To do a warm roof he’d need all the build up (base deck, bitumen foil vapour barrier, insulation & roof covering) ABOVE the joists, so he may not have the height to do that - ie. he might be restricted by window cills on the abutment wall or parapet height. If it’s not possible to do a warm roof then, as you say, he’s got to build the best cold roof he can between the joists. If he’s struggling to get enough ventilation draw across the 50mm air space on top of the insulation (continuous slot vent gaps at the eaves & apex are the best), the other thing he could do would be to beef up the vapour barrier to a fully sealed version. Vapour barriers need to be on the warm side of the insulation so if he has got to fit a layer of insulation below the joists, he could then fit a thin board (hardboard or 4mm ply) below this as a key for the vapour barrier. He could then use a high quality laminated polythene product fitted with spray adhesive to avoid nail or staple punctures. He could then fit some 50mm mastic tape across the vapour barrier onto which he could screw 25x50mm battens up into the joists, with the mastic tape sealing the screw punctures. He could then run wiring for lighting in this 25mm void safe in the knowledge that his vapour barrier will not be punctured, before finally fitting plasterboard to the battens. With this construction it would be possible to achieve a vapour barrier with an Sd value of something like 100m which would effectively ensure that little or no vapour could rise up through the insulation in the first place.
I'm interested to know if your statement about cold roofs not working anymore due to insulation levels is based on your experience remedying flat roof issues or from some specific research? If it is from research please could you share the source as I would really like to read it. Thanks
Hi Steve, I do like your videos as they are full of well explained knowledge. I have a one question for which I cannot find an answer (just some discussions). I have a gable roof with cold attic. THe roof is covered by vapor-permeable membrane and ceramic roof tiles. Under that there's a mineral wool with vapor barrier. Should I warm up the attic by putting mineral wool between rafters or it's better to keep it like that? If so, should I also protect that wool with vapor barrier? What about the ventilation?
Hi iv recently had an extension full wrap around the builder has laid a cold deck roof but it stayed on our specifications that a warm deck roof was to be followed on the design. The cold deck only had vented soffits but no ventilation on the building line side and no building control will not sign this off due to it no meeting Reg’s and going off design. Could a warm deck be laid on top of the roof that is there now and will this pass regs.
Hi Steve, thanks for your videos, for a DIY'er these are so informative, so very grateful for them. I do have a question...🫣 Constructing a non inhabited shed. Walls are: (in to out) osb, air gap, reflective Vpr Barrier, 100mm 'wool', brthr Memb, air gap, cladding. Now, my question, the roof was going to be similar, (In to out) osb, air gap, reflective bubble insulation vpr barrier under joists, 200mm 'wool' btween joists, brthr membrane on top of joists, osb, epdm. I didnt intend to add any further ventilation to the roof. Cost is my main objective here as i cant afford the ideal PIR thickness etc and was hoping that spending a little xtra on reflective barriers combined with thicker cheap wool will get me closer to a better result. (Appreciate this isnt optimal, im not subject to any building control but still keeping shed low as possible) Will that be ok, as all moisture will be 'sealed' internally? I will be using extraction combined with dehumidifier as treating water for window cleaning buisness. P.S floor sealed and insulated Hopefully that all makes sense Nathan
thank you Steve, could you please give me a figure of thickness of PIR to use for a warm roof? we have a partly internal garage we are converting and have decided to go with a warm roof over the external part of the ceiling after watching many videos on your channel. many thanks
Hi Steve Just to let you know “Build it correctly” uses a still of you from one of your videos claiming these are the builders that don’t know what they are doing with flat roofs, Mr_A_ Builders have already challenged him as he does the same with them showing a still of their video and claiming they are installing flat roofs wrong I think he’s totally out of order
It would be great to see Steve create a new 2024 video of best practice for the make up of a warm flat roof. Address the issue being argued over at "build-better-things" where a top deck of 18mm osb typically seen added by most uk builders is bad?. The argument being raised is that this osb deck may still rot regardless of whether an EPDM, GRP or Torched on felt is used as the final roof covering. I'm not interested in whether the guy is right or wrong to have shown clips of other channels, but I am interested in well rounded expert advice from people such as Steve. PS: Many thanks to Steve for your technically informative videos.
@ There are plenty technical sites on RUclips with the new building regulations, and architectural drawing’s on the net explaining the warm roof makeup And they all state nothing wrong with the OSB being on top of the insulation Build better things has provided no evidence to back up what he “thinks” and that’s all it is
Hi iv recently had an extension full wrap around the builder has laid a cold deck roof but it stayed on our specifications that a warm deck roof was to be followed on the design. The cold deck only had vented soffits but no ventilation on the building line side and no building control will not sign this off due to it no meeting Reg’s and going off design. Could a warm deck be laid on top of the roof that is there now and will this pass regs.
Hi iv recently had an extension full wrap around the builder has laid a cold deck roof but it stayed on our specifications that a warm deck roof was to be followed on the design. The cold deck only had vented soffits but no ventilation on the building line side and no building control will not sign this off due to it no meeting Reg’s and going off design. Could a warm deck be laid on top of the roof that is there now and will this pass regs.
Hi iv recently had an extension full wrap around the builder has laid a cold deck roof but it stayed on our specifications that a warm deck roof was to be followed on the design. The cold deck only had vented soffits but no ventilation on the building line side and no building control will not sign this off due to it no meeting Reg’s and going off design. Could a warm deck be laid on top of the roof that is there now and will this pass regs.
To do a warm roof he’d need all the build up (base deck, bitumen foil vapour barrier, insulation & roof covering) ABOVE the joists, so he may not have the height to do that - ie. he might be restricted by window cills on the abutment wall or parapet height.
If it’s not possible to do a warm roof then, as you say, he’s got to build the best cold roof he can between the joists. If he’s struggling to get enough ventilation draw across the 50mm air space on top of the insulation (continuous slot vent gaps at the eaves & apex are the best), the other thing he could do would be to beef up the vapour barrier to a fully sealed version. Vapour barriers need to be on the warm side of the insulation so if he has got to fit a layer of insulation below the joists, he could then fit a thin board (hardboard or 4mm ply) below this as a key for the vapour barrier. He could then use a high quality laminated polythene product fitted with spray adhesive to avoid nail or staple punctures. He could then fit some 50mm mastic tape across the vapour barrier onto which he could screw 25x50mm battens up into the joists, with the mastic tape sealing the screw punctures. He could then run wiring for lighting in this 25mm void safe in the knowledge that his vapour barrier will not be punctured, before finally fitting plasterboard to the battens. With this construction it would be possible to achieve a vapour barrier with an Sd value of something like 100m which would effectively ensure that little or no vapour could rise up through the insulation in the first place.
I'm interested to know if your statement about cold roofs not working anymore due to insulation levels is based on your experience remedying flat roof issues or from some specific research? If it is from research please could you share the source as I would really like to read it. Thanks
Hi Steve, I do like your videos as they are full of well explained knowledge. I have a one question for which I cannot find an answer (just some discussions). I have a gable roof with cold attic. THe roof is covered by vapor-permeable membrane and ceramic roof tiles.
Under that there's a mineral wool with vapor barrier. Should I warm up the attic by putting mineral wool between rafters or it's better to keep it like that? If so, should I also protect that wool with vapor barrier? What about the ventilation?
Interesting as always, thanks for sharing 🙏
My pleasure!
Hi iv recently had an extension full wrap around the builder has laid a cold deck roof but it stayed on our specifications that a warm deck roof was to be followed on the design. The cold deck only had vented soffits but no ventilation on the building line side and no building control will not sign this off due to it no meeting Reg’s and going off design. Could a warm deck be laid on top of the roof that is there now and will this pass regs.
Hi Steve, thanks for your videos, for a DIY'er these are so informative, so very grateful for them.
I do have a question...🫣
Constructing a non inhabited shed. Walls are: (in to out) osb, air gap, reflective Vpr Barrier, 100mm 'wool', brthr Memb, air gap, cladding.
Now, my question, the roof was going to be similar,
(In to out) osb, air gap, reflective bubble insulation vpr barrier under joists, 200mm 'wool' btween joists, brthr membrane on top of joists, osb, epdm.
I didnt intend to add any further ventilation to the roof.
Cost is my main objective here as i cant afford the ideal PIR thickness etc and was hoping that spending a little xtra on reflective barriers combined with thicker cheap wool will get me closer to a better result. (Appreciate this isnt optimal, im not subject to any building control but still keeping shed low as possible)
Will that be ok, as all moisture will be 'sealed' internally? I will be using extraction combined with dehumidifier as treating water for window cleaning buisness.
P.S floor sealed and insulated
Hopefully that all makes sense
Nathan
thank you Steve, could you please give me a figure of thickness of PIR to use for a warm roof? we have a partly internal garage we are converting and have decided to go with a warm roof over the external part of the ceiling after watching many videos on your channel. many thanks
150 mm of PIR will bring it up to the new regulations
@@SteveRoofer thank you so much Steve, much obliged
Hi Steve
Just to let you know “Build it correctly” uses a still of you from one of your videos claiming these are the builders that don’t know what they are doing with flat roofs, Mr_A_ Builders have already challenged him as he does the same with them showing a still of their video and claiming they are installing flat roofs wrong
I think he’s totally out of order
It would be great to see Steve create a new 2024 video of best practice for the make up of a warm flat roof. Address the issue being argued over at "build-better-things" where a top deck of 18mm osb typically seen added by most uk builders is bad?. The argument being raised is that this osb deck may still rot regardless of whether an EPDM, GRP or Torched on felt is used as the final roof covering. I'm not interested in whether the guy is right or wrong to have shown clips of other channels, but I am interested in well rounded expert advice from people such as Steve. PS: Many thanks to Steve for your technically informative videos.
@
There are plenty technical sites on RUclips with the new building regulations, and architectural drawing’s on the net explaining the warm roof makeup
And they all state nothing wrong with the OSB being on top of the insulation
Build better things has provided no evidence to back up what he “thinks” and that’s all it is
Hi iv recently had an extension full wrap around the builder has laid a cold deck roof but it stayed on our specifications that a warm deck roof was to be followed on the design. The cold deck only had vented soffits but no ventilation on the building line side and no building control will not sign this off due to it no meeting Reg’s and going off design. Could a warm deck be laid on top of the roof that is there now and will this pass regs.
Hi iv recently had an extension full wrap around the builder has laid a cold deck roof but it stayed on our specifications that a warm deck roof was to be followed on the design. The cold deck only had vented soffits but no ventilation on the building line side and no building control will not sign this off due to it no meeting Reg’s and going off design. Could a warm deck be laid on top of the roof that is there now and will this pass regs.
Hi iv recently had an extension full wrap around the builder has laid a cold deck roof but it stayed on our specifications that a warm deck roof was to be followed on the design. The cold deck only had vented soffits but no ventilation on the building line side and no building control will not sign this off due to it no meeting Reg’s and going off design. Could a warm deck be laid on top of the roof that is there now and will this pass regs.