Warm roof box gutter detailing

The customer was complaining that he had draughts inside the room below this warm roof. When we stripped the old roof, it was found that the front soffit was venting directly under the roof insulation.
No effort had been put into insulation around the box gutter, the wind just circulated into the roof void. We corrected this by putting a vertical barrier of insulation and made the roof void completely airtight.

[@Joey-Cameltoe]

You do some great videos Steve! Really useful for us Surveyors. Cheers!

[@SteveRoofer]

Glad you like them!

[@alanwilliams4835]

Just a great video loving you work

[@Best-roofersCoUk]

Good to see you posting again

[@notsosimple23]

Now that’s magic @ 2:38 😱

[@Messimagician83]

Steve Hare haha I had to watch it twice, the first time I thought my eyes were playing tricks.

[@SteveRoofer]

When I was editing it I had to watch it two or three times, the video has only been up for 3 or 4 hours and you spotted it. I'm assuming others will and I'm going to be inundated with questions about my magic powers.

[@rickbaguley7997]

Hi Steve, Super video I am building an extension on my own home with a warm flat roof surrounded by parapet walls with a roof lantern. it is approximately 4m front to back and 10 m wide. There is a 1m step on the building side reducing the depth to about 3 meters 4m from one side. I was intending to have a 1/60 ish fall front to back with a box gutter along the 10 m length by the long parapet wall running down to a scupper drain at one side. I understand that my insulation must be 150mm thick. Could I use 100mm insulation with 50mm insulation on top leaving out the 50mm insulation to create the box gutter or would I need to put more insulation underneath between the joists. I am mindful that if insulation was required between the joists then this would be below the vapor barrier.. Kind Regards and thanks in advance , Rick

[@SteveRoofer]

Okay yes you can do what you're saying yes you can put some underneath it in the box gutter if you want to however it's okay not to he will have a slight cold area in that area but 100 mm of insulation is fantastic so you won't have a problem with interstitial condensation at that point if you do put some under it and that is under the vapour barrier again and not a problem because there is so much insulation above you won't get into stitch or condensation in that area.

[@rickbaguley7997]

@@SteveRoofer Super Steve, thanks very much :)

[@rorys1982]

Hi Steve. Great videos. I was wondering. How did you deal with airtightness for the lower insulation, inder the first osb deck? Did you foam on top of it then place the tg board onto this?

[@SteveRoofer]

we basically stepped the roof and made shore the AVCL (air vapour control layer) was continues and the insulation was continues and also overlapped at the step to stop thermal bridging

[@carlreed1000]

Great informative videos. How many fixings per stirling board do you recommend?. From this video it looks about every 500-600mm. Is that about right?. Thanks in advance. Oh and where do you get them from

[@SteveRoofer]

every 40 around the edges to stop wind uplift then every 600

[@kieranhiggins2410]

What thickness was the box gutter insulation?

[@MrX-mg1zx]

How did you secure the timber at the end of the insulation (thsts the same thickness as the insulation) where the secret gutter is. If its standing up on its edge, I can't see how you secured it.

[@SteveRoofer]

Long Screws

[@omstygomsty]

Hi Steve, Great video and so well explained. What size box gutter do you recommend and what is the fall on the flat roof to the box gutter and the fall on the box gutter to the hopper and down pipe?

[@haroon420]

steve, as a follow up to the above question, does the box gutter need to be that wide? Can it be narrower? We're looking to get a flat roof laid on our extension in a few months time and having seen the box gutter, I think it is a good solution to hide the gutter pipe and have a nice clean look at the front.

[@giotto4321]

​@@haroon420 The gutter width is almost always driven by the diameter of the flange on the outlet that forms the drainage point. For an outlet on a vertical outlet 100mm diam. downpipe this is often around 300mm and that sits fixed to the bottom of the gutter. Having the lining material properly dressed over the outlet's fixing flange and into the outlet itself means you need that sort of width of overlap. You don't want to skimp on drainage sizes, failure can be quite messy internally and distressing for the owner/occupier!

[@b24fitfitnessnutrition43]

Hi Steve, I’m hoping you can help me. If I’m using a warm roof on our diy garden room, do I put the 100mm pir right to the edge of the first deck? Do I need anything on the outside of that insulation to keep it in place or do I just using the fixings you suggest in another video? Tia Barney

[@zalkhirsan9481]

Waww no vapour barrier !!

[@sjiroofingandmaintenancese2494]

Would be a nice job in single ply

[@gdfggggg]

Ahh, the wonder that is expanding foam I see..