A Deeper Dive Behind Parapet Walls 

Fantastic explanation! Thanks Swwils!

I knew when I said that it would be hard to get it in under 2 minutes. I should have shut up.

"This kitchen and flooring reno should only take a couple of weeks...", said I to my client a month ago 😂. Might be done end of next week.

Most modern weep vents also allow some cavity ventilation. They also can prevent pressure differentials so moisture is not forced into the cavity.

Your grandchildren will be saying the opposite as they try to deal with global warming !!

@@thetessellater9163 maybe! maybe not! Heard of the cooling cycle, we're heading for another ice age. Anyway l,d be more worried about stray asteroids coming from deep space, on the bright side we're won't know what hut us. 🤯👍🎯

@@MikeAG333 🤔🤣🤣🤣

The only problem is that the 4 inch brick wall is not that stable.

Good point

the membrane under the coping SHOULD show a half inch , i know it looks ugly but it WORKS !!

@@pauldavies5655 - where is the attachment of the coping ? With the membrane right under the coping, you may be risking detachment in high winds.

@@thetessellater9163 you can do it easily with DPC --- it will take a wind of over 120 miles an hour to dislodge a coping done properly. i know of coping stones in britain at the end of 4 storey roofs ( we call em FINIANS ) which have survived a 120 years untill the main roof covering needed changing ! also look at the shape of each coping stone and adjust it to the wind conditions in that area --- common sense ! remember , make it secure -- make it WORK , NOT make it look pretty !

The principal is to stop airborne moisture getting into the roof so the vapour barrier needs to lap up the side of the roof to the top edge.

@Skill Builder how can it if you have the top deck on top of the insulation and then build a stud wall on top deck if the insulation is going right though to stop the coldthen how do I get the vapour barrier back up the outside wall do you screw the stud wall on top of the vapour barrier? Bit confused sorry

No OSB 3 is great. A lot of GRP suppliers insist on it.

Good idea

Could be useful for 'trickle venting' the house though. Chimney breasts are also used for lateral restraint on a long wall, if you and your neighbours both remove them, there could be issues with stability.

Coming soon!

I don't know jack about plumbing, I'm only thumbing up your post in the hopes that someone else with knowledge might notice it and give u sound advice. Best of luck Edit. Have you jumped onto an online plumbing forum?

I was just thinking the same thing. It doesn't seem to be very well known about as a product, the jury's out in that one, but it would be nice to hear from someone who's actually used it.

Upstand studs are quite well performing insulator. You don't put insulation below studs. You put it between. If you make timber upstand it is way better than any concrete block or brick. Thermalite block is a different storry. Actually would be easy to find u values for timber and thermalite to compare. But premise of video with assumption of timber ceilimg would be that where timber beams rest on the internal wall, the wall continues with insulation layer, not block. Then you have a plate on top of insulation, dwarf studs on top of plate, then another plate just below caping... Ceiling noggings 1- 3 inches away from wall. Osb board from top acting like a shield + noggings just next to the wall along with the dwarf wall bottom plate should prevent any warping on 4 inch support area of timber warm roof joists. Previous video postulated moving temperature stress point (sorry not an engineer - point where cold crawling through material from top meets warm temperature crawling from the living space from the bottom) be moved from inside the living space somehwere inside the wall under the ceiling to somewhere inside fhe ceiling level, _inside the bearing part of the roof joists_. I would guess that with an extra bit of the insulation marked on the above video as upstand, this temperature would move into the level of actual paraphet wall's upstand's timber plate (not marked on this video) and be as negligible as possible, but hey, Roger is a God of 'Why won't we consider *thiz* today' and i am sure there are dozens of people who would be inspired to get some science done and tell us how those things work. Building is art and forgotten lore. Art is chaos. Forgotten lore is forgotten. We all have passion and try for the best but we are still shaken by paradigm shift that took place somewhere in the second half of XX century. We just try for the best.

@@kerel995 if you just have the stud work on top of the block work you’ll probably be better off going with thermolite block instead. It would be nice to see some numbers/evidence

@@mooney0086 previous Roger's video said: Insulation inside warm roof goes over concrete wall that ends at the bottom of roof joists. Then in between bearing part of joists you have full insulation. Upstand is on top of roof joists. Regarding numbers, this is like a little nerdy math excercise I would love to read calculations for timber bridging too ;)

@@kerel995 I’d imagine building control would want SE calculations for adding coping stones on to a timber frame too. More expense 🤦🏻

@@mooney0086 absolutely crossed my mind. I like the way your brainz work ;)

The inner leaf of the gable is not exposed to the elements, so warmer, but still must lose some heat to the outside. Maybe not enough cold bridging to form condensation, and if so, the ventilation in the loft should take care of it.

@@thetessellater9163 silly question, would the orientation of the building not affect the inner leaf of a gable? I.e, driving wind/rain?

Our gable is north facing, so it’s a cold wall anyway, but my point really was the temperature in the loft is very low above the insulation, and the inner leaf of the gable bypasses the insulation, so it must soak heat out of the house. Wasn’t particularly suggesting a condensation issue, just bridging.

Insulation is meant to be carried up at least 200mm up the cavity in the gable. The roof is also meant to have perimeter insulation - this is often missed on cold roof constructions where there will be a gap where no insulation is between the gable and the first ceiling joist before the horizontal insulation of the attic, usually exposing the room belows ceiling plasterboard corner to cold attic air.

The Party Wall agreement should cover all aspects of the groundwork too. There is no 'right to light' as some people assume. They should have no right to even put foundations on your land, so make sure this is stipulated. You can use your own Party Wall Surveyor, to look after your interests, for which your neighbours must meet the cost of.

You are wrong. OSB is specified over ply because ply delaminates.

I hate Osb. Yuk.

That would be a 'cold roof' which is less efficient.

Hi Richard Yes please it would be good to see. We have a couple of variations from viewers so it would be great to see them side by side.

That would be great to see. Perhaps Roger could show them in another video? I'm always keen to learn new insulating and flashing details, even if my work here in Canada is much simpler. Cheers!

@@SkillBuilder not sure I can upload PDF images on here would it be best to email you?

@@richardphillips7581 Can you email to me please?

@@brianstorm4806 yes but can’t seem to find your email address

I was thinking that but I think as it’s a cavity wall you still need to tie the top part of the outer brick skin to the inner skin, and I assume you can’t fix steel wall ties to PIR

@@charlespudge3371 I think that when the parapet wall isn't any higher than a foot the single outer leaf can do well without the ties, but when you have a 4ft high parapet wall to act as a barrier around a roof terrace this is a different matter. In my case I'm looking to build parapet walls which are more like upstands for the roof but with a metal coping over it to look like a proper parapet wall from the outside without having barge boards or such.

Alao, would insulating the inside edge of the warm roof solve it? There’s plenty of space between the rafters…

I have never layed a block on screed in my opinion the drawing is wrong ...where is it from Rodger...?(Brickie 33yrs exp)

@@stuartnicklin4101 seen the diagram in the nhbc standards - flat roofing

... "need to up my skills and knowledge"... Don't we all my friend! Me too!!!

Thank you, I just need to calm down and learn how to draw

I am with you on that Paul.

@@MikeAG333 - my 'architect' submitted my plans to Building Control and had 17 revisions to make - not all architects are equally knowledgeable - he learnt from me too over the need for a short section of corridor for fire regs.

@@MikeAG333you may listen but it s a shame other architects do NOT !! we are at ground ZERO all the time , you boys sit in offices a lot of the time -- work it out mate ! ps -- and yes planners DO have an input because they allways want things to look pretty NOT how they perform in conditions they know very little of !

@@MikeAG333 well i actually AGRRE with you on that ,BC and town planners are in bloody world of their own sometimes. they do not ever take the blame if their conditions are a LOAD OF SHITE !! lol they just work for the government in most case s and their job is protected anyway ! it is the builders name which becomes mud due to very poor plans and conditions we are subjected to .

@@MikeAG333 lol, well there you are then as i have worked for "english heriitage" " the national trust" CADW , the army and the government . they all have listed buildings ! PS--- if any council has a certain VISAGE for the area due to a councilors preference then it will be followed through regardless of any architect or builder my friend !