Garden Room Workshop: Part 9. Flat roof structure

[@stephenderby7582]

This is an amazing resource for a keen DIYer such as myself. I was pretty worried about getting the right pitch of my flat roof in my design.....and then you tell us about firring strips! I have never heard of these before but they have completely solved my problem. The gift that keeps on giving! 😂👍🏼

[@AliDymock]

It's the little things :)

[@Keiron12]

Fantastic series, thanks for sharing

[@BAHATI1943]

What a superb detailed series of videos. Theory necessary and explained to perfection. Keep up the good work and thanks for taking the time to produce the videos.

[@timmade]

This is so great. Thank you for posting. I have been looking for examples of this being done in the uk rather than just the states for ages.Can't wait for the next instalment.

[@AliDymock]

it's up now, I just haven't linked it to this video yet!

[@timmade]

Just watched and commented. Thanks. Would you consider releasing your sketch files?

[@AliDymock]

Sketchup? As mentioned in a previous video it's not particularly detailed, but sure! How do I do that?

[@timmade]

Hi Looking forward to the next video. I hope it is going ok. You could upload a copy to dropbox and publish a public link to it here. I think you can do that in the comments section.

[@AliDymock]

If for any reason it doesn't play correctly on youtube I'll look into that. Just editing part 11 at the moment.

[@paulboyle9605]

Outstanding again. Well done Ali 👍

[@AliDymock]

Thanks Paul, very kind of you to say. Hope it's useful for you.

[@carlosrivas5522]

Just wanted to say hello from Dallas. Learning a lot from you and looking forward to doing a similar project like yours! keep the videos coming! amazing work!

[@AliDymock]

Thanks Carlos! I noticed I had a few US subscribers which is great as I learnt all this from watching American youtubers. You'll have to ignore all the building regs/planning permission stuff as that's UK orientated. I think you have 'code' over there? I enjoyed Dallas, great to see people walking around in cowboy hats!

[@carlosrivas5522]

Actually, my regulations/permissions are similar to yours regarding size, location in the garden and Max. Height. but the limits are reasonable and sufficient for my needs. I like your ideas for the roof!

[@AliDymock]

Interesting! May I ask, do you have PIR insulation over there, I’ve never seen anyone use it?

[@carlosrivas5522]

Yep. found it quickly on the home depot website. about $20 for a sheet of 4x8 (feet)

[@AliDymock]

Gosh that's cheap! 😤

[@spencefrederickweddingphot7791]

Thanks for taking the time to make these. I'm starting a similar project and not having done one before it's pretty daunting. In depth videos like this are a great source of information (and confidence!) Can't wait to see the finished project but enjoying the stage by stage process. Great work - thanks!

[@AliDymock]

I'm really glad it's giving people confidence, that's fantastic-exactly what I wanted 👍

[@mariah4451]

I was recommended your channel by Rag 'n' Bone Brown in his latest KZbin Vlog and I'm so glad he took the time to do that. I've watched a lot (A LOT) of workshop build videos and your series is by far the most informative and skilfully produced. You've clearly spent a lot of time and effort putting this series together - I hope it goes on to reach a much much bigger audience because this series is a gem. I can't wait to see what you create and build in it. :)

[@AliDymock]

Wow what a lovely comment Maria, thank you! The number of new subscribers who came over from Keith’s recommendation shows that there are people interested in this subject, they just haven’t come across the videos yet. Quite a way to go yet, but really looking forward to doing some proper woodworking too!

[@mariah4451]

Ali Dymock, you deserve every success. I don't know how it all works on KZbin but this series would be invaluable to anyone embarking on this type of project so I hope it starts appearing everywhere and your subscribers increase week on week by at least the number of screws and nails you've used so far :) I love the music you use too :)

[@scottmclean4237]

Watched for 2nd time, good work there . Looking forward to your nxt update.

[@coreymcniel3390]

Stodoys is full of awesome tips. Very helpful to me.

[@danielbilodeau521]

Amazing series Ali! Question about the space between the roof joists where they extend into the overhang : Did you only use PIR insulation or is there wood blocking as well between the joists? And why?

[@bhco]

This video is awesome, really helped me thanks!

[@marianoserrano90]

Hi Ali, happy to have found your videos which are helping me much to design my garden house, smaller than yours, it's going to be 3x4 meters, with flat roof, but i want it to be walkable to use it as a terrace. I wonder if you know what would be the distance between joist to safely support the weight of 4 persons? Thanks in advance

[@keefykeef]

Another great instalment! 👍

[@terrywhite8087]

I never seen any mention of ensuring the crowns are facing up!! For that span it is very important to prevent sag.

[@AliDymock]

It is important. I mentioned that in Part 5 for the floor joists. It's a good point for roof joists as well 👍

[@bobbymooreok]

Can downlighting even be an option on a cold roof? Surely, the gaps and heat inside the insulation is a no-go.

[@JamieBettison]

Hi Again Ali - loving the series so far... I am thinking about a 'green roof' for my build (also with a couple of PV panels) - done loads of research on roof types and think I am going with a cold roof and a slope of 1/50... that sound about right?

[@AliDymock]

Hi Jamie, I looked at a green roof, that sphagnum moss looks great and should stay green with our weather. It is of course an extra load for the roof timbers to bear and additional cost but would like to see someone do it. Slope sounds spot on for drainage

[@AliDymock]

Hi everyone, thanks for your patience! A lot of theory in this one so had to create a lot of slides. As before, if you tell me the span etc. for your garden room I'll help find the right joist depth for you 🙂 EDIT: I've now created a span table document you can download here: www.alidymock.com/resources/

[@herickpaiva8708]

Hey Ali, thanks for your videos man, I am following them all and I am planning to go DIY with my garden office! I am planning to build my garden office with concrete block walls. The garden office will be 8m x 6m in depth, could you tell me the right joists and spacing for this, or should I go with engineered ones? Thanks again

[@herickpaiva8708]

I think finding joists to cover this length is hard?

[@joshuaomalley972]

Hi Ali, excellent detailed videos. Looking forward to doing this in the spring. Have you any of this info in spreadsheet form or similar? Some sort of step by step written guide? Many thanks, Josh

[@timmade]

I am trying to work out the spec of my door header to span a 3.6m bifold door. Do you have any idea what I would need if I was using c24 timber?

[@AliDymock]

@@joshuaomalley972 Sorry for the delay in replying, just saw this. I have written more on the website but the idea was that videos are easier to understand than written form, don't you think?

[@HowToSandAFloor]

Could you screw the firring strips to the underside of the roof joists and just stop them at the front wall so you don’t have a wider facia?

[@AliDymock]

hmm it's a smart idea, you'd have to fasten the firing to the joists first to stand any chance of working I reckon

[@1garrytaylor]

So I have been swayed to go for sloped joists so I can have a warm roof and not have to add the added depth of firing strips... What did you do about the angle on your front and back walls? the joists surely only rest on part of the walls as the top plates will be square? Hope you can help me! thanks :-)

[@AliDymock]

Well I think it's a good idea especially when you are building under PD! Very good question. I didn't do anything about as the angle was so slight and the angle brackets help distribute the weight and stabilise the joists, however if you want to do it properly you can cut what's called a 'bird's mouth' - one to google Garry!

[@alexox]

Love the series. It's helped me a tremendous amount. Currently just finished the floor. I have a question about the long walls (not the rake walls). How do your ceiling beams sit flat on the top plates? Did you cut the ceiling joists or do your top plates match the pitch of the roof? Or is it such a slight angle that it not something you have to consider?

[@AliDymock]

I think we answered this on email Alex but for everyone else: mine aren't cut and so lift off the top plate slightly which is fine because the angle brackets do the job nicely but on a steeper roof you would want to cut 'birds mouths' which I will eventually get to.

[@honumoorea873]

Ho man, you can have a cold roof without thermal bridges, not more then on a warm roof, you extend the "warm" and "cold" roof design too far, the under structure can be the same. The only difference is that a cold roof got a ventilation underneath the last layer that will allow condensation to dry whereas the warm roof can't... dry, which mean the vapor barrier got to be perfectly sealed (on a warm roof near impossible to do) I got a cold roof and i got an insulation layer that break all thermal bridges. In your drawings, you could add a layer of air then a layer of metal sheets over your warm roof... And it would become a cold roof.

[@AliDymock]

I'm afraid you lost me there! Do you mean insulation under the joists with a cold roof? Then yes that helps a lot but in turn you lose ceiling height.

[@honumoorea873]

@@AliDymock Hello, i meant insulation over the joist then a layer of air then a metal roof for example, this would be a cold roof.. No thermal bridges. The definition of cold or warm roof is just the fact that the cold one got a ventilated air gap under the last layer (can be shingles, metal roof, ceramic tiles)

[@AliDymock]

@@honumoorea873 Ah right, I thought the cold and warm referred to the deck above the joists and whether it was above or below the insulation and hence warm or cold!

[@dominicdale2873]

Do the roof joists need to rest above the wall joists? If so, did you not stick to the 16" spacing between roof joists when you got to each side and needed it to line up with the second stud in?

[@AliDymock]

Hi Dominic, well observed! Yes all joists are directly above the studs so the spacing changes at the ends

[@dominicdale2873]

@@AliDymock Thanks, want to make sure I get all details of my design right before building :)

[@dominicdale2873]

@@AliDymock Another question: How large are your overhangs at the sides and front? In CAD at the moment I have 600mm at the front and 300mm everywhere else though this may be a little large. Thanks, and looking forward to your next video!

[@user-ch1iy9hf5j]

Fantastic set of videos, I've been looking for something just like this for ages. Can't wait for the next updates!

[@AliDymock]

Thanks Neil! I'll be working on the warm roof vid this weekend 👍

[@loadsamonkeys]

What would be the problem with putting insulation between the roof joists but tight underneath the deck? You would then have no air between the deck and the insulation, so does that rule out interstitial condensation? Could condensation on the underside of the insulation then become an issue?

[@AliDymock]

Hi Richard, it's a good question and one I've struggled to get my head around. But basically if you have a vapour barrier below the joists which has zero gaps it will help greatly but chances are that vapour will still get above the insulation (even if there is no space between the insulation and the deck). It will condense and get trapped and cause rot etc. Have a read up about cold roofs, every article says that ventilation is required which means an opening on the front and back of the building to allow movement of air for vapour to escape. I guess it comes down to how long you want your garden room to last. There won't be any condensation under the insulation as the air will be warm. I hope that helps a little bit.

[@loadsamonkeys]

Yep, I think you're right, I could see that happening. Really goods vids by the way, starting my build this weekend, weather permitting, and am taking a lot of your advice!

[@AliDymock]

Exciting, good luck with it! There are plenty of different ways of building a garden room, mine is quite over engineered compared to some I see on youtube, but hey, it makes me happy

[@stevebeard9656]

Hi , Just come across your video. Did you get the roof joist from a normal timber merchant ?? I am building myself a new workshop and have decided on a 5m width. I was going to use 4x2 as joists but am now thinking they may not be strong enough. The roof will be sloped and insulated with 40mm celotex. Any advice would be great

[@AliDymock]

Yes, from Builder Depot who are very good if you're in the South East. Just look at a few timber merchants for prices. Selco are okay, Wickes are very expensive and B&Q don't often stock a lot. 4x2 simply won't be strong enough, you could undersize them slightly from the span tables, - I don't think you'd fall through but may see sagging over time. Go with the right size. For my 4.8m span, I needed 220mm x 45mm

[@stevebeard9656]

@@AliDymock Thanks mate. Since i commented i have decided to cut the width down to 4.5m due to finding the timbers long enough. It will be 7m long and on a concrete base

[@philhode5104]

Sorry I missed,how did you achieve slope on roof,front wall shorter?

[@AliDymock]

The back wall is shorter than the front so the joists themselves slope but you can build the wall level with one another and then use firring strips instead. I recommend going for at least 1:40 slope in retrospect. So take your span in cm, divide by 40 and that's how much lower the back wall should be or how thick the firring strips should be at the front.👍

[@philhode5104]

@@AliDymock thank you,building a conservatory soon, joined obviously to house

[@Goorney]

The question of whether or not to use sloped joists is an interesting one. I'm currently building a garage and using CAD will help provide me with accurate dimensions when cutting the studs.

[@mar4elo999]

You know what mate, I ve been waiting for the builder to finish the roof for ages and you inspired my to finish it myself, I am just gonna do it!

[@AliDymock]

Do it!! A flat roof really isn't that tricky 👍

[@andypowlesland599]

@@AliDymock any more projects on the go?

[@AliDymock]

@@andypowlesland599 Yeh! Moved house, made a potting table (2 vids out on those) and a side gate (vid to come on that) and now doing fencing before re-doing the roof of my garage! Busy!

[@andypowlesland599]

Ali Dymock thats great! I’m a landscaper who takes on similar jobs! Just about to build a 12x12 t and g shed that is fully insulated and able to break down to 8x4 sections for transporting when we move in a couple of years!

[@AliDymock]

@@andypowlesland599 Nice!

[@Badgerworkshop]

Really useful information. Thank you

[@stephenwright8476]

Hi Ali, what are your thoughts on the birds mouth cutting on the roof beams? i’m about to start my roof but unsure if they are required or even actually needed

[@AliDymock]

So I didn't bother because the slope was so slight but technically the weight of of each joist (and roof) rests on the inside edge of my front wall and outside edge of the back but the angle brackets make it all solid. So yeh go for it if you have a steeper slope/can be bothered but not a problem if you don't. Have a read of the Q&A here: www.alidymock.com/nick-somerville/

[@stephenwright8476]

Ali Dymock thanks Ali, plenty of pics taken through the build to send over once done 👍🏻.

[@AliDymock]

Excellent, good man 👍

[@alasdairmackenzie515]

This couldn't be better timing! Thanks to Keith Brown for putting me onto your series of vids. I'm in the throes of planning an extension to my own 12' X 10' shed. Going to add - subject to planning (I live in a conservation village in the North West of Scotland) - another 8 feet (20' X 10'). Your vids have been very, very helpful. Thank you so much. Hope the rest of the build goes well. Best aye!!

[@AliDymock]

It was very kind of Keith to give me a mention, glad the info is helping you out. Always good to have another Alistair/Alasdair on board, thought 'Ali' would be easier for people to remember though! 😁

[@alasdairmackenzie515]

Yup. As one Ali to another, I've been called many things... I really admire what Keith's doing too. It's a very helpful community. Cheers!!

[@michaelg124]

As an audio technician, i want to thank u for the upgrade in your gear!!

[@AliDymock]

Haha I went from a blue snowball to Samsun q2u with audacity. Feel free to email me any recommendations for better sound 😊!

[@Hawksmere]

Nice! I need 5.8m joists. Can i use the, as singular joists like you have? Or shall I double them up?

[@Hawksmere]

Hi mate, see you didn’t use jiffy hangers. Has the brackets held it all down with no twists?

[@paulfearns7132]

Hi Ali again very impressed with the way your build is progressing i understand the options you had with the pitch of your flat roof and the best way to go about it off course using firring strips would have been a lot easier and less time regarding labour and working out but in the end i think going with the option you did was the best way to go giving your fascia boards a uniformed look around the building i also liked how you used the angle brackets and twist nails again instead of just cheek nail and screwing your joists also giving the joists a more solid fixing especially on your overhangs and loved your top tip with screwing temp timber hangers to sit your fascia boards onto for you to get your first few fixings in place a great tip for people doing this kind of work on there own as always massive thumbs up :)

[@triumfdula8830]

Can anyone give an answer, making a horizontal roof with 5 x 30 cm wood boards / joists (30 cm being vertically) would the boards in 5 meters length bend from it's own weight and snow ? And what is the max spacing allowed between boards, is 70 cm enough ?

[@MrDenisJoshua]

I like a lot the songs you use, but the link is not work anymore. Can you let me know the names please ? Thanks a lot

[@AliDymock]

soundcloud.com/search?q=dj%20quads

[@MrDenisJoshua]

@@AliDymock Thanks a lot... I'll put it into my phone :-)

[@mudbone32]

Amazing. This is exactly what I'm doing over the coming weeks and without your videos I would almost certainly have fucked it up. Feeling much more confident about it now thanks :D

[@AliDymock]

Great stuff Dan!

[@Direct_and_Honoust]

Just subscribed, you changed my mind in going for a warm roof instead of the cold one, maybe it past my eyes, you talked about it in your vid that the roof has a slight angle in order to get rid of the water, however your frame looks very straight on the walls, how did you create the slight angle?

[@wynneconnolly2729]

Music was terrible...I had to turn sound down then rewind to hear what I missed when he began talking again. Would have preferred a talk over instead of trying to read and watch while being distracted by shitty music.

[@eltelturbo]

How much slope did you put on your roof? I'm using reclaimed timber for the corner posts and base frame. Corner posts are 4.5x5 inch and base frame wood is 3.75 x 4.5 inch. Room will be 2.6 x 3.2m footprint. Will I be OK using this wood after painting with sikagard wood preserve? Everyone says wood touching the floor must be pressure treated. Thanks

[@Jim-yp8sh]

Great videos Ali. I wonder if you could offer some advice. I’m planning building a 3.5m x 3m garden room. As I want to keep the max roof height below 2.5m, what size floor and roof joists would you recommend at 400 spacings? I’m thinking 4x2s for the floor and 5x2s for the roof. Would this be sufficient?

[@jakemarshall300]

Hi mate, thanks for these videos they are spot on! I have a question.... what would you recommend to use in terms of joists sizes/ spans for a roof sized 5.64m x 5.68m as looking online its 63mm x 220mm but seems excessive,. Also - the cold roof design, what dead load per square meter should be used? Cheers!

[@Jaaammmbbbooo]

So between the plasterboard and underside of vapour barrier is just air? Does this space have a vent in the fascia or is it completely sealed? I am planning this for a replacement small extension flat roof. Cheers

[@AliDymock]

Yeh that's right, between the roof joists it's just air. No need to vent as the air in that space is warm so no condensation will occur. With a cold roof you do need to vent through the soffit or facia. 👍

[@peterknight7880]

Just a thought. A structural engineer might charge you £50-£100 to check your joist sizes. If you could have gone down even from 220mm to 195mm joists, that would have been worth it in material savings, not to mention the benefits of manhandling smaller timbers.

[@agw1996]

Ali i am building a garden room with a shed area at the rear of the building. The floor space is 4.8m x 4.0m with a stud partition for the shed area at 1.8m making the garden room area 3.0m x 4.0m. I note you used 45 x 220mm for your 4.8m span. Would the same be appropriate for my build or can the size be reduced given the support of the stud partition? Many thanks in advance of your help.

[@AliDymock]

I'd go with 6x2"s at 400mm centres over the 3m span personally. You could move them out to 600mm spacings if that suited the rest of your build.

[@chazred131]

Hi Ali, appreciate all the work you’ve done with the videos!! I’ve got a question on my build. It’s not square and the roof spans from 2.5m one side to 4m the other, I was going to use double 6x2 but is this an over kill? I’ll maybe need it on the first 2/3 rows of roof joist on the long side but then seems unnecessary to do it the whole way? Or do I need to keep it standard through the whole roof? Any help you’d be able to give would be great full

[@darrendouglas3334]

Hi Ali. I'm building a warm roof garden room but due to the fact there is an overhang on the sides this means using full sheets of OSB on the roof means I either have to cut short the OSB (if joists and wall studs line up) or don't worry about lining up the joists with the wall studds. I can see from your video that you haven secured OSB to the edges of the overhang but your joists and studs line up, so did you have to cut some off your full OSB boards?

[@squeekhobby4571]

Just brilliant and too detailed. Searching for similar content and found it

[@iaindonald8327]

Could you help me with my plans, if I can only find 8x2 timbers at 4.8m lengths how can I build a rod for a 5m2 summerhouse with an over hang??? 🤞🏼

[@iaindonald8327]

Roof not rod

[@jojitsu56]

Awesome video, really appreciate it. Could you be so kind as to tell me the timber joist sizes needed for a 6.2m span at either 400 or 600cm centres? Many thanks in advance

[@twwanderer]

Stunning build, you should be proud of yourself for it (and doing it solo). Love the theory bits and explaining it all really clearly.

[@AliDymock]

Thanks Alex, much appreciated. I guess I am sort of proud, but will be especially so when it's complete and so is this series. Some way to go with each!

[@xaaviercito1]

I’m about to do mine, but I will install 2oz fiberglass mat on top. That will help a lot.

[@PaulClarkson77]

If you use firring strips how do you deal with the gable ladders? They'd be fixed level with the top of the strip, which would be higher than the front fascia and wall head.

[@PaulClarkson77]

And 2 minutes after posting I realise you fit the ladder as normal and a firring strip on the outside rafter😖

[@rayhurt714]

Great videos thank you, A question please did you not have to cut a birdmouth in the roofing joist so that they sat completely flat on the top of the wall plates please? Also what was the diffrence in height between the front and back walls to create the right slop please.

[@locksafesecurityservices8117]

Great video converting my garage can I connect 2x6 to the existing wall by creating a wall plate . Also when you when for a sloped roof internally one side was higher then the other ?

[@neate3133]

I am loving your videos and currently starting out on the adventure of building a gym in my garden. Would it be possible to get a list of all the materials and equipment you use. You truly know more than most of the builders I’ve spoken to about my project

[@ThomasKempDesign]

Any reason you couldn’t put the firring strips under the joists and cut them flush to the walls? You’d get the benefit of a thinner roof and flat underside without the need for the hassle of the taller wall.

[@simonharwood5780]

Really good! Thanks for taking the time to film edit and post. Very useful

[@AliDymock]

thanks Simon!

[@eversleyowl]

Found this series yesterday and now binge watching, very interesting, informative and well made videos, thank you for making them. I do have one question having watched this video. In an early episode I believe you said you were building up to the boundary, but you have now created an overhang on the side of the building, does this overhang the neighbouring garden? Not a problem while you live next door to your mum, but...

[@b21playa]

Excellent. Shows how much it,beer prices have gone up, 6x2 is £30 for 4.8m 🙈

[@AliDymock]

I know, it's mental isn't it!

[@beardedpianist]

I'm interested in your roof joists and boards. I'm in the design phase of building a studio for my garden and I'd like to know if your outside 'overhang' joists are in keeping with the 400mm centres of the rest. Did you board over the overhangs? If so, did you need to cut every OSB board that sat on the overhang?

[@AliDymock]

Hi Michael, the joists just continue over the top plate to create the overhangs. I board over the whole lot in Part 10, worth checking out.

[@alexramsay8904]

An invaluable series of videos, many thanks! A slightly confused question re firring strips - I'm guessing they should also be laid on top of the side pieces so the overhang is fully supported right to the edge - in which case the fascia boards at each side will need to be wider (deeper) than the joists, presumably?

[@mariafhp]

Thank you for this video Ali . I am self building garden shed alone and was struggling with how to keep the long facia board in place , screwing a bit of wood at each end is great . 🤗

[@vonjournet]

So when laying the rafters on roof you don't need to cut birds mouth on the boards you can just use brackets

[@JoeGP]

subbed, glad to see you finally got the voiceover audio levels right.

[@AliDymock]

Got there in the end ehy. It’s just not that easy on iMovie for some reason.

[@ipfishing1466]

Caberdek flooring would have been a better choice it keeps dry with protective covering. Good work though

[@AliDymock]

Interesting, I've not come across that product before, cheers

[@tyler4164]

Loving the videos so far. Gonna be starting my own workshop build very soon. Smaller then yours around 2.4m x 4.8m & 2.5m high. Havnt got room or money for a build quite like yours but should be ok for me

[@AliDymock]

Excellent, that sounds like a pretty good size to me!

[@tyler4164]

Ali Dymock its ok. I would of gone bigger & had less garden but the wife wasnt happy with that idea so i compromised. Happy wife happy life!

[@ELPANDAP]

Can we use that same roof and make a deck on top or I need to add beams ? And more ?

[@Thenewgards]

Of all the videos on building a shed, yours is the best one. I

[@nickrudden4366]

Thanks for these videos! Do you need to account for the gap between the roof joists and the top plate on the front and back walls (caused by being a different height) or is it too insignificant to matter?

[@zip7806]

2:57 He is saying "Beaks in the insulation" not Bricks.

[@WeChooseAdventure]

Could you tell me how how much of an overhang you had at the side of the building ?

[@joeyj6526]

Where was it you got your 6 meter joists from? Is it covered in another video?

[@arthurfowler5943]

Hi Ali, great videos. A big help. I have a quick question... did you ever consider double joisting the roof joists? the way I understand it is it adds 25% span to the single joist figure? Im thinking its a way to get the roof depth thinner for longer spans. I have the same depth planned as you and if I double up 47x170 timber, I should increase the span from 3.808m to 4.76m, thus saving 50mm in roof frame depth. Would appreciate your thoughts if you have time, many thanks

[@AliDymock]

Since doing mine, I have and would like to make a video on it and potentially reducing the spacings as an and/or. I try to think of all circumstances when I make these videos but because I had planning permission for 3m height wasn't such a worry so 2x9s didn't impact my ceiling height. Do you have a link to that 25% additional span for doubling up, I'd be very keen to see.

[@michalmalinowski9867]

What size are your rafters? I will be doing garden room with span of 5m, just in doubt 8x2 timber at 400cc will be enough for my project. Roof will be covered with 12 mm sheathing + felt on a top of it. Thanks for any advice

[@AliDymock]

9x2" (220 x 47mm) for mine. 8x2" will be perfectly fine, go for it judging by span tables.

[@zafg2505]

Hi mate, what size is this gardenroom? Cheers

[@threepennypirate8529]

Great series. Thank you so much. Dumb question but Can I put the firing strips under the joists?

[@tabathv1]

As I understand it , from various sources including some canadian, OSB can at as a vapour barrier so technically you didn't need the polythene? Also I've seen warm roofs topped with EPDM straight on top of the PIR, whats the advantage of putting the extra layer of osb on?

[@AliDymock]

Hi, I've never heard of OSB acting as a vapour barrier. Besides, there are gaps between sheets so definitely wouldn't work. Regarding EPDM straight on PIR - I've seen it done but given how walking on PIR will crush it somewhat I wouldn't recommend it myself.

[@JohnPalmerUK]

Nice videos Ali. These are very well made videos and I like the Lofi Chill Step interludes. Enjoyed it and took 2 pages of notes. I'm building a similar sized room as your garden room. But I'm going to be brave and attempt an L shape keeping it under 30m2.

[@AliDymock]

Hi John, thank you. You're the first to mention the music! I think I've sorted out the sound levels now so hopefully they add a bit of fun to the videos and something to look forward to after all the info! Sounds like a good project. Feel free to ask any questions and thanks for subscribing

[@ScottNicholson1973]

Hi Ali, another couple of questions if you don't mind re the roof overhang - it looks like you cut the ends of the roof joists square, which suggests they'll be at a slight angle at each end, rather than perpendicular to the ground, which then affects the soffits/fascia similarly. Has that worked out okay for you or did you make an adjustment? Also, going back to the maximum 3m height plan, did you base that on the highest part of the roof, i.e. the overhanging extended bit at the front? Thanks - looking forward to seeing the next part!

[@AliDymock]

Sorry for the delay Scott, youtube thought your comment was spam for some reason so I had to approve it first. You're right, I cut them square. The slope is so minor at 1 degree that it wasn't worth messing about. Have a look at 9:09 in the video which is a sneak peak - you really can't notice the slope, nor do the fascias look anything other than vertical (at the front) and it doesn't bother me at all. The slope is so gradual I didn't even need to cut birds mouths for where they sat on the walls. I'm not sure what you mean about the soffit, cutting them square or not won't affect them I don't think. Yes the maximum height (in my case 3m) refers to the highest point on the building - my front fascias. However, as someone pointed out in another comment, it's not necessarily calculated from the ground directly under my fascia but from the highest point around the garden room. For example on my mum's side, the height is about 3.2m but at . the back just 2.9m as the ground is higher there so that's fine. The chances of an planning officer coming round are slim so don't worry too much (famous last words!).

[@jrutter9013]

Hi Ali, I am building an extension to my kitchen. It is made mostly from I beams both vertical and horizontal. The roof will also include two roof lights and a chimney for a wood burning stove which will hang in mid air. The downpipes will be part way back along the sides of the extension so I will have to assemble the firrings front to back and back to front to allow the fall to meet in the middle. I have I beams running around the perimeter of the roof. Have you any links to this type of design as I plan to do this work myself as the quotes I have received have been crazy. Regards John

[@AliDymock]

Hi John, I'm afraid I don't as yet. Sounds like a good project and hearing from people looking at these videos planning on doing extensions it's made me want to go do one now!

[@nazamosey1646]

These Videos are Incredible .Seriously. It's very technical , informative and educational. Hate looking at Actors all the time with their make up. These type of videos are 100% Perfect. Best video on YT by far. As a learner I can now attempt my new roof

[@AliDymock]

heheh, glad you like them Naz!

[@ryanbritton804]

very nice job well done I'm building one at the moment but going to use rock wall as its much cheaper just going to finish the roof completely first then windows and doors and then put 18mm moister resistant chip board floor in after words and insulate it top to bottom afterword's. also if you counter batten the ceiling joist you get all your cross flow and ventilation very easily it saves thousands of pounds, as you can use loft roll insulation and no planning required as you will only be 2.5 meters max. I'm estimating 7 grand in total its 7m by 5m with a glass fibre roof and I'm using reclaimed windows and doors.

[@AliDymock]

Sounds great Ryan. I can say that mine is crazy warm so I think rockwool is a great option 👍

[@tomharries847]

Hi, firstly you have done an amazing set of videos all of which i would of done exactly the same way as what you have done. i enjoy watching the american framing videos. i am going to build my own workshop/shed at 12ft x 10ft with insulation, electrics etc. i went to wickes today to get a rough idea on price for materials. if you dont mind, can i ask what this whole build cost? many thanks.

[@AliDymock]

Hey Tom, good on you for building your own. 1. Don't buy the majority of stuff from Wickes, use a builders merchant, it's cheaper. 2. I'm not sure yet but try to answer the question here: www.alidymock.com/start-here

[@vikingofengland]

Once again, top work and well though out. Been planning my man cave build for ages and you once again have validated a lot of decisions I have made. I am the same as you, not a builder and this will be the first time I have ever done a build like this.

[@MrJonpac]

How did you get on. Did you build it

[@vikingofengland]

@@MrJonpac yep all built 👍🏻

[@MrJonpac]

@@vikingofengland Nice one. Just doing mine now . I've copied it exactly . Great videos

[@michaelburton3535]

Thanks for the explanation Ali, it's really helpful as I'm building a home office atm for a client.

[@BlueGamerDude]

2:11 some isulation are cut before hand to fit between joists of 600mm apart

[@AliDymock]

True.

[@lightning3a]

hi Ali the span of my garden room is 3.04m x 3.96m I thought 47mm x 170 would ok for roof joists? what do you think? cheers Angelo

[@AliDymock]

Hi Angelo, I'll presume the joists will be going across the 3.04 span so if you go for C24 timber and space them at 400mm/16" apart you could use 47 x 145mm (2x6s) very comfortably but if you go bigger it won't hurt of course but may cost a touch more and leave you with an inch less ceiling height.

[@reyman202000]

Very informative. I’m planning to build

[@kave999]

Ali - question for you. Are sloped joists something I can buy or did you raise one side with wood for the run off? How did you notch the joists to make sure they were flat against the framing timber?

[@AliDymock]

Hi Kieran, you can buy firring strips that have that taper on them but often they are not long enough, they weren't for my build, so in that case you need to cut your own. If you go the other route and have different height walls then if the slope is quite significant you will need to cut 'bird mouths' in the joists. For mine at a 1% slope, I didn't bother.

[@petergreen7594]

With the over hang on the sides would it not have been better to leave the last full joist out each side so the small peices of joist were longer and had more of a canter liver to them? Fantastic series BTW I'm really learning a lot and is really helping me with my build I'm just starting Thank you

[@AliDymock]

It's a good idea and shows a good thought process. For. larger overhangs I'd say that is the better/only way but the downside is upsetting the joist spacing for plaster-boarding and OSB on the roof/ceiling so for similar or smaller overhangs to mine I'd say you're better off doing what I did.

[@adamcollett4080]

Hi Ali, Loving the videos and been a massive help! Just started my big build and have a question for the rafters. As they are on an angle, did you cut the face end of the timber so it was still vertical, or leave it at a slight angle?

[@sofie9180]

This video is awesome, could not find the span tables anywhere online! Don't suppose you know anything about removing rafters in a flat roof for roof lantern installation?

[@AliDymock]

Yeh the span tables were more freely available when I started out, I can’t find them anywhere now either. I know a thing or two, best to email me so I can send a couple of photos :) [e-mail]

[@chrisoxley3617]

Excellent video. How did you get the rafters flush on the wall plates, and still manage to maintain a slope/pitch? Could not see that anywhere in the video

[@AliDymock]

You would do something called a 'birds mouth' which I skipped and just made sure they were connected really well with angle brackets. If I were doing it again I'd use upside down joist hangers. Birds mouths are nice but a little tricky for first time DIYers

[@marshal487]

Thanks , this video help me a lot 😊😉🙏

[@username2703]

Nice video bro

[@clivevassell2064]

Hi I have learned a lot from your videos, great information. But how is your roof rafters sitting on the slope walls without cutting bird mouths. Once again Thanks

[@AliDymock]

So the slope is so little I couldn't see the point. They do technically sit on the inside edge of the front wall and outside edge of the back wall but the angle brackets keep them very secure. You could cut birds mouths and for steeper roofs I've recommend doing so. In fact I have a garage roof that I'll need to do it on. There are videos on birds mouths with some crazy calculations but I reckon it can be done quite easily if you apply a bit of common sense 🙂

[@clivevassell2064]

Thanks, I’ve always wandered how, now I can start my project feeling more confident. Keep up the good work.👍🏾

[@locksafesecurityservices8117]

Great video converting my garage can I connect 2x6 to the existing wall by creating a wall plate . Also when you when for a sloped roof internally one side was higher then the other ?

[@AliDymock]

yeh that's right. If you have brick or block walls you'd cement a timber top plate and then use L-brackets (long type -can't remember the name to secure it to the inside wall. Then you attach the joists to the top plate. As for the slope, that's right, I have a sloped ceiling - it looks kinda cool.