A fair point, but we only end up with a 6x2 at the point that it meets the RSJ, which is more than enough for strength...The 9x2 was specified for the depth it allows for the insulation and air gap, rather than the strength it provides.
It depends on the type of roof. In a cold roof you don't need a vapour barrier because it's fully ventilated, and inside the room you generally have a layer of 30-40mm PIR which acts as a vapour barrier in the room. On a warm roof system you absolutely need to have a vapour barrier in place on top of the OSB, before you lay the PIR insulation.
Very nice work and informative video! Can I ask how much ceiling height you managed to get in this conversion and what finished ceiling height is considered good for a loft bedroom? Thank you.
Thanks mate, glad it's been helpful! The finished ceiling height is around 2.3-2.4m which is great - Very comfortable. I think 2 meters or less starts to feel cramped and a bit too low, but it is personal preference on that.
@@OfficeBoyBuilder thank you very much for your quick response, much appreciated. Our loft conversion build is going on and the height from the chipboard floor to the dormer joist is 2.32m so I think after putting the laminate flooring and insulation and plasterboard on we’ll be left with around 2.3m. Hence wanted to check how it feels as our ground floor ceiling height is 2.7m.
4 min 10 secs... is the apex timber where the front rafters join bolted to the steel or just installed to both ends? Will be looking forward to hearing from you. Thanks
We didn't bolt anything to the steels on the outside or where rafters joined. We bolted the steel internally, where the timber posts met the steel. Hope that helps!
Good details of the cold roof deck, would you say by putting the batons across on top of the joist for ventilation is not as strong for the osb board if they were screwed directly on to the joists. I think there is more work for cold deck and many ppl are missing that detail about leaving the gap at the top of joists for circulation.
I am a fan of warm deck but I'm thinking of doing my loft dormer conv and think that there's not enough height for warm deck roof. Looks like it will be 2.38m from bottom of dormer to top of ridge.
@@harrysingh1145 I think you'd struggle to get a warm deck in there to be honest mate... you'd be better with a cold deck and enjoying more head height after the pain and effort of getting it all done well.
@@harrysingh1145 remember that the regs say you need 50mm air gap minimum, unless you're using kingspan or celotex etc. Which have been rated down to 25mm air gap. It's only a small amount, but it makes a difference when all added up.
@@OfficeBoyBuilder thanks, you mean pir foam insulation rather than normal loft insulation. Iko entherm pir insulation thats wat i normally use. Good to know
Sure do, send me an email (officeboybuilder@gmail.com) and we can be in touch. We work in South East London, so if you're in that general area we may be able to help 💪👍
Yes. Our structural engineer specified 4 timber posts on each side, and these were further supported by 1 meter worth of noggins on each side of the timber posts.
@@OfficeBoyBuilder I can't get my head around that. Wasn't it 300kg of steel (from the prev vid) and all the weight of roof and dormer...all supported by 4 timbers each end.. Just feels wrong..
No it isn't...go to 42 seconds, and you'll see that the top point of the sloping roof is higher than the flat roof. The building inspector wouldn't have signed off the work if we hadn't stuck to the building regs and the specification set by the structural engineer.
thank you!
What's the point in putting in a 9x2 ceiling joist and then cutting 3 " or more off it to go into the channel of the rsj, you only have a 6x 2 now.
A fair point, but we only end up with a 6x2 at the point that it meets the RSJ, which is more than enough for strength...The 9x2 was specified for the depth it allows for the insulation and air gap, rather than the strength it provides.
Because the maximum bending moment is in the middle of the joist and the max shear factor at the bearing ends. The extra depth matters.
Does anyone know how the 9 inch beams fix ti the steel?
Does it make any sense to place vapour barrier anywhere on the flat roof? Beneath OSB perhaps?
It depends on the type of roof. In a cold roof you don't need a vapour barrier because it's fully ventilated, and inside the room you generally have a layer of 30-40mm PIR which acts as a vapour barrier in the room. On a warm roof system you absolutely need to have a vapour barrier in place on top of the OSB, before you lay the PIR insulation.
Very nice work and informative video! Can I ask how much ceiling height you managed to get in this conversion and what finished ceiling height is considered good for a loft bedroom? Thank you.
Thanks mate, glad it's been helpful!
The finished ceiling height is around 2.3-2.4m which is great - Very comfortable. I think 2 meters or less starts to feel cramped and a bit too low, but it is personal preference on that.
@@OfficeBoyBuilder thank you very much for your quick response, much appreciated. Our loft conversion build is going on and the height from the chipboard floor to the dormer joist is 2.32m so I think after putting the laminate flooring and insulation and plasterboard on we’ll be left with around 2.3m. Hence wanted to check how it feels as our ground floor ceiling height is 2.7m.
4 min 10 secs... is the apex timber where the front rafters join bolted to the steel or just installed to both ends?
Will be looking forward to hearing from you.
Thanks
We didn't bolt anything to the steels on the outside or where rafters joined. We bolted the steel internally, where the timber posts met the steel. Hope that helps!
@@OfficeBoyBuilder Thanks for the clarification
Good details of the cold roof deck, would you say by putting the batons across on top of the joist for ventilation is not as strong for the osb board if they were screwed directly on to the joists. I think there is more work for cold deck and many ppl are missing that detail about leaving the gap at the top of joists for circulation.
I am a fan of warm deck but I'm thinking of doing my loft dormer conv and think that there's not enough height for warm deck roof. Looks like it will be 2.38m from bottom of dormer to top of ridge.
@@harrysingh1145 I think you'd struggle to get a warm deck in there to be honest mate... you'd be better with a cold deck and enjoying more head height after the pain and effort of getting it all done well.
Yes i think it will be cold deck just need to make sure i get all the details before i do it on the air circulation
@@harrysingh1145 remember that the regs say you need 50mm air gap minimum, unless you're using kingspan or celotex etc. Which have been rated down to 25mm air gap. It's only a small amount, but it makes a difference when all added up.
@@OfficeBoyBuilder thanks, you mean pir foam insulation rather than normal loft insulation. Iko entherm pir insulation thats wat i normally use. Good to know
At 1:39
Dangerous stuff shooting nails above someone’s head like that.
A slip or something could cause horrific injuries
How much would it cost to get the dormer rooflike this
The basic structure probably costs around £35-45K these days.
Love your channel!I would love to know how much it cost you to have the shell built?!
Keep up the good work 👏
Cheers! It was £35k including VAT 👍 Timber prices have gone up a lot since then sadly
@@OfficeBoyBuilder thanks once again for the swift reply.
I really appreciate it 🙏
How much does it cost to make a dormer both side of cape house, also adding garage conversation,
Almost impossible to say without taking a look and seeing what the space is like/how big the place is...!
Have you got a contact for your builder? Many thanks
Sure do, send me an email (officeboybuilder@gmail.com) and we can be in touch. We work in South East London, so if you're in that general area we may be able to help 💪👍
@@OfficeBoyBuilder Smashing, I'll drop you an email today.
Is that steel just sat on timber posts?
Yes. Our structural engineer specified 4 timber posts on each side, and these were further supported by 1 meter worth of noggins on each side of the timber posts.
Jason Lloyd g
@@OfficeBoyBuilder Good work.
@@OfficeBoyBuilder I can't get my head around that. Wasn't it 300kg of steel (from the prev vid) and all the weight of roof and dormer...all supported by 4 timbers each end..
Just feels wrong..
It's unclear to me how you are going to arrange ventilation and prevent water ingress at the ridge 🤔
We have used a vented dry ridge, and then mushroom vents in the flat roof and a vented sofit at the front of the house 👍
This dormer was built incorrectly as the flat roof is higher than the tiled front roof lol 😂
No it isn't...go to 42 seconds, and you'll see that the top point of the sloping roof is higher than the flat roof. The building inspector wouldn't have signed off the work if we hadn't stuck to the building regs and the specification set by the structural engineer.