How to put a flat roof on a garden room

Hi, Ive compiled 3 videos into one, so sorry if you've seen before! Just thought it might be easier if its start to finish, instead of jumping from one to the other. We are putting a flat roof on this garden room with a 75mm pitch over 3mtrs to create the fall. Timbers used are 5x2 c16, We can't use bigger timbers as this would bring our building over the 2.5mtr height limit. So, we are on the max size possible, they are at 400mm spacings and fixed with 90mm pas lode nails and upside down joist hangers over the steel. roof covering is OSB3 T&G boards that are fixed down with 63mm ringlet pas lode nails and glued with polyurethane glue on the joints. We then fix fascia and soffit all round to complete the roof structure ready for the rubber roof! Hope you enjoy and thanks as always for your support!

[@jakublengiewicz6704]

Thank you very much !!! Really helps with my construction! Plenty of great tips , thanks for taking your time to do these videos

[@simonmiddleton2990]

It amazes me that you get trolled for making very detailed videos helping people , love the channel and all the invaluable knowledge you have provided , i have every confidence i could now build a garden house purely because of you .Many thanks .

[@davidhopwood7491]

Awesome work.

[@plummetplum]

This was exactly what ive been after, i was going to make some firrings fir the side but your method is easy and quicker. Much appreciated Liam.

[@bwq1we482]

Re-watching as I go along with my buildpack. Thanks for the videos and the detail 👍

[@jerrymoffat3966]

Neighbours can be a pain in the backside. It’s usually out of jealousy. It’s easier to work with them if you can. My son’s neighbour built a large extension. My son was a bit concerned, I told him as he will get it done anyway don’t fall out. Extension is built, looks good and they are all mates still, as it should be. Great build Liam, shame there’s always an AJ about.

[@stephenfuller1066]

Another Master class. Thanks Liam

[@markbailey3027]

Your videos are invaluable, thanks for sharing your knowledge. Hopefully I'll have something built, if it's half as good as your builds I'll be well happy

[@mikebray6402]

Another awesome video. Love watching these, please keep em coming.

[@johnnyg1700]

Very well explained. Your tutorial has given me ideas for my garden workshop...Cheers 👍

[@brad30]

Your workmanship and pride in what you do is outstanding. Keep up the great work and content 💪👍

[@thegardenroomguru]

cheers mate!

[@titanclass3895]

@@thegardenroomguru you need to go NATIONAL!!!!

[@georgemcintyre007]

A1 videos with great practical advice

[@staceyismine]

Your attention to detail is second to none who ever showed you the ropes should be proud. 5* William

[@garethbrooks3301]

Great video, very informative. Thanks for explaining it clearly. Cheers

[@kashhameed3067]

Fantastic videos, learnt so much, will be attempting my man cave hopefully soon 👌🏼

[@tonymcfeisty2478]

love the way that's put together, very similar to a 5m x 4m shed I self built, I did build it on 2 courses of engineers, on a concrete pad, like the fact you used a good solid sub fascia. was supposed to build a summer house last summer but a back injury put paid to that, will be going pitched roof with a rear hip when I finally get around to it.

[@psymon25]

Amazing work

[@bobfletcher8196]

Great video it’s made me realise what a bunch of shoddy twonks were working on my daughters house.

[@RE5832]

Incredible work as always love following your chanel

[@traceynicholson6774]

I love your videos and the best bits are fixing issues and the fact everyone measures wood the wrong length, someone like me who has just started bigger diy projects is a life saver and you always get the experts who think they know everything 🤦‍♀️and know nowt ,,, And swing hammer 🔨 is the bomb , Thank you 😊

[@soulsympathy]

thanks for sharing this valuable video I have modelled a full garden room in sketchup thanks a lot

[@michealosullivan6135]

Excellent videos with amazing detail, thanks a lot! Looking at building my own, one thing I was wondering was, is treated timber needed for the wall stud work?

[@smitims]

Love your videos mate, learnt so much. You're a top man.

[@ottonoble809]

This gezzer makes this shit look so easy just shows you the skill he has hat off to you sir

[@lhch]

nice video thanks 👏👏👍

[@MADTheTreeRoot]

Wao thank you bro that valuable information

[@1jamessouth]

Been watching these videos for a couple of weeks now. Think the detail and information is great. Is the steel lintel necessary or is it needed for the doors you use? Hope you keep up with the content!

[@slhorseboxesltd7188]

Love your work pal looks like a real quality job, think I’ve watched all your vids now and noticed on some roofs you fit the 2 end roof joists directly above the side walls with a tapered timber between the wall and roof to carry the weight and on others like this one you’ve placed the 2 end joists in line with the inside edge of the internal wall then placed timber on the back of them fixed to the top of the wall, both do the same I suppose but wondered why you have 2 ways of doing it? Hope this makes sense? Will be buying a build pack from you when I decide what size I’m going for, keep up the good work. Anthony.

[@adrianwelch1435]

good video

[@user-my9yn4yn6y]

I’ve just finished using the Skyguard 1mm membrane on my shed. It’s great stuff but it is tricky to get it to lay smooth and flat since it’s so thin. I thought it wouldn’t be a problem since it’s only 2mm thinner than most of the normal commercial grade stuff for garden rooms etc. But you really to make sure there are no bumps and that you glue the bumpy joins down with lots of glue and pull the edges tight and then fix the fascia trim or it will be bumpy on the edge. Also I would really recommend tongue and groove OSB3 as the join between the two sheets is often very noticeable when joined up.

[@jonathanviaene7237]

One sub extra!!! Thanks for the info!

[@newlinkdirect]

Buy a nail gun, I love "Milwaukee M18FFN 18V Fuel" costs same as paslode, sell on ebay after, cheaper than Hire shop. Been a God send ( base frame/ studwalls / joists / Battons for cladding) , can't imagine hammering in over 2000 nails. Excellent video Liam. thx for sharing your knowledge....

[@jamiemcneill3930]

Hi William, fantastic videos keep up the great work. Is the Steel beam fixed down onto the timber below in any way?

[@chrisoxley3617]

Excellent video. How did you get the rafters flush on the wall plates, and still manage to create the slope of 75mm over the 3 metres?

[@cathalmurphy4496]

Brilliant videos. Out of curiosity, why do you use tongue & groove osb on the roof instead of large 2.4 x 1 2m sheets of osb? Thanks

[@jackrichardson6105]

Hi Liam, first you and your craftspeople are amazing. I'm eventually building my studio following your guides. I'm thinking of using metal on my roof, wondering if you have ever used it? If not what are your thoughts. I love the way it looks and also the sound of the rain.

[@allenkimber3326]

Hi, Thanks for doing a great range of videos, I am going for an ambitious build of approximately 4.5metre deep x 9 metre in length I know I might need planning, but my question is what should I do for the roof span as far as doubling up the roof beams, do I just bolt together 2 4800mm long joists or should I be putting an I beam in the middle .

[@gkelectrical1]

I’m guessing you did the 4.5 metre span ?

[@psk2b]

Would it be suffice to use 6x2 doubled up instead of steel lintel for a 3m door opening?

[@RubenWoodcraft]

thanks again for another goldmine of information. I'm planning on building a 5 by 6 meter workshop using your video's as a guide.

[@TurinTuramber]

Make sure you get help or do your research when designing the roof. 5x6 requires careful consideration.

[@thegardenroomguru]

id put a universal beam across the middle, divide the roof into two 2.5mtr spans.Thats what id do anyway ;-)

[@TurinTuramber]

Assuming it's a flat roof (aiming for PD?) then yeah split roof with a UB. May end up with a boxed in beam across the ceiling. Has to check what size UB to use to span the 5m or 6m. Hope you aren't too tall.

[@thegardenroomguru]

Geralt of Rivia they need to increase the height to 3mtrs, but you gotta do what the rules state 🤷🏻‍♂️

[@TurinTuramber]

@@thegardenroomguru PD is about getting floor as low as possible, ceiling as high as possible and keeping the roof height within regs. That's the challenge.

[@vajindertaak3158]

Hi Liam, best series I've seen with loads of valuable advice, priceless!! It just gets better and better, and love the work rate. Will start my garden office in April. I've seen some roof designs with cladded sides (no fascia) and a front fascia but with no roof trim visible. How does the EPDM fix to the edges?

[@thegardenroomguru]

Not sure what you mean tbh, are you on the facebook group? If so post a pic on there and put my name and I’ll see it

[@bells1969]

Just asking I’m thinking of building a 4.5 x 2.5 metre with the roof hight at 2.4 meter The back and 2 sides would have no access being built in a 2x4” frame what would you recommend and what sort of price do you think I’d be looking at or would it be cheaper just to buy a log cabin kit thanks and keep up the great vids

[@TurinTuramber]

I have done a few of these over the years, appreciate that everyone has their own solutions. What makes you pick box section over say a UB19? Personally I think an I beam can be made better insulated. Thanks for the video.

[@thegardenroomguru]

Just preference mate, each to there own I suppose, you can fill the beam with rock wool, tech screw wood to the face

[@chrisoxley3617]

Hi fantastic video, very well explained. Is a 75mm pitch over 3mtrs not too flat? As in, will this slope/angle allow the rainwater to fall down the slope?

[@philipdavis9579]

William thanks great video ... where do you purchase soffits fascia and rubber roof ? Thanks Phil

[@petercallahan4006]

Great videos. Thanks for the content. Wondering why you bother using glue for roof plywood? It seems if it’s nails down, it doesn’t have ability to move very much. Just curious.

[@DrSteveGames]

Do you guys do cold roof or warm roof? (Insulation witching joists, or as a slab on top?)

[@adamandlorraine]

Do you plumb cut the ends of your rafters or leave everything at 90?

[@myatix1]

How big do you think the roof rafters need to be for a garden room that has a 5m span? I was thinking 47x195mm? But this means the roof will be huge and reduce the ceiling height due to the 2.5m hight limit? Great channel keep up the great work!

[@jaydaawg.8191]

Hi. Did you Insulate the eaves at the front before soffit went on?

[@paulyoull5472]

Hi, does the rubber roofing work on the caberboard or does it have to be OSB3

[@Robbie-fq9zr]

Hi mate. You mentioned that you should double up the timbers if the roof is larger. I am building a 5 meter roof. Should I double all timbers. Cheers

[@cjoy1976]

What type of foundations did you use so close to that big tree? (Sorry if this is in another video)

[@hkinniable]

As an alternative to the OSB tongue and groove roofing boards you use, can one use standard 18mm OSB boards without tongue and groove for the roofing?

[@markveganism5003]

My span is 4.3 ..I'm using 5x2 @400 centres ..did u say I'd need to bolt 2 together over that span ? ..gonna put the cost up a good bit

[@w84it69]

What is the overhang from outside osb to outside timber if using 300mm soffit and 18mm cedar? Any help appreciated. I am going 150mm over hang back and sides but cannot work out the measurements. Sorry just a scaffolder

[@MatchboxGarage]

Great advice for buying/reselling. I want to build a shed but was put off by high prices for a nail gun that ultimately I will only need to use once. If I buy a used one, use it once and resell it, I should get my money back 🤔

[@andyblackpool]

Hire one?

[@DrPepper22222]

Just use a hammer mate it does the same job! Obviously it's worth the expense if you build a lot of them like he does though!

[@karlsmith4245]

Hi Liam, love your videos and they have really helped… Im currently planning a yoga studio / garden room and need to get the internal hight but not go over the 2.5 rule. Could you guide me on the roof part please. I’m building on a concrete base and planing to insulate the floor with celotex 25mil ( would you go to 50 mil?) and underfloor heating. My build is 6.5m by 4.5m span what would you do for the roof joists and floor? to get the max height external and max Hight internal for yoga. ? I appreciate your a very busy man, if you could help in any way I appreciate your guide. Thank you in advance

[@shanzeumar9280]

Hi /Liam you are amazing . Can you show how to install the air vents on a flat roof please 25mm which is legal requirement(LCC)

[@Roy-hk9ru]

Maybe a silly question but when u say if it was over 3 meters you double up on the joists...would that mean placing 2 next to each other? So essentially making it a 5x4?

[@thegardenroomguru]

Yes mate, bolted every 400mm

[@andrewkilby-yr2fg]

Hi love your videos what’s your thoughts on expansion on the joints on the OSB boards.It says on there site that your supposed to leave 2mm gap on each edge even if you used edger thanks

[@thegardenroomguru]

Never had an issue mate, if it was butting up to a brick wall say, then maybe, but it’s got no resistance at any point so it’s fine

[@stephenpeacock2627]

Wish you were near Reading. Would get you to build me a garden room.

[@adrianroebuck6497]

Will, another great video. I’ve started my build so this is excellent. You mentioned at 9:58 you’d ordered the wrong roof timbers and ordered 3.6 and should have ordered 4.2? If the room is 3m deep then isn’t the total length with overhangs 3.4m? Also, with the joists is your spacing 400 on centre on are the gaps 400mm? Cheers

[@thegardenroomguru]

No mate you got the depth of wall, battens on the outside,

[@adrianroebuck6497]

Ah so the 3m is internal? I’d assumed it was external. So your 100mm rear overhand and 300mm canopy are measured from the batten and not the wall.

[@alankinehan5477]

Hi, loved your tutorial. Quick question, would you use marine ply over OSB 3 if money wasn't an issue?

[@thegardenroomguru]

For what purpose mate? The OSB3 roofing boards are designed for this job👌

[@garvielloken3929]

Nooice!

[@ITryTo]

nice vids keep them coming, i think its hard work to film and do work lol, how comes you dont use furrings, thanks

[@brendancoyle4643]

Another great video, I’ve probably a dumb question. Why do you need a overhang on the roof? Can you just have an overhang at the lowest wall for the gutters?

[@thegardenroomguru]

You don’t need one mate People like the lights and it keeps the weather off

[@brendancoyle4643]

Cheers William, keep up the good work.

[@sammydiy4503]

I’ve been watching your videos and am now considering a diy option 😳, all the videos I have watched are rectangular rooms, but we would want an L-shaped room measuring 5x7m narrowing to 3x3m (if that makes sense) and wondered how to go about doing the roof and maintaining an open space inside (no dividing walls, just external walls) can you help? Are you able to provide plans for this layout? Thanks

[@stevefenn1725]

I was going to ask a similar question, and also how to you go about pitching a l-shaped flat roof?

[@spencebespokedreams]

How much does it cost to build? An how much labour?

[@BHP15]

can we put the length of the rafters not in the direction of the roof slope? in other words, if the slope is from front to back, can be rafters installed in the direction of side to side? i am thinking to support the angle of the rafters with triangle support. no one walks on the roof after installing and painting with ultra flex.

[@MJCthepilot]

Thanks for posting this video. You mentioned about a span of more than 3m and you could provide help in this? Would it be possible to span 7m using double joists or would that require post-joints to I-Joists?

[@MJCthepilot]

Sorry Posi-joists

[@liamelton8301]

Hi doing a rubber roof for my garage. What over hang shall I do. 300mm front but not sure on the sides and back??

[@thegardenroomguru]

just enough for a 100mm soffit, with only 50mm showing, no trimming and it looks subtle

[@vestaxpdx]

28:45 What happened about the height dispute?

[@michaelwaite4367]

What size are those roof timbers? Cheers

[@joepritchard5407]

What size timbers have you fitted for 4.8m span roof if it was domestic only?

[@carlwebb6690]

Quick question mate if I use firring strips on my garden room that run from 100 - 50mm can I use joists that are 50mm smaller than the required joist for the span ?

[@thegardenroomguru]

No mate, the furrings add no strength to the roof joist 👌

[@joshuacallis3136]

Great video! with the 1200mm roof and base etc, taking it to 2400mm plus 2.4m walls inside. Would take it over 2.5m mark. Didn't catch in your video, is the inside of the room less than 2.4m say 2.1m etc? i'm thinking Inside 2.2m c16 1200 x 2 (roof and base) ebs 18mm (roof) Making it less than the 2.5m limit Also looking at c16 95mm instead, is that something you've done (p.s DIY, never build an office before) :)

[@ellis350]

Hi bud, don’t know if you remember but I sent you a time lapse vid of my garden room based on your design a couple of months back. Cannot progress until B&Q deliver the windows that were ordered 6 weeks ago but apparently there is a shortage of plastic at the moment. They should go done to the coast in the North East, there is shit loads there to be picked up. Followed your instruction to the letter so far and loving the construction so far. Didn’t go posh aluminium but I might have had the windows by now if I had. Keep up the good work and hopefully see you on the TV soon.

[@thegardenroomguru]

Big Elbow’s Emporium I do remember mate, loving how so many people have built their own and if I’ve helped in any way, then that’s a great thing! There’s a lot of materials still on a go slow at the moment mate

[@AlexPeka]

Could someone explain to me what situations demand screws over nails?

[@sdsfulham]

Would you put a gutter on the end

[@jratcliffe002]

Do I need to use upside-down joist hangers if I have no steel? I have 90mm nail gun to nail through

[@thegardenroomguru]

No mate

[@nocab865]

Any reason why you use twist nails instead of screws liam. Cheers

[@robertruddock2410]

Twist nails have greater shear capacity then screws. Never use screws!

[@johnlerigo9703]

5x2 ok for that span ?

[@martincook5079]

Love the video. Making my own based on your system. Express deliver the doors next week. Any chance of some tips on installing windows / bifolds? Its the one thing missing from your vids. Otherwise ill have to use the force to guide me .....

[@waynemace5487]

Had any visits from HSE

[@colsinclair7793]

How do you insulate it to keep the heat in without melting the snow on the roof in the winter months. 🔦🚁

[@thegardenroomguru]

🤔 🚬 🤪

[@colsinclair7793]

william griffin lol 👍🏻 I'm only fkn way u m8. Most people I know with garden rooms use them for chilling out& growing in the secrete hidden side room.

[@danjames1663]

Do you have to use nail gun or could i use screws?

[@thegardenroomguru]

Course you can mate, we use nail guns for speed 🙌

[@JarodKiefer1]

If the slope on the ceiling inside the building annoys you then why on earth did you not build out the ceiling with blocks to allow for it to be sheeted level? Excellent job even with the slope who cares

[@RPJustkeepmarching]

Any updates on the generic plans for the garden rooms William ?? Ready for a 7x3 when you are!

[@thegardenroomguru]

hi, its been a busy few weeks and ive had the kids every night for the past two! im currently sat drawing up the floor plans as we speak. Ive a new laptop on the way so I can work from the van and process the plans whilst im taking an hour off site as im currently not having any me time! So, in short , they are imminent, thanks for your patience.

[@RPJustkeepmarching]

william griffin thanks for the reply and info pal. I’ll wait for your signal 👍

[@skynewsisevil5751]

How did you get on with the neighbour ?

[@skutty5773]

Action man

[@upelectrical19]

Hi mate what is the advantages of using the smaller OSB board? Instead of a sheet of 8 x 4... cheers mate.. Great content! Keep it up😃

[@SuperPrimecut]

i love your videos i think i have the same perfectionist attitude as yourself so can relate but i think your knees need protecting when your working or they'll be shot by the time your 60 +

[@Ross0s]

what happen with the nosy neighbour?

[@ginoonig4126]

Wasnt this vid posted previously

[@thegardenroomguru]

Put all 3 into 1 as getting questions relating to other steps I’ve already posted 👍🏼

[@jix177]

29:45 AJ is blocked? Well I guess that should keep the number of comments down anyway lol!

[@garvielloken3929]

24:43 😂😂😂😂😂😂

[@titanclass3895]

Voice?

[@tomfielding3148]

What’s your email mate, I’d love a job with you. I’ll send my CV over if you ever need anymore staff.

[@thegardenroomguru]

[e-mail] 👍🏼

[@tomfielding3148]

william griffin CV sent 👍🏻

[@paulllewellyn5326]

Great work guys but I would really avoid putting the nails in your mouth! I’m a nurse and I’ve looked after a couple of guys who both inhaled nails, so perhaps more common than you might imagine.

[@SteenHolm134]

25 millimeter/meter...?! That's not much dip... I am using 10cm/100cm-10%

[@thegardenroomguru]

It’s plenty, the maths for internal head height/ timber sizes/2.5height limit and roof fall are all at play

[@SteenHolm134]

@@thegardenroomguru I don't understand what you mean. Roof fall or dip is everything... rain and snow MUST come off. Your skills and energy are otherwise verey impressive. Nice work

[@thegardenroomguru]

Rain runs off no issues, snow will when it thaws. Overall height on permitted development is 2.5mtrs, we push the boundaries on timber span sizes to the max, therefore if you pitch the roof more, you will have less than 2.1 mtr internal head height(6’8”) obviously this would be a problem so this is the max roif pitch, besides, it’s a rubber membrane, no joints, it’ll never leak if it had standing water, but at that fall it doesn’t

[@SteenHolm134]

@@thegardenroomguru thanks for explaining. The rubber seal is to me i DK, another funny material. But Rockwool I can relate to. I grew up eating it for breakfast every morning...

[@thegardenroomguru]

@@SteenHolm134 🤣