I started to specialise in roofing and then in flat roofing. I've tested more than 15 different liquid roofing systems, and worked with vinyl roofing and EPDM rubber. In recent years I set up London Roof Surveys, mainly because as I'm getting older and wiser I tend to do more roof surveys. COVID hit, I lost one of my main workmen, so I had to reduce my roofing teams. One of the more positive knock-on effects of COVID was that my son-in-law was made redundant (COVID) from his job as an aircraft engineer, and he came to work with me. Now, two years on, he is starting to take over the roofing side of the business. Coming from a background in the aviation industry, where strict rules apply to supply and maintenance, he is amazed at how lax the building industry is. It is a pleasure to have someone working with me who thinks and cares about what he is doing, together with having foresight and understanding with regard to the consequences of our work on roofs for the years to come.
A correction to a statement. Building Science Corp has proven that condensation will only occur when moisture-latent air hits the FIRST cold surface (that has a low enough temperature to produce condensation, ie a BTU transfer)... in rigid insulation, you made a statement using your fingers that it would condensate somewhere within the upper portion of the insulation itself, it simply does not do that, the math equation says it will (which you referenced) along with the computer models, but through extensive testing, it does not. Water "vapor" needs a cold-condensing surface. The rest of your statements are correct. The hard part to deal with is the water vapor and controlling it, since it is very difficult to create a perfect seal. You can create a ventless fully insulated roof but you really need to know what you are doing, Canada learned its lesson on SIP panels years ago, and Building Science Corp solved the issue. Building Science Corp has hundreds of white papers on this issue. GOOD READ for those who do this for a living. Another note is that this is all dependent on the climate zone. Warm moist and Warm dry climates perform differently.
What a great video explained really clear thank you for your time . I am doing an extension 3mtr x 5mtr block cavity I like the idea of the warm roof but I will be installing it to butt up under eves of single storey , that insulation being 150 plus joists , yet to be configured , that could be tight , I'll have to do slot of measuring may end up with a lower ceiling than existing building , would I be right in thinking this. ?
Great video! I’ve a question tho. If you’ve a warm roof like what you showed in min 3:45, and there is then condensation somewhere in the middle of the insulation (where the two temperatures meet), isn’t that a problem for fungus ? Because the condensation is stuck in the insulation?
I've been getting really confused with all the barriers, which order, air gaps etc but these have helped better than most all others combined... shame they only came up after hours of others. The cold roof explained is what I really needed. One thing I don't get is the real difference between a vapour varrier and dpm if the goal is stop moisture from inside penetrate the insuoation and condense inside it then if dpm stops more then aren't they always better?... or is the vapour barrier the outside where air gap is and if so is it really needed if its vented?
I have to say Steve, I have been watching your videos for years and love your enthusiasm and practical fact based explanation of the "right" way to put a flat roof together, I would love to have a coffee with your sometime.
The "if" part of a two layer construction (rather than single layer) is whether sufficient moisture could accumulate at the layer join for it to actually condense out and then propagate the potential mould/rot. The solid PIR has nowhere for there to be that condensable moisture (compare with mineral wool etc). It's a long slow game (decade of life) to ensure that the moisture doesn't have opportunities to ruin everything. So many things to consider!
Hi Steve, I sincerely appreciate your videos. You specialize in a crucial area of the roofing industry by addressing moisture-related issues. There's a significant need for education in this aspect of our field.
i hate glass fiber roofs just use epdm easy super strong essay to joint never had a problem with them. glass fiber way to many variables Keep up the good work Steve..
@@redline589 Yeh I've installed both types on my property (both DIY) & think both have their pros & cons IMO. For my small roof with lots of complicated shapes like several kerbs for roof windows etc GRP was a better option in my own opinion. I used EPDM for my other roof which is a simple large flat roof with only 2 flat/low profile windows on it.
Can you do a video about insulating solid walls (i.e. no cavity) and the issues around interstitial condensation, air gap or not, breathable insulation or not etc. There are millions of homes in the UK that have solid walls and would be good to hear from you on the subject if you can speak to it?
I could be wrong but I think I can spot some black plastic sheeting just say sticking up out of the 1st insulation layer at the corner after the window & the top right corner which may have been used as the vapour control layer. I'm not saying that would be correct, just pointing out what I think I can see.
You could be right; however, plastic is the wrong material to use on a warm roof. Additionally, plastic Air Vapour Control Layers (AVCL) are typically green. Black is normally the color used for Damp Proof Course (DPC) or Damp Proof Membranes (DPM), all of which do not use virgin plastic and therefore do not offer the correct vapor resistance.
I would guess that you would say the existing felt is a bad AVCL when converting an uninsulated roof to a warm roof. My bungalow had a secong floor with dormers added and flat roof extension 18 years ago. Not a scrap of insulation anywhere. Expensive to heat in the winter and an oven in the summer. At least th electrician was good out i would be much more concerned.
no the existing roof can make a very good air vapour controller because the problem is tucking the roofing around the edge which was the subject of my last video. You've gotta make sure that you tuck it in around the edge. Bring the thermal element of the insulation that's gonna go over the top of the roof down to the next thermal element which is the wall this is so often missed and therefore realistically you're losing 7080% of the performance of the roof by not doing it
As well over overlapping joints reducing leakage, other advantages of multiple layers: less bowing (especially after cutting) and easier to cut, especially around corners and protrusions.
I am thinking of putting solar on my 3 bedroom semi detached simple pitched roof, the roof is the original build and I was wondering would it be wise to change the roof first or not bother as its still functioning - I appreciate this is a bit of a difficult question without seeing the roof (about 50 years old) ut would appreciate your thoughts on the matter thanks 👍🏻
It certainly has to be a warm roof when it’s located in Scotland, do you ever work up that way or are you just looking for work in London? I can possibly put you in touch with a roofer that also specialises in water damage etc that you could liase with he lives up that way.
Those plastic polypropylene slates aren't good. They are amazing to use, all the same thickness, look great, lightweight. So quick and easy to use. They tick loads of boxes until you see them 2/ 3 years after you've put them on. They fade terribly like all plastic materials. The wrong client will pursue you if they are very particular
I installed 142 mm alufoil-faced insulation for my workshop build. The external sheeting was already completed, so I had real problems getting a precisely cut sheet into the stud gaps. Effectively, the sheet was compressing air. I found the most effective way to get a good seal was to cut the sheet exactly 10 mm too small, insert the sheet, then fill the gap with foam, starting from the back of the space. Of course, a workshop doesn’t have the insulation and damp requirements of a house, but I wonder wonder if my solution would be acceptable for habitable spaces. Final point, I bought the Festool specialist insulation saw. Used with their track it enabled extremely accurate and square cuts in the insulation. Disgracefully expensive though!
Hi - I’m just designing my warm roof solution for an existing flat roof, thanks for your videos they are really informative. I intend to use Alutrix 600 but wanted to ask about it securing to a concrete slab roof - would you use any primer or additional adhesive Also what mechanical fittings would you recommend for securing the new insulation and osb to the concrete slab Thanks in advance
hi , thanks for video ! planning my new roof , same cold roof , joists hanging on the wall with hangers , got the walls from sides .. need ventilation! how is better to do .. go battens along the joists then across the joists ? need 2 layers of battens or one ?! thank you
My roofing company in Utah, USA couldn't find anything decent on the market so we've begun using perforated metal z-bar and a custom bent-counter flashing which cleats into the z-bar. Very cost-effective, readily available materials without too much fabrication needed, and it's all metal, holds together very nicely, feels solid, and flashes into headwall same as any other counter flashing.
Hello Steve, I’m a carpenter new to the UK from NZ where our insulation regs are a lot different. I’m doing my first build here for a client, and the original plan was a pitched roof extension with cold roof insulation. The pitched ceiling has now changed to a flat ceiling but still a pitched roof. Am I better off insulating the flat ceiling, or the pitched roof?
Thanks for the video. We have a very similar bacony that recently was painted with fiber glass and keeps cracking. Do you still recommend Hydrostop EU AH-25 6 years on?
Hi, how many screws per sheet of insulation would you use? I'm doing a flat roof soon with Resitrix, 130mm insulation and Alutrix. The architect doesn't want another layer of plywood on top on the insulation before the Resitrix. Thank you.
Hey Steve Roofer. Can I ask you a question here? I've built a summerhouse in the garden and haven't thought about venting anything until I recently saw your videos. It's framed with 100x50mm pressure treated timber. Whilst I could vent the roof without too much hassle venting the wall cavities is going to be a challenge. The outside walls are UPVC cladding over a polythene sheet and the roof is epdm. So there's not much scope for water to move out if it gets trapped in the walls. It's a dilema and i just asked ChatGPT what he thought and he suggested using closed cell spray foam insulation which means i don't need to worry about venting anything as the foam is a vapour barrier and completely impermiable and there will be no gaps for air or moisture to move across. What say you?
All i’d add is the first one, he’s making a PIR sandwich with the 25mm on top. Should be the other way around as the dew point is pushed further out so any gaps in the expanding foam will be somewhere for interstitial condensation to form. Small risk and low volumes but easily eliminated if reversed.
