Amateur ambitious build. Ransoman builds a Studio. (Shed)

[Ransoman]

Hello all,

I have very limited woodworking experience and this is my first ambitious build so please be gentle (hammer). Fortunately I have a fair selection of tools at my disposal.

The Breif:
My Girlfriend is a recently graduated professional artist and as she specialises in large works, her existing studio (a 4mx2.5m flatpack log cabin) just wasn't big enough. To get something big enough we would be looking at upwards of £5k so we decided to self build something with a budget of £2k.

We decided 6m by 4meters with a single sloping roof with 3m at the highest point would be the ideal size however after drawing up some rough plans and working out the wood sizes we dramatically reduced the cost by opting for 20' by 14' with a 9' high wall and 7' low wall.

The reason I am going between metric and imperial scales is because B&Q, where I did my original material specs, sell their wood in 1220mm by 2440mm (or 8' by 4') so I did my plans in Imperial. Unfortunately the wood I ordered from a local timber merchant was sold in imperial sizes and all boards were too small As you can imagine, this caused great frustration when I discovered this AFTER I had built a perfect base to 16" joist centers.

The spec:
The foundation is a pier style foundation (as the area is prone to flooding and close to large trees and consists of 15 100mm by 100mm posts sunk 40cm into the ground and set in post crete, topped up to ground level with Mastercrete. the posts are layed out in 3 rows of 5 along the longest dimension of the shed and each row supports a 20' 94mmx100mm "Skid". Damp is controlled via a piece of Damp proof course at the top of each post and a membrane sheet on the ground.

The base is 20' by 14' (6.1m by 4.27m) and constructed using 47mm 100mm c16 with joists at 16" spacing. Insulated with Knauf rockwool supported by a "Hammock" of roofing membrane and capped with a damp proof membrane. The floor itself is 18mm OSB3.

The walls use the same 47mm by 100mm c16 timber and are at 600mm spacing (at this stage I discovered my error with the wood and adjusted the joist spacing to compensate). These will be cladded in 9mm OSB3 on the outside, Wrapped in roofing membrane, then battoned and finally clad in whatever we can lay our hands on at a reasonable price.

The roof is again 47mm by 100mm c16 at 400mm spacing, topped with 12mm OSB3 and will have a 3 layer felt roof. I have yet to work out the angles but it it drops 600mm over 4270mm. One concern is that I may have underspecced the roof joists but it will be "Noggined" for re-inforcment and an additional support beam can be installed later if needed.

So, Big mistakes? Apart from the Imperial design - Metric materials problem, the only other real mistake was not measuring and marking the foundation properly so the rear row of posts were miles out resulting in 2 having to be moved.

I have attached pics of the progress so far. At the time of writing, the base is perfectly square and perfectly level, All 4 walls are standing and I am more than half way through installing the noggins. The whole structure is very rigid and sturdy. I am very happy with it so far but we are almost at our budget already :shock: - At least we have bought all materials although I have run short of c16!

Current build stats:
Days of work: 11
Screws used: 450+
Blood injuries: 2 (OSB splinters!)
Cups of tea/coffee consumed: lost count
Costs: £1600

 

[Adam9453]

For a 4 metre span with a shallow pitch, the roof timbers should be at least 8x2's at 600mm centre's. The roof beams should be ideally mounted directly over your vertical studs in the walls. If you use smaller timbers I'd be concerned whether it will take the weight of a lot of snow resting on it!

 

[=Adam=]

This looks excellent!

My only concern is the choice of timber for the roof members. I did calculations today for a garage build. The span was 3.5m and 50x150's would work at 400c/c. Now in all honesty, 100mm timbers may well work, but the overall deflection would be greater than that allowed in the British standards.

Without doing the exact calculations, I would estimate that you would need 50x200 c24's at 400c/c (possibly 600, but we don't tend to recommend that large of a joist spacing.

If you would like any more info, or for me to run the calcs then please get in touch.

Thanks

 

[Adam9453]

This looks excellent!

My only concern is the choice of timber for the roof members. I did calculations today for a garage build. The span was 3.5m and 50x150's would work at 400c/c. Now in all honesty, 100mm timbers may well work, but the overall deflection would be greater than that allowed in the British standards.

Without doing the exact calculations, I would estimate that you would need 50x200 c24's at 400c/c (possibly 600, but we don't tend to recommend that large of a joist spacing.

If you would like any more info, or for me to run the calcs then please get in touch.

Thanks

He's only using felt to cover the roof so 8x2's at 600 centres are sufficient.

 

[tomf]

Looks a very usable size!
Personally I would not have done the foundations like that, I would done used pad stones, >700mm 300x300mm hole and filled it with concrete then block work up to floor joist level. The wooden posts will be the weakest point as they will rot and might sink at only 400mm depth however having saying that, there won't be too much weight in there and I do tend to over complicate things.

 

[Ransoman]

Thanks for the comments everyone. All feedback is appreciated.

The roof joist sizing has been bugging me for a while so I am glad to hear from those vastly more qualified than me on the issue. I have just sent off a message to my timber supplier for 8x2's and Will redesign the roof at 600mm centers instead. Snow is very much an issue up here and I can't ignore it. Thanks Adam and Adam9453 for advising this.

Tomf, The posts rest on a clay layer on the ground and are tanalised. The cut ends have been re-treated so I am hoping rot won't be an issue. To further avoid any movement the posts will have screws drawn partly in and then cemented over. I am designing this to last 10 years so I hope this will be sufficient.

 

[tomf]

The posts rest on a clay layer on the ground and are tanalised.

Firstly take this only as constructive I am no way wanting to put anyone down, this is just my thought process. Clay is actually the worst type of substrate as it will not let the water drain out of the post and can shrink/swell massively. You may find rot sets in where the top of the concrete meets the post. Tanalised timber comes in many different classes class 4/5 being in contact with the ground, even with class 4/5 I would use 1-2inch of pea gravel so it's free draining.

If you can go for a warm roof it is a lot easier as you don't have to worry about ventilation. You can get seconds torch on ready rigid insulation for quite cheep if you keep yous eyes on ebay but it'll be more expensive than fiber glass between joists. If not i would counter baton so you dont need to vent all joists.

 

[Paul200]

Excellent project! Especially as I've been making plans for something very similar :wink:

My concern would be the floor insulation. Is the 'rockwool in a hammock' method typical for suspended floors? Has anyone any experience of using rockwool like this? I only ask because I live in splendid isolation on the edge of a wood full of rodents (among other things) and wondered whether an OSB 'sandwich' with rockwool between would make it more rodent-proof.

Presumably mice and the like will cause problems whatever you do to keep them out but I just wondered what others think.

I'll be watching this thread with interest. Thanks for posting Ransoman.

 

[SammyQ]

You might want to think about editing the fifth picture's caption? Just sayin'.....

Sam

 

[Ransoman]

Thanks again for the comments and advise.

Tomf, Thanks for pointing that out. I will do a regular inspection on the posts to ensure nothing happens. If worst comes to worst and they start rotting or moving excessivly it wouldn't be impossible to replace the posts one by one with brick pillars or similar.

Paul200, the idea for this was from the good old readers digest DIY manual for insulating floors. I used the builders paper "Hammock" rather than chicken wire/garden net as I had read elsewhere that it was a suitable alternative and is relativly cheap It was also easier to handle. The ultimate plan is to enclose the foundation in the same way you would a static caravan (ventilated of course. so no rodents should be able to get in there.

SammyQ, well spotted haha, oops.

Only update to report is the 2x8's are now on order. This weekend I will be building up the gable ends of the sloping roof and installing the last of the noggins on the walls.

 

[skronk]

Hope you have it well tied down Ransoman....your wind will be the equivalent of here on Skye. Take off time ! :shock:

Looking well though. Good luck.

 

[Paul200]

The ultimate plan is to enclose the foundation in the same way you would a static caravan (ventilated of course. so no rodents should be able to get in there.

Now that's a good plan. Hadn't really thought much further than getting a cat, to be honest

 

[Shultzy]

If you look at my workshop build there are a few tips on making the roof joists for a pent roof.

 

[Ransoman]

Thanks Shultzy, I will be sure to check that out.

Well this weekend was a disaster I finished the noggins which wasn't a problem, I then set about the "Gables" (not sure if that is the correct term for a sloping roof). I managed to work out that the roof angle is 8 degree's but I just couldn't get my brain in gear to assemble the end frames. When I was finally making some progress the temperature dropped, it started raining and then turned to snow and was a white out blizzard for the next 6 hours! The base is covered in a tarpauline and when I went out to check on it after the snow had stopped it was filled with water and had breached the tarpauline on the corners and at several points in the middle where it was leaking.

Fortunately I used OSB3 and the damp proof membrane should stop the insulation from getting wet, But i will still have to spend a lot of time drying it up today.

 

[Ransoman]

No new pics yet. I have the 8x2's and they have all been cut to size and I am in the slow process of notching them where they sit on the top of the walls.

The rain is doing its best to ruin the structure and some of the OSB3 has expanded slightly at the joins. it seems there is no such thing as a proper waterproof tarpauline. I reckon I am a few good days away from having it watertight.

 

[Ransoman]

Housten we have a problem.

So the build is progressing well albeit slowly due to my working on weekdays. I almost have the roof completed, Those 2"by 8" joists were an excellent suggestion!.

Unfortunately my Tarp that I use to protect the base is full of holes and is not coping with all the rain. the base has been soaked many times and the OSB is starting to puff up at some of the joins.

The main problem though is despite the thick Damp proof membrane between the floor joists and the OSB floorboards, some water has made it to the insulation below. I will have to remove the builders paper that is supporting the insulation and replace it with Battens.

Should this worry me? Only 2 joist spans on one side of the base got soaked and I had to cut a hole in the builders paper to drain the water out. It is my understanding that a bit of water won't do any harm as long as it drains away and dries out quickly but some of the OSB board edges don't seem to be drying out??

 

[Ransoman]

A couple more pics to show the current progress.

The 2 rearmost walls are almost completely clad using 150mm fencing timber in a board and batten fashion. Just got 15 or so boards to go up then I have to do the battens.

As you can see the roof is done (3 layers) and with the 2x8 joists it is solid as a rock with no flexing. although I have yet to trim the edges so it looks a little rough.

a few weeks ago we had some bad storms and the Studio remained bone dry on the inside and didn't move in the wind.

I will hopefully be putting in some windows this weekend as well as finishing the cladding on the plain walls.

 

[Paul200]

This is coming on well. I've started my build and had exactly the same problem with rainwater getting into my OSB floor. Blimmin pain. I considered ripping it all up at one point but then got sensible and decided to let it - hopefully - dry out and then maybe sand down the raised joints and, if that doesn't look too clever, lay another floor over the top once I've got a roof on.

Other people must have had this problem - is there a solution other than get all your mates round and get the roof on double quick? The only thing I can think of is to build your base with a double layer of timber around the outside and leave the floor until last.

Has yours dried out yet Ransoman?

Cheers

Paul

 

[Ransoman]

Almost Paul. There is a little water soaked into the end of just one board but putting down cat litter has been surprisingly effective. It draws the water out and into the litter.

If I was doing this again I would actually leave the floor uncovered so just bare joists , then fit the walls and not cover the floor untill the roof is in place. But in the grand scheme of things, no permanant damage has been done so I am not too bothered.

A few more details for those interested. The frameworks as mentioned is 47mmX100mm timber at 600mm spacing. This is covered in buiders paper which is then vertically battened over every stud, then counter battened every 600mm or so. This gives a 48mm air gap behind the cladding. The outer cladding is 150mm boards with a 10mm expansion gap between and 75mm battens covering the joins. The inside will be insulated with rockwool slabs, vapour barrier and then 9mm OSB3 but I have not yet decided if I will/need to put in another air gap.

 

[Ransoman]

A few recent pictures. It is getting there and looking pretty damn classy.

The windows are now all done. The windows were salvaged so the studwork had to be modified to accomodate them. The 3 small side by side windows on the side image had a 4x4 lintle installed above to cut the 2 studs out completely.

As of now the cladding is 60% done. I just have a little above the main door and front windows to do, then the battens need to be cut and nailed onto all of the board gaps. Once that is done I just need to make the door, then insulate and line the inside, then it is finished!