Warm roofs, the biggest mistake I see when doing a roof inspection.

Alway phone or email if you need help or advise
Steven Dickinson
London Flat Roofing
07802300099

Nobody tucks in their warm roofs!
What do I mean?
If you bought a new quilt for your bed and you laid down under it but didn't tuck it in around the edges, you would get cold. Same for when you're doing a warm roof, you have to extend the insulation down to the next thermal element of the building. I call this "tucking in your warm roof"
The reason nobody tucks in their warm roofs is because of the cost of doing so. You not only have the labour of doing it, but you also may have to remove the fascia boards or gutter boards to get access to the area that needs tucking in. Thermally tucking in your new warm roof makes all the difference. It not only continues the thermal performance of the new water roof down to the next thermal element of the roof, but it also makes the roof airtight. I have been to many new warm roofs when carrying our roof inspections for customers and they complain about how cold it is in their house even though they have had a new warm roof. When I'm doing a roof survey, I often take out light fittings and feel a draft straight away. I know that the roof is not airtight, and normally, it's because they haven't put the insulation between the joists at the ends only. Putting insulation between the joists further into the room on a warm roof is totally another thing, and I covered this in another video; you should not have to do that if you have the core thickness on the new warm roof. I would suggest that tucking in a new warm roof on a loft conversion is the most complicated, more complicated than a rear extension flat roof. With a flat roof over a loft conversion, you have to tuck in the insulation at both ends, whereas on a rear extension, you normally only have to do the tree edges, and access is a lot easier.

Steven Dickinson
London Flat Roofing
07802300099

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[mikebarry]

As a former Building Control surveyor this was such a common issue, both on new extensions, replacement flat roofs, and even on large new housing developments. On domestic work I would probably say this simple point was missed getting on for 50% of the jobs that I saw at this stage. The issue is that many builders build the walls as they always did with ventilated cold roofs, stopping the walls at plate height. This also applied to the walls parallel to the joists leaving an uninsulated void between the top of the wall, the deck and the joists either side, with only at best a 25mm gap to get the insulation into the void when the issue was pointed out. It really isnt good enough to just fill up the space with quilt as this can create condensation issues, it really needs to be PIR as Steve shows here foamed into place. Another important factor when upgrading a ventilated cold roof to a warm roof is that you need to remove all the old roof insulation from between the existing joists, leaving it in place, particularly if there is a good thickness, means that the vapour barrier under the new insulation will not be at room temperature and can cause condensation problems that the warm roof was designed to overcome.

[DannyDangerOz]

We bought a house and the previous owner was really proud of the money he'd spent on insulation. We'd have bought the house regardless, but after we bought it I realised he'd wasted his money because the people who had installed it had left big gaps which allowed airflow.

We're slowly working on it ourselves now, but this video was great as it showed me I was right about the issues, and my approach has been more or less correct, too. Thank you!

[jaki]

We had new extension done few years ago using the warm room method and they didn’t fill the gap with insulation between joists, our new extension was absolutely freezing in the winter. I showed the builder your video on thermal bridging and they took the fascia board down and corrected it and now it feels warm and cozy. Thanks for these educational videos

[andyjm]

Thanks Steve for taking the time to put these vids out. They are invaluable to all homeowners.

[aarongeorge]

Wish I'd seen your advice years back. Educating people on how to do it right no matter the cost is always worth it. But everyone wants it done cheap and fast.

[jonwilmot]

Dear steve et Al. I have just pulled 1500 kg of lead off my annexe which after 20 years was like a burst sofa. It was laid on a warm roof done badly with no vapour barrier. I have stripped it and used Allutrix then put Res Tech flexible fibreglass over the new deck. Vapour barrier and thermal bridging control is critical when working on modern roof systems. Thanks for a very good video.

[dragonfitter]

If you completely seal up roofs like that the timber will rot out double quick . Sealing everything up causes all sorts of problems and we leave air gaps on purpose you will cause mould, condensation and damp .

[dannymurphy]

Thanks Steve, great vid as always. I think what you have to remember is warm air is attracted to cold air, so if you have these tight gaps the air fairly whistles out. It would be interesting to compare say 18mm ply totally sealed at the edges with insulation with gaps in that area.

[Robert-tsef]

I thought that you had to leave a space where the ceiling insulation meets the soffit for ventilation of air to be able to get in and stop roof condensation?

[johnhaydon]

When we built our lofty on a 3 bed semi we spent ages and a lot of money insulating the roof and walls and getting obsesive about draught proofing. In the last three years since we have never turned on the reads up here, the loft stays very cosy all winter with just the heat leaking up from downstairs. To be fair though you do need a forward looking customer to agree the extra costs involved in getting it right, done well though a few years of reduced heating bills and you have paid for it. Good video, thank you.

[BigA]

Did I read somewhere that you been a flow of air in the foot area to prevent moisture build up and mold - which is why soffit boards have holes in them to allow for breathing?

[TheRonskiman]

Years ago we had a kitchen done with a warm roof, the builders did a horrendous job, large gaps, they blocked roof vents because they couldn't be bothered to trim them down, it was so bad I took it down and redid it. Reading a few comments here, it seems that most of the mistakes are down to builders, the so called professionals! Hence why I do most things myself, if you want something doing correctly do it yourself.

[GleneaglesDriveVilla]

Thanks for the info. Had a flat roof extension done last year and it saddens me that i know for a fact this tucking in was NOT done. So this summer it’s fascia’s off and do it properly … Myself 😢

[reubengregory]

Hi. Interesting video. But perhaps you could do another to clear up some confusion. Especially for owner of older houses that require ventilation in their rooves to stop condensation. I have tried this method with my new roof and quickly discovered that the roof needed air movement yet I still would like to be able to some how seal out the cold air from out side getting into the inner space on the other side of the insulation. How do we do that?

[petesshed]

Very good video Steve. Thanks for the info. I always thought (or think I was told when I did my Carpentry & Joinery course between '94-'97) that you had to leave a gap between floorboards for air to circulate. I guess this has now been superseded in today's world? Thanks once again and ATB

[trueriver]

I made this mistake back in the eighties when i insulated the roof of a house i owned at the time. I didn't do this.

In fairness I did get some noticeable benefit from the roof insulation. No doubt it would have been even better had i done it properly.

I'm wondering now if any owner since I sold that house has noticed the problem😮

[c]

Im a builder and youre stating the obvious( to me). I always fit 2 x 100 mm layers between the joists at that location. Blindingly obvious.

[nicholasmitchell]

Another way to look at it is, imagine if the celotex board was seen?

You would make sure the scribing of the board is as neat as cutting in emultion paint between walls and ceilings.

The outcome is an optimal thermal barrier, of such efficiency that your investment would be returned before the end of the 1st cold season.

In other words, the time between your thermostat kicking in your heating system would be much much longer.

We do this automatically by ensuring the front door is closed immediately after stepping in.

Or we build a small porch around the front door, that also functions as a thermal barrier, alongside somewhere to put wet coats and shoes.

[jack_irl]

Thanks Steve Roofer! I'm looking to build a workshop and this will be excellent!

[WhiteManInAVan]

I really like my builder, so I'm hoping he's done this on my new extension. I'll be checking when the wind picks up.