned cold bridging is a detail that needs addressed. Continuous layers. There’s no point having VCLs if they are being continuously punctured, and not allowed to be resealed. Mechanical fixings creating highways for cold to run along them. One of the worst details I see is plasterboard installed directly onto foil faced insulation. The foiled being a surface where dewing can and does occur, yet no air able to ventilate that moisture in or behind the plasterboard. The insulation has turned from being a reflective insulation to a conductive one, where the insulation then starts to absorb more heat that it would’ve done if there had been air space in front of it to reflect the heat back into the space.

[@IzzytheBricky]

Brilliant video mate! Love the studwork idea rather than turning the internal blockwork into external above the roof. I've did a small parapet wall Friday. However the way it was set out allowed there to be no cold spot.(I think) Overall the wall was 410mm. Face Brickwork tiny finger gap then blockwork then 100m cavity and internal blockwork. Once above the roof line, I returned my Brickwork onto the finger gap blockwork, as in theory that is still an external wall🤔👌 Worked well, but at alot of extra cost. Great video as alway mate

[@SkillBuilder]

That sounds like a really good way of doint it

[@lovenottheworld5723]

You build it in a warm climate where you're actually going to use the rooftop as living space. Who would use a flat roof in higher latitudes. The covered patio hasn't even caught on yet because it's too cold nine months of the year.

[@timcorbyn8034]

I know this comment is probably in the wrong video, but have you/will you be doing a video on soundproofing? I'd love to get a few ideas. Thank you 👍

[@l0I0I0I0]

Yes I think the term is thermal bridging. Best done by connecting all walls, ceiling, roof with external insulation, physically and thermally connected outside the main structure behind the cladding, etc. Water condenses on cold surfaces. Remove cold spots, no condensation using thermal bridging.

[@uittyman]

Great, educational stuf to consider before getting to that point. Watched it twice

[@janstafford1490]

spot on guv it should be made gospel i see so many new build houses no soffit and a flush to wall gable where architect cum accountant have become the 1970’s car salesman oooops person despite man being a species not gender keep it coming good man (gender this time)

[@sonandmoon2958]

Deuteronomy 22:8 When you build a new house, make a parapet around your roof so that you may not bring the guilt of bloodshed on your house if someone falls from the roof

[@23sunderland]

Great taught me something about the improved design but its always old parapet walls on OLD BUILDINGS

[@alanyoung7532]

Good demonstration as why one should try to avoid parapet walls and where these cant be avoided make sure you eliminate cold bridging. As you pointed out people do not realise that condensation often gets worse locally on areas that remain cold after the house generally has been thermally up[graded. The denser the internal masonry leaf the colder it is therefore the more condensation forms. Parapets and just not a good idea as sooner or later the rainwater outlets become blocked which can lead to formation of a pool on the roof, and leakage to the interior.

[@sandranewman6010]

I’ve got that problem, we had Roy Rogers and Billy the Kid build our extension (badly as well) they took all the cash and don’t answer the phone now! At some stage I will need to get it sorted, but you are 100% correct in what you say Roger, great video as always, thank you.

[@marquisdemoo1792]

How do you handle where a flat roof butts up against a wall, typically a single story flat roofed extension on the side of a 2 storey property? BTW hate parapet's too but I'm stuck with them and they are solid stone and cement capped.

[@jackturnermx6176]

I also do not like to see parapet walls I think they are a lot less weather proof. I’m a bricky and more and more we are seeing parapet gables! I absolutely hate the idea of these they are like a wind sail in my opinion as proven in that video where a pedestrian near misses being crushed by a falling parapet gable on a windy day

[@dustyjoe8071]

After watching your video on parapet walls my grandson has just bought a house with a small parapet wallto the front ofthe house between him and the next door niebour there is a drain hole for the water to escape at the bottom of the wall the trouble is the leaves get in amd block the drain the water fills up and flows into his house under the eaves this does not affect the neibourwe can seal off the brickwork under the eaves but I think us doing that the water will then go into the neibours house I think his wall under the eaves i slightly higher than ours but once we seal ours off the only place the water can go is over the parapet wall at the front or into the neibours house

[@projectbuild9784]

Down the line, the mortar between the copings falls apart. Have ended up doing lines of metal flashings over the top of copings because they are such a source of problems on a 1950s building.

[@yevgeniyshawyer2767]

Im well experienced builder but you have my thumbs up!!!

[@coronaphone710]

Yeah, but aren't they great where flute players can sit on, whistling their flute music with their legs crossed to keep balance.

[@SkillBuilder]

Good point well made

[@bikerchrisukk]

It's belt and braces, but wonder if a cavity tray might help, situated below the inner stud parapet and down a couple a courses to external wall - so even if it fails, it could drain to outside wall and never touch internal inner wall?

[@MarkizVonSchnitzel]

Why not just insulate the whole parapet wall? Extend the insulation form the roof to the outside wall?

[@Jackzuk]

I got an art deco house with a 44sq roof terrace with parapet walls, whole house is solid with no cavity and got to say ive never had any issues with what your saying. Needs a re render and am weary of silicone based renders staining i must say due to little overhang like you say.

[@AZBADBOYz]

High density spray foam base coverd in silicon coating up and over the parapet wall top and under flashing if you have flashing. This will never leak ever but...... most roofer will screw up the most basic job so there's that as well.

[@asm101]

Building science explained in a way i can understand

[@nottjohn9418]

Why am I watching this if I don't know what a parapet wall is? Boredom.

[@TheGMBJ]

Is there a cross section detail on this and detail of how the inner leaf is then fixed and secured? by brickie hasnt seen it done this way before and doesnt seem super keen!

[@dazosborn2469]

Good info Roger. It seems a dumb idea. I've always thought why would you want to try and create a swimming pool on your roof!

[@burwoodbuild]

Parapet walls... Trendy but sh*t! However I really do like your suggestion for solving cold bridging! Definitely could be useful in the future. 💯😀

[@somedude-lc5dy]

I wonder if you could use some kind of light weight fire-brick for the top portion since you're already above the roofing and it does not need to be structural. that way it's still masonry all the way up, but the higher R-value would prevent bridging. I also wonder if you could just bump out the upper 8-12 inches of the roof an inch or so to put some foam board in there. maybe hide it with some big crown molding

[@DICEGEORGE]

And leaves get stuck up on the roof and clog the drains which leads to more damp problems

[@mariotommadich4685]

Would it not be easier to just add some external insulation to the roof-facing side of the parapet to draw the dew point up and out of the heated part of the wall?

[@francisau8003]

Roger, thank you so so much, you have given me a lot of inspiration and key things i need to take into account when designing a parapet wall for my Masters in Building Surveying coursework!!