How To Build A Flat Roof Warm Or Cold Construction. What's The Difference?

[@garvielloken3929]

Steve bro! This was priceless info! Thanks for taking the time to share!

[@przemyslawolejnik550]

Well explained. Quick and straight to the point

[@rohan.london]

Hi Steve, Excellent video. If the roof is flat concrete, is there an issue with laying timber firrings directly to the roof then constructing a typical OSB/VCL/PIR/OSB/EPDM build up ? There is obviously an air gap between the firrings and the first OSB layer. Is this an issue ?

[@SteveRoofer]

It's unknown hell that AerCap will work with trapped air in it that's the only issue we don't like doing it because of that but as I say it's unknown

[@rohan.london]

@@SteveRoofer Thanks ! I've put a call into Kingspan to see what they recommend.

[@Sketch1994]

I just wanted to say that you are a master of your trade and that while my project is not exactly a flat roof but so far your videos have helped my planning process immensely. I am about to build a metal frame, roof over a partially underground concrete floored/walled trench that used to be a parking lot, and I want to make the ultimate yard machine shop (I already have an industrial lathe that I plan to move there, expect a gorgeous new milling machine as soon as the construction of the space is complete and plan on adding a bunch of high precision measuring equipment which pretty much leaves no room for insulation errors...so much more for condensation and leaks). The initial plan was to just add some screw through composite panels (standing seam ones don't exist in my country), but I later realized that doing only that in itself is a great way to create a huge moldy mess that would potentially consume my machines and tools. Also I realized that 3cm of insulation is not nearly enough to maintain comfortable temperatures in the windy and cold winter, and I wouldn't stand a chance at maintaining standard test conditions (23°C) for more than 2-3 hours a day without some massive energy bill My current plan after all the information you have shared (unfortunately I didn't have time to assimilate even a fraction of it since I have a 1 month deadline for the construction) is to first set the metal beam frame up with some raised joists, on which I will place the standardized screw through composite panels on top of the frame, taking advantage of the fact they don't need any subplate beneath, and then slide some extra insulation between the joints and directly above the beams. My questions are if the vapor barrier have to be directly adjacent to the first insulation layer, or if it's a good idea to apply it under the beams and seal it with some interior panels, and should I install an EPDM rubber layer between the 2 insulations, or is building a deck below them necessary to stick the rubber to? Would that be enough to make sure my hybrid "warmish" roof stays dry and leak free (vapor barrier from bellow the beams and EPDM ontop of them and under or between the insulation layers) Thanks in beforehands and keep the investment saving lessons coming! PS: After having seen your videos I might never trust a "professional roofer" again tbh, since now that I know what to look for, I know that nobody around here ever does it correctly (this is why the factory I work at has half a dozen leaks per square meter, leading to micrometer accurate precision tools, fixtures and jigs rusting over a single weekend). Also code here is pretty loose and not even remotely up to date with modern building practices so anyone is allowed to do whatever they feel like.

[@elephantear7659]

Great visualization, much appreciated, had a question, what goes on top of the warm roof insulation and is warm or cold best for a living space/patio on top of your roof? Thx.

[@SteveRoofer]

Definitely a warm roof is the way to go and definitely not using a top decking is the way to go however that causes problems when trying to turn this into a patio then realistically you have to add a second substrate under the roofing membrane

[@elephantear7659]

@@SteveRoofer I see, thanks a bunch

[@jacko4806]

What fixings should b used on warm roof installation with bottom and top decks being 18mm OSB?

[@SteveRoofer]

I always use thermally broken fixings however you don't have to but what you do have to do is use a fixing that is designed to be used externally

[@jacko4806]

@@SteveRoofer Thank you, how much do the thermally broken fixings protrude from the top and are they suitable for fixing over 11mm OSB deck? Would they show when a waterproofing system is applied? Thank you.

[@TomSullivanify]

Steve have you ever used vacuum insulation with a warm roof to save thickness?

[@SteveRoofer]

No however I have looked at it and it's extremely expensive and difficult to install so much so you don't see many people using it at all

[@lukeprice5090]

Hi Steve, with the added layer of Insulation underneath the joists where would you then put your vapour barrier? Under the joists or under the extra insultion with battens? Thanks

[@rideforever]

Thermal bridging on cold roofs can be quickly resolved using thin rubber glued to the top fo the joist and the deck screwed through or even around the top 3 sides of the joist with the insulation stuffed between. No need to lower ceiling and rapid to do. The major thermal bridging is from direct contact with the outside, airflow bridging is much lower.

[@SteveRoofer]

Unfortunately this is not correct as you need a minimal thermal performance to stop the thermal bridging i.e. on most specifications it's 25 mil of PIR insulation

[@jeromeclatot1769]

Hello i have a question i have a flat roof made of Rodman liner. And wanted to insulate better. I’ve been proposed dense packing the ceiling. And but can possibly accumulate rote and mold. I was wondering whether I should dense pack below my ceiling. Thank you

[@rexmundi8154]

Very helpful. I’m going with the warm roof.

[@jessedrukker2565]

Steve, thanks for this explanation. Am I correct that your diagram of the hot roof does not include any ventilation? Why is condensation not a problem for the hot roof? I would have thought an air space would be required between the insulation and the roof tiles....

[@50burringham76]

Hi Steve, I am having an extension built flat warm roof with a felted finish. Would it be ok to go for 18mm t&g osb staggered, vapour barrier, insulation board, finished felt product. regards

[@HampsteadBuildersLt]

base OSB T+G then Air Vapour Control Layer (AVCL) then insulation then roof covering or more OSB and roof covering, the AVCL is alway on the warm side of the insulation

[@50burringham76]

@@HampsteadBuildersLt what AVCL would you reccomend please? there seems to a be lot about on the internet

[@HampsteadBuildersLt]

@@50burringham76 alutrix 600

[@e39diy_ted]

Hi Steve, what software do you use to do these 3D models?

[@SteveRoofer]

Are used SketchUp

[@ArtificialJetleg]

Hi Steve. Nice explanation. I discovered tonight from my architect that insulation can go om top or under. What’s the best for keeping a house cool/confortable? I live in the Caribbean, where the sun is always shining with temps of about 32/33 Celsius. -> warm or cold roof?

[@leightonsmith8092]

Hello I'm glad I've cone across your videos. I'm building a garden room and been watching someone who puts the insulation on a cold roof but butts it up to the osb and has a gap between the insulation and vapour barrier that's not vented like a hybrid roof. Now will the fail or not he says that with the insulation up tight to the osb that it cant condensate up there. (Its a rubber roof) cheers.

[@robmckenna6488]

Spot on as usual Steve. Could you advise on a SIPS flat roof and which category of roof this falls into. Seems people are starting to use these SIPS panels fastening plasterboard direct below and rubber roof direct on top. Wondering about ventilation voids in this situation. Keep up the videos, awesome to share your knowledge.

[@theadoresnibblegoober6258]

Could you use spray form if you use a warm roof system and the then spray the ceiling joist and leave it open? I just want tin increase the R value because I live in canada.

[@SteveRoofer]

Spray foam is not liked in the UK so I haven't got much experience with it

[@theadoresnibblegoober6258]

@@SteveRoofer ok

[@klaeLIFE]

Hi Steve, you have convinced me to use a warm roof for my garden room. The make up I'm going for is as follows EPDM Roof Membrane 18m T&G OSB 100mm PIR Non-breathable plastic sheet 22mm Egger Protect Waterproof covered chipboard T&G 125mm x 50mm roof rafters 12.5 plasterboard Plaster Skim with downlighters cut in Does this look ok? (ignoring the roof rafter size as they are adequate for the span in the span tables for C24) Would i need another vapour barrier between the plasterboard and the rafters like in a cold roof? Many thanks

[@handle1196]

You you ever require that last vapour barrier inside

[@klaeLIFE]

@@handle1196 always in this country in a timber building. It costs about £20 from wickes

[@mattclark7700]

hi steve, how would you run cable and install downlighter on a cold roof without slicing channels in the insulation boards?

[@simondgrass]

Cables would go in the gap above the insulation, and you’d then have to chop your downlights into the insulation.

[@manoftheroad55]

Perhaps update Spec now 150mm ? ..can sound deadening mineral slabs be added..R

[@leebrierley2610]

Hi Steve I am currently building a garden room and I am limited to 2.5M I wanted a warm roof but the build up is aot. My question is does a sips panel roof solve my problem as in it is the same as a warm roof but without the supporting timbers. Cheers Lee

[@renevanbreukelen4665]

I have a cold roof construction that needs a new epdm ( rubber) or bituminous covering can I also add a lair of insulation like on the warm roof example? Or does that create other problems?

[@SteveRoofer]

Yes it stops the hot air from rising making the bottom of the decking colder and in some conditions condensation may form. If you have insulation in between the joists you have to place more insulation on the roof to counterbalance Im going to do a video on this shortly as it seams silly that insulation between means more insulation above. This only becomes a problem when conditions are adverse

[@UrminnesTider]

How do you lay a warm roof on a A-frame house that has 65 degree angle and make it stick to the surface?

[@SteveRoofer]

You use proper firmly broken fixings installed at an angle to help stop the sliding stresses. It's quite complicated about the information is out there getting in touch if you need any more.

[@UrminnesTider]

@@SteveRoofer Thank you, it helps.

[@theadoresnibblegoober6258]

Where does the Vapor go on the plywood or on top of the insulation?

[@SteveRoofer]

it gos under the insulation

[@theadoresnibblegoober6258]

@@SteveRoofer thanks,

[@michaelreed8206]

Hi just wondering can you use 11mm osb on top of joist to keep cost and weight down ?

[@SteveRoofer]

Thanks Drukker, no ventilation is needed in a warm roof, the gap between the joists is now internal in fact you don't need a ceiling. So do we vent our rooms? Yes we have a changed of air to keep it fresh and healthy. Do we get condensation in our rooms. Yes on cold spots such as windows and sometimes on walls. So wont we get condensation on the underside of the decking especially as we haven't got a ceiling? No as the performance of the warm roof is so good we don,t get cold spots.

[@michaelholt4239]

Steve, I wish we had someone like you up north (north Manchester). I spent£4000 on a warm roof with what is supposed to be the top warm roof installer around here. Okay it hasn't leaked, but warm? No way! Biggest mistake was they did not put insulation behind the fascia boards between the roof joists or at the sides (it's a dormer). After watching your videos the only way i can see around the problem is to take part of the ceiling (a 2ft width) down all around the front and rear dormer and fit insulation from below. Unless you know any other way?

[@SteveRoofer]

No sorry, don't know any other way. At least you haven't got a cold roof that's not been instaled correctly. At the moment I'm inspecting 2 a week that have been installed over new extensions or loft conversions, and no ventilation or vapour barriers have been installed. Warm roofs that have been instaled incorrectly seem to perform still better than a cold roof. I see a lot of cold roofs on extensions dormers that spotlights are just cut into the ceiling and the insulation is just cut back at that area! Nobody is thinking this through. Warm internal air with moisture migrates up around the light and into the vented area. You lose your heat, you fill the vented area with warm moist air and if its cold outside you could have sweating.

[@SpencerCrocker]

Hi, other than additional cost is there any reason not to have insulation between the joists as well as external insulation on a warm roof?

[@diluxe]

Hi , can you recommend as guide on constructing a warm sloping timber roof

[@SteveRoofer]

Sorry no if you find one send me a link please there are so many variations

[@gferguson73]

Hi Steve live the videos can I ask what software do u use to draw up you examples please

[@SteveRoofer]

Sketchup

[@immortals_1785]

Hi! I am going to do a cold metal frame what is the best way to insulate it and thermal bridling it . Maybe do a video for some metal framing too that be nice.

[@user-qp6vg9ho8u]

Great video! I’m building a warm roof on top of the existing decking on my summer house. Am I right thinking I need to put a breathable membrane on both sides of the insulation board? thanks

[@SteveRoofer]

No it's the last thing you want to do is add breathable membrane to a warm roof a warm roof should have a non-breathable membrane at the very bottom this is called a vapour control layer sometimes referred to as an air vapour control layer as it also stops the movement of air up into the installation and the roofing system that is above the vapour barrier

[@user-qp6vg9ho8u]

Steve Roofer thanks you have just saved me a massive headache. This will explain why the plywood decking rotted out on my old roof as my previous builder used breathable fabric underneath the insulation board

[@onecrazywheel]

Steve wonderful video. I live here in Central Florida in a house built in 1958. The house has a 1/12 pitch roof and several rooms with flat roof. The framing is at least 2x6 or 2x8 on 16 inch centers. The roof material is "torch down". I have zero insulation inside the roof framing and the roof was put down in 2002. We desperately need insulation. Right now we have a Whirlybird and that attic roof turbine draws a lot of heat out of the attic in the summer since the framing in the soffits each have 2 inch holes in each rafters bay. What would be our best solution? How should we go about insulating? Thanks. Great video. Jeff

[@SteveRoofer]

The situation where you are is different because of the high air moisture. Your VCL goes in a difrent place I think on the outside of the insulation you need to talk to the local building inspectors

[@chrisjp7937]

I am looking to convert my lean to style conservatory roof from the polycarbonate to a solid roof. I was looking at a cold roof system, to allow for ventilation I thought about having batons running perpendicular to the joists so I could have ventilation at the sides instead of some obscure system against the house wall. Does this sound practical? Would I perhaps be better to go for the warm roof system as I think I'd have the height available. Many thanks, great video.

[@MaximGrachev]

Hi Steve. Great video. Very informative. What do you, think. Would it make sense to make a mix of both? Meaning insulate from the inside (cold roof), and also from the top (warm roof). The insulation heights would be less, because of having them on both sides, and the disadvantage of the height problem in the warm roof would not be there. Would it be necessary to have also ventilation? Since it is a mix, maybe it could be something like the best of both worlds? Again, great video!

[@zororat]

As long as the bulk of the insulation is ontop to make sure dew point is far enough away from timber

[@AndrewHelgeCox]

What do you think about foil insulation products? Can they be used to insulate an old flat roof from below, making it a cold roof and retaining airflow underneath the deck due to the insulation being thinner than foam or rockwool? Would love to see a video on them like the one where you show traditional hot and cold roof buildups side by side on your workbench.

[@AndrewHelgeCox]

Here is a fitting guide to one product with section views: www.superfoil.co.uk/wp-content/uploads/Downloads/INSTALL/Roof_Install_Flyer.pdf

[@SteveRoofer]

Im not quite sure I understand please elaborate

[@baloo217]

Hi, i have a question, i live in florida, i have a one car garage with a flat roof like the one on this video, no soffit, so no air coming in or out of the roof when close wit drywall . my plan is to install a mini split in the garage, Summer is to hot here, i know i have to insulate my garage door, now, how should i insulate this roof and what to use, my rafters are 16" x 2" and like 15 or 16" a part, left and right walls are block and stucco, anynof the two walls are exterior, left wall has my kitchen on the other side, and right wall meets my neighbors garage, the rafters goes right thru the blocks, so no wood against any of the walls. I want to do this my self, and im scared of moisture on the roof and floors.. I hope this info its enough for you to help me out, if you can, thanks in advance...

[@SteveRoofer]

The problem with Florida and your area is I'm not accustomed to. It's weather in England we put the vapour barriers on the inside however, in some places in America, you put the vapour barrier on the outside depending on whether or not your air-conditioning inside or external temperatures you're better off reading some of the information that Joe does on his website building science, he is more US and Canada-based and will probably give you much more information

[@dogsareawomansbestfriend]

Guys insulated my bedroom 'ceilin' which had a flat roof. Looking at your sketches, is that why my room is so cold? It's the coldest room in my house!

[@hellosignprintfactor4219]

Hi great video. A question for you, with a warm roof do I have to insulate in between the joists as well before plaster boarding. ?

[@SteveRoofer]

99% of the time No. Sometimes if we have had due point calculations undertaken then yes we do but follow the specifications to the max.

[@SpencerCrocker]

I see. Look forward to the video. How do you know how much insulation you need?

[@joebadgerguitar]

Great video Rick!!

[@SteveRoofer]

Glad you enjoyed it

[@harikrishnapatel6335]

In warm roof can you also put insulation plasterboard on cilling

[@garagefaff]

Hi Steve, I'm trying to design a cold roof for a garden office (not subject to building regs) It has to be a cold roof because of height restrictions. The joists are 150 and will have 100PIR what I can 't get my head round is am I better to push the hard PIR up to the OSB so that there is no ventilation but also seal the any gaps so that no moisture can pass also or just leave a 50mm between the PIR and OSB to vent gap and not worry too much about the holes the downlighter will need...??

[@SteveRoofer]

You must have an air gap under the decking and that a gap must be vented so I can blow in one hand and out the other end this is essential. The installation must go down tight against the ceiling and there must be a vapour barrier under the installation up tight against it and it must be completely airtight completely airtight and sealed to the four walls

[@muscleprotein]

@@SteveRoofer I have an issue where the people that built my garden room had zero clue how to do a cold roof. Can I use mineral/ rock wool insulation against the VR instead of insulation board and have 50mm air space above? At their expense I am going to take the roof off from the outside and therefore will be looking down while trying to rectify the issues. I know they would have just cut the VR and pushed the spot lights into the ceiling so can I rectify this from above as well? Many thanks James

[@imran-jd1ht]

Hi Steve my builder have done the warm roof fiber glass roof on 6 meter extension after few weeks cracking noises start to come early morning and in the evening same time during the day . Can you please let me know what is the problem way this cracking noises are coming?

[@SteveRoofer]

Expansion and contraction, hard to solve have tried cutting the roof into peices and fixing with flexible sealers to form expansion joints. This reduced the problem but didn't solve it

[@imran-jd1ht]

@@SteveRoofer Thank you So the fiber glass roof is not a good option then and what is the best option to solve this?

[@SteveRoofer]

@@imran-jd1ht remove the GRP lass fibre roof and start again

[@daintree81]

Fantastic videos. I have a outbuilding which I am converting into a gym with a new warm roof. The building is 2.5m by 7m long, I was looking to use 50mm by 200mm joists running the 2.5m length with spacing between the joists of 400mm (can i have a larger gap?) 18mm osb board on top of the joists, dpd membrane, 120mm insulation, epdm roof. The slope needs to run down towards the longer end and I was wondering if i could just angle the joist hangers which will be attached to the brick wall at an angle to get the desired slope or do i need to have Firrings? Keep up the good videos.

[@SteveRoofer]

I wouldn't go wider than 400 as you don't want roof to sag in a year or so get the fall on the roof whatever way you find easiest firings or joist hangers

[@garycoyne9747]

Hi Steve, excellent level of detail gone into all your videos. Really interesting. I am going to construct a warm roof but I have a bit of a height restriction, I plan to use osb Vaper barrier - Insulation - osb combination. I will probably only get about 100mm of insulation fitted and was wondering if I could use foil type multlayer insulation in place of the vapour to act as extra insulation in a thiner design and as a vapour barrier which brands like superfoil claim to do anyway. Thanks in advance. Gary

[@SteveRoofer]

You should reach out to the suppliers of the multifoil and get them to give you a specification as this is going to be a bespoke build. There are specifications for flat roofs that we no work are robust and have some built in redundancy, specifications for flat roofs that we think work and specifications for flat roofs that don't work. A good warm roof will work even if mistakes are made. The key to all of this is not so much the vapour barrier but making sure the vapour barrier is airtight hence now you will see a lot of talk about airtight vapour control layers AVCL,s.

[@garycoyne9747]

@@SteveRoofer Thanks Steve.

[@osobogly]

Hi Steve, amazing videos and info! We have an addition in Utah with 16" BCI joists. We have dry summers and winters. The old roof was an insulated/vented 10" cold roof. We planned to copy that method but many suggest the hot roof methods. With a 6 " difference in old and new roof heights, we'd like to avoid more height. Is it feasible to put foam insulation between the flanges (underside osb) and leave an air channel between the foam and a standard bat insulation for venting since there is so much height in the 16" joist? Or would we be better off to do fully spray foam insulation inside?

[@SteveRoofer]

Just do cold roof insulation between joist vent above pay attention to the venting and make it really good. Also ad a good AVCL to the underside

[@angelicaphurtado5980]

Hi Steve thanks for the videos they are great! they have been a guide for me as I got to design bc drawings for a loft conversion for a terraced house , would like to go with warm roof but height will be problem after proposing new flooring level as well :/

[@charlesscottkelly]

Thanks for this great information 👍

[@SteveRoofer]

Glad it was helpful!

[@canonicaltom]

Pretty wild seeing all these comments talking about height restrictions. In my area, can't go higher than 10 meters above grade without a variance, which is easy to get. What would you say is the highest performing roof assembly from an energy standpoint?

[@SteveRoofer]

Warm roof construction is the cheapest quickest, easiest and best, but has to be installed correctly

[@canonicaltom]

@@SteveRoofer Thanks. It gets down to -50F here in the winter, what sort of detailing do you recommend?

[@SteveRoofer]

@@canonicaltom a robust air vapour control layer with 200 mm of PIR over the top with something like EPDM rubber over that

[@warrenely7708]

Can I ask what the OSB is used for in the cold roof? I'm doing a cold roof in a conservatory and I don't doubt my skills. I spoke to a private building control firm and they said OSB isn't really needed.

[@SteveRoofer]

In a cold roof its the roof deck you lay the roofing material on

[@warrenely7708]

@@SteveRoofer I'm using Tapco lightweight tiles they suggest OSB aswell. I think I ill go with using it. Thanks for the reply.

[@SteveRoofer]

@@warrenely7708 I worked on a job with them once and I liked the look of them. Make sure you install them the way the manufacturers tell you. Think about venting the roof. I would love to see photos from start to finish and your opinion of them. Send me any info you want if you want my opinion

[@txter0]

Hi Steve I have a kitchen extension that has been converted to a pitched roof. What they have done is take of the felt and leave the flat ply base. And create a pitched roof above it with a wooden frame and tiled it. The sides have been closed up using pvc cladding, it looks very nice but there is no insulation in the roof. Would I be ok to create a warm roof on the plywood base but obviously not put the felt on as it’s already waterproof. If I insulted between the rafts the space above my kitchen would still be very cold because of the cladding on the sides. Any advice would be appreciated. Thanks

[@SteveRoofer]

What you are creating is a cold roof the space above the insulation is eternal Cold, space below is internal warm. Vent the cost space. Stop all movement of air into the warm space

[@txter0]

Ok thanks, would I still need to use a vapour barrier ?

[@SteveRoofer]

Yes the vapour control layer on a cold roof goes above the plasterboard

[@jammer5007]

Hi Steve, I've built a shed 3m x 3m but due to height restriction have opted for the cold roof. My question is noggins that are in place because of the span of the build and to keep straight the joist they also now block airflow. To create adequate airflow through the roof whats the best way to do it.. is it a case of creating holes through the noggins but above the insulation.. any advice would be much appreciated Cheers

[@SteveRoofer]

The noggins don't have to be full height or cut holes in them

[@jammer5007]

@@SteveRoofer thanks Steve.. just saw another video of yours about cutting holes through joists to create airflow... excellent videos, very helpful Cheers

[@timothypreston2455]

Is there any disadvantage to installing insulation between joists and having a warm roof construction. This way there is maximum insulation?

[@SteveRoofer]

Putting the insulation between the joists forms a cold roof. If you put the roof insulation between the joists you must put it in the lower part of the void and vent the top. To get the correct U value and to stop thermal bridging you will have to remove the ceiling and replace with insulated plasterboard, reducing the room hight.

[@TheCazwalker]

What about if the full void between the joists are insulated? Surly that is another option?

[@booshallmighty]

Hi Steve, you really convinced me on the cold roof. I'm building a timber frame man cave in my garden. The problem I have is the 2.5m height limit. My bas is already about 10" of the ground. I need at least 2 meter ceiling height . The recommended roof joists are 8" then I would like to put firring strips on top of those so I don't have a sloping ceiling. How would you solve this problem? Could sips be laid across 4.5 meters unsupported? Thanks Steve, your videos are really helpful. I wish I could afford you to do my roof. Thanks again.

[@SteveRoofer]

Yes if the supplier designs them to span that width, unfortunately everybody has this problem with height on warm roofs

[@solo-repair9374]

Hi just out of interest what decision did you make on the roof.

[@tomwalke4477]

I'm having a similar issue. I read somewhere that a warm roof can be achieved by fully insulating between the roof joists. Mine will be 150mm so basically the make up of the roof on my design will hopefully be OK? Plasterboard Joists fully insulated in between 18mm osb Epdm rubber roof membrane My only concern is will I need to have an insulation between the plasterboard and joists? HELP :)

[@klaeLIFE]

@@tomwalke4477 Surely that's just an unventilated cold roof. The timbers would be cold.

[@reggiewac]

Spot on as always. Keep 'em coming!

[@project3430]

Hi Steve - I need to go the cold roof route on my workshop due to height restrictions. I have been led to believe that the roof has to be vented across from one side to the other with a 50mm gap between the insulation and underside of roof deck - my question is that when I fit noggins this will effectively stop any cross ventilation as the noggin is the same size as the rafter - any ideas of how I get round this or have I misunderstood the entire concept ! Thanks

[@liammulcahy9506]

Drill holes in top 50m of noggins, 3 holes per noggin, air will then circulate through each noggin.

[@project3430]

@@liammulcahy9506 - thanks, all sorted now

[@lawrencewhite4362]

@@liammulcahy9506 hi Liam! I have a couple of similar questions, if you think you could help.. my rafters are 125mm (5x2), as will be the noggins, and I'm planning on drilling holes near the top of each.. my question is, should I also drill holes in the noggins, and also, should I get 120mm Celotex, completely filling the depth of the timbers, or should I get 100, to let the air flow..??? Any help appreciated! Best wishes, Lawrence (home improvement enthusiast!)

[@liammulcahy9506]

@@lawrencewhite4362 You have to use 100 mm to allow the air to flow ( 100 mm is what is recommended for a roof, and is plenty) You really only need to drill holes in the noggins if it is an outside room /shed. Air will flow along the direction of the rafters , through the holes in the noggins and out of either end of the roof.

[@preyashdesai]

Great explanation as always. I am planning to convert my existing cold flat root to warm flat roof (EPDM rubber). I have called the council (Solihull) about the planning permission and they said if the height is going to be more then 150mm then existing roof then you need to apply for PP. As going to cold roof to warm roof height is going to go up , do you think it be more then 150mm ? I will need BR in any case. PS if only you were to provide your services in midlands :)

[@SteveRoofer]

120mm of insulation with 18mm then total height for a warm roof around about 138 mm 140 mm so you're well within side what the local authority are asking for.

[@preyashdesai]

@@SteveRoofer That makes sense. One more que. As the current trimming was designed to the height of the current roof. How do I componsate for the new height of 140mm ? Is it with removing existing trimings (currently I got white pvc trimmings) or just put another one on the top of existing one?

[@SteveRoofer]

@@preyashdesai Yes new fashias and flashings and probably raise the guttering up so its under the drip edge not way down in the old position

[@preyashdesai]

Thanks @@SteveRoofer . Just one more que. I have found out that the roof (build in 2001) is infact warm roof and it already has 75mm insulation. In order to replace it with 120mm insulation (another 50mm extra) do I need to increase height of side facia boards or is there a trim available which can accomodate this 50 mm extra height?

[@SteveRoofer]

@@preyashdesai There are trims you can use but on warm roofs the trims start to get big and ugly as the hight increases

[@elliottdebell7783]

Great video

[@lisaperizzolo8914]

I need help. I think my carpenter placed the joists in the wrong direction and has no ventilation on either end of them to create a cold roof. He won't admit his mistake and now I have to have a ventilation on top and drill holes in my joists to create air flow. can someone please help me know how big of a hole I need to make. I think he also used 2x6 for joist. I am so done with him I am willing to make the holes myself.

[@leebrierley2610]

Hi Steve I am currently building a garden office and wanted a warm roof but I am limited to the 2.5M my question is would a SIP panel roof not be the same as a warm roof just without the rafters ?? As it is structural. Cheers Lee

[@leojk4321]

The other big advantage of Warm Roof is that Every MEP engineer loves to run all services inside the empty roof. When they see it, they just love it, because you can basically run there everything from pipes to lamps. Also, with the cold roofs there is another issue: trying to keep the integrity of insulation. Once the Electricians start to drill holes in the lower insulation, then the problem starts. It's nearly impossible to make it perfect with cold roofs. And in 9 out of 10 roofs contractors somehow manage to forget about ventilation until the last moment. We spent most of our year in correcting cold roofs ventilation by simply drilling holes in firrings after a few years when the moisture starts accumulating and become visible. 😅

[@SteveRoofer]

Yes you are correct but drilling holes in not that good doesn't offer the best ventilation but better than nothing

[@fredatric]

Very informative, thank you.

[@highgatehandyman6479]

Legendary. Some helpful

[@gdfggggg]

Very good

[@agt155]

Could you not just have the insulation between the rafters pushed tight up to the board. Would be like the best of both.

[@kylew1001]

Hi, do you recommend adding insulation below the joists as well as between them? In your lighting video kzbin.info/www/bejne/gl7LiZqMaZmio8U I can only see the insulation between the beams and not under them/on top of the plasterboard. Many thanks.

[@py_tok5589]

cool bob the builder

[@SteveRoofer]

thanks