Another newbie needing some shed-building advice

[stephenmg]

Hello all,

I've been lurking here for quite some time and very much enjoyed reading about the fabulous projects that are discussed here. I am neither skilled nor experienced enough to be able to contribute much I'm afraid so have never posted before. I've got a project of my own planned now though so have come somewhere I can trust for advice!

We moved into our house a couple of years ago and in the garden is a 14' x 10' shed put up by the previous owners. Nothing special, just a bog-standard, flat-packed shed of the sort that I could get into with a nail-file in about 2 minutes flat! It has a 3" x 2" framework clad with 19mm shiplap - some of which has shrunk so gaps are starting to appear. I have a restoration project I want to house in there so decided to beef it up a bit. However, having given it a good look over I decided it would be easier to start from scratch!

My budget is pretty minimal frankly so I plan to dismantle the existing shed and re-use what timber I can - mainly the 3" x 2" framing. The base is reasonably sturdy so I'll re-use that, extended slightly lengthwise, for the new one.

So here's the plan and a couple of questions I'd be grateful for advice on.

The Base
The existing shed base is good and solid and is made of a number of 3" x 2" timber joists covered with 1" thick sawn timber planks for the floor. This sits on a well-laid, level base of flag stones. I plan to use this base as it is but will add a few more joist to beef it up further and will paint the bottom with bitumen paint to add extra protection. Once built I may cover the floor internally with chipboard for extra strength.

Question 1 - would it be wise to add some sort of waterproof membrane between the joists and the flag stones or will the bitumen paint be enough?

The Walls
To save money I plan to re-use the 3" x 2" timber from the existing shed for the new one, then clad it in tanelised 27mm loglap. I've secured the required loglap at a very good price - this is the bulk of the cost of the project so I've had to get what I can for the cheapest price. That means I've had to compromise on the available lengths which are a mix of 3m and 4m rather than the 5m lengths which would allow me to clad the length of the shed in one go. I'll therefore need to arrange a frame member at the appropriate metre multiple to coincide with the cladding joint.

Question 2 - to be as economical as possible with timber, and to work with the round metre lengths of loglap, I'm considering positioning a vertical frame member every 1m (plus a healthy scattering of noggins). Will that be enough do you think? I will probably insulate and line the shed with OSB or play at a later date if that makes any difference?

I also plan to incorporate a breatheable membrane behind the loglap cladding for extra weatherproofing.

Question 3 - I see folk talking about a 1" gap between the cladding and membrane - is that stricly necessary? I was planning to staple it onto the completed framework then fit the cladding over the top, primarily to save the expense of extra 1" battens (this really has to be done on a relative shoestring I'm afraid!).

The Roof
Rather than the troublesome felt roof of the existing shed, I plan to clad it in box-section steel sheets. My original thought was to make some trusses but I've had second thoughts. In order to maximise headroom inside I'm now thinking of a built-up roof with a full-length ridge board and 3" x 2" rafters at 2' spacing. As I can just as easily build the roof in situ, I can't see any reason to use trusses now to be honest.

Question 4 - do you think a 6" x 2" ridge board be hefty enough for a 5m long shed? What about the rafters? Is 3" x 2" enough or should I go for 4" x 2"?


General Stuff
Question 5 - when screwing the framework together are there any recommended screws I should use, or will standard woodscrews be fine? What about using decking screws as I have a quantity of those available already?

Question 6 - I see people mentioning a 'vapour barrier' inside the shed between the wall insulation the inner lining. What material is that barrier? Is it polythene or something a bit more sophisticated! Sorry for the basic, numpty questions - never built a shed before!

Thanks, in advance, for your help!

Mark

 

[the_g_ster]

Base,

Bitumen paint is pretty good, creosote would be good too. From the way I imagine your set up, if it just rests on the flags then if you put a membrane down over the flags, the timber could risk in sitting in puddles created by the membrane rather than draining slowly through the pourous flags. You could but something like damp proof course under each timber, making this less likely.

The crux is it all boils down to longevity you want, this kind of base whatever you do won't last forever, but some bitumen paint won't do any harm. I would steer away from the whole membrane for the risk of not letting moisture into the flags.

Base Insulation

You don't mention anything on insulation for the base, if you want to keep using year round, and to keep your tools from going rusty then I would say you either need to make it bone dry and super warm, or....cold and well ventilated so that rust is formed at a slower rate. The worst option is damp and warm, as everything will rust and fast.

You could try and build in a way of getting insulation in the base walls and ceilings if you want to use year round. It will help even in the summer, as a steel roof will get hot.

Walls

I would put at 600mm centres, but there's not tonnes of lap going on, so 1m should be okay, but shorter would be better if money permits.

If you have OSB sheet on the frame, don't bother with a vapour barrier BUT you must make sure there's a clear void behind the lap to let it breathe and stop the back rotting. You could coat the first 30cms of OSB above the base with bitumen paint to stop any splashed water from run off causing any issues, but you get away without.

Inside you should use kingspan board or something, or poly board. Remember that electrical cable slowly reacts with poly board if in direct contact and reduces the max current carrying capacity (in case you are doing the electrics)

Roof

This will get a fair bit of wind loading and snow too as 5m long, so I would be tempted to have a couple of larger trusses to keep things square when we are being battered by some high winds. As noted, you should insulate it too, you will loose head height, but a steel roof will be the perfect heat conductor, and you will risk condensation on the inside from this, so you will need to think about a vapour barrier and insulation to stop risk of moisture ingress.

 

[Graham Orm]

Hello all,

I've been lurking here for quite some time and very much enjoyed reading about the fabulous projects that are discussed here. I am neither skilled nor experienced enough to be able to contribute much I'm afraid so have never posted before. I've got a project of my own planned now though so have come somewhere I can trust for advice!

We moved into our house a couple of years ago and in the garden is a 14' x 10' shed put up by the previous owners. Nothing special, just a bog-standard, flat-packed shed of the sort that I could get into with a nail-file in about 2 minutes flat! It has a 3" x 2" framework clad with 19mm shiplap - some of which has shrunk so gaps are starting to appear. I have a restoration project I want to house in there so decided to beef it up a bit. However, having given it a good look over I decided it would be easier to start from scratch!

My budget is pretty minimal frankly so I plan to dismantle the existing shed and re-use what timber I can - mainly the 3" x 2" framing. The base is reasonably sturdy so I'll re-use that, extended slightly lengthwise, for the new one.

So here's the plan and a couple of questions I'd be grateful for advice on.

The Base
The existing shed base is good and solid and is made of a number of 3" x 2" timber joists covered with 1" thick sawn timber planks for the floor. This sits on a well-laid, level base of flag stones. I plan to use this base as it is but will add a few more joist to beef it up further and will paint the bottom with bitumen paint to add extra protection. Once built I may cover the floor internally with chipboard for extra strength.

Question 1 - would it be wise to add some sort of waterproof membrane between the joists and the flag stones or will the bitumen paint be enough?
Mark

Yes

The Walls
To save money I plan to re-use the 3" x 2" timber from the existing shed for the new one, then clad it in tanelised 27mm loglap. I've secured the required loglap at a very good price - this is the bulk of the cost of the project so I've had to get what I can for the cheapest price. That means I've had to compromise on the available lengths which are a mix of 3m and 4m rather than the 5m lengths which would allow me to clad the length of the shed in one go. I'll therefore need to arrange a frame member at the appropriate metre multiple to coincide with the cladding joint.

Question 2 - to be as economical as possible with timber, and to work with the round metre lengths of loglap, I'm considering positioning a vertical frame member every 1m (plus a healthy scattering of noggins). Will that be enough do you think? I will probably insulate and line the shed with OSB or play at a later date if that makes any difference?
Mark

That sounds fine, but there is better material out there than OSB for insulating, starting with 75mm polystyrene at about £8 for an 8x4

I also plan to incorporate a breatheable membrane behind the loglap cladding for extra weatherproofing.

Question 3 - I see folk talking about a 1" gap between the cladding and membrane - is that stricly necessary? I was planning to staple it onto the completed framework then fit the cladding over the top, primarily to save the expense of extra 1" battens (this really has to be done on a relative shoestring I'm afraid!).
Mark

The gap is to allow air flow which helps keep damp build up and ultimately rot at bay, your choice really

The Roof
Rather than the troublesome felt roof of the existing shed, I plan to clad it in box-section steel sheets. My original thought was to make some trusses but I've had second thoughts. In order to maximise headroom inside I'm now thinking of a built-up roof with a full-length ridge board and 3" x 2" rafters at 2' spacing. As I can just as easily build the roof in situ, I can't see any reason to use trusses now to be honest.

Question 4 - do you think a 6" x 2" ridge board be hefty enough for a 5m long shed? What about the rafters? Is 3" x 2" enough or should I go for 4" x 2"?
Mark

6x2 but beware of planning limitations on height. There are other 'shed threads' on here that contain the correct spec I think

General Stuff
Question 5 - when screwing the framework together are there any recommended screws I should use, or will standard woodscrews be fine? What about using decking screws as I have a quantity of those available already?
Mark

Decking screws will be fine provided you use enough and they are the right length

Question 6 - I see people mentioning a 'vapour barrier' inside the shed between the wall insulation the inner lining. What material is that barrier? Is it polythene or something a bit more sophisticated! Sorry for the basic, numpty questions - never built a shed before!
Mark

It is what it says on the tin, just ask for vapour barrier at the merchants

Thanks, in advance, for your help!

Mark

Sounds like you've got a good grasp of the job in hand Mark. Good luck with it all, don't be afraid to ask, and post us some pictures, us sad folks on here love a shed picture or two. :wink:

 

[stephenmg]

Thank you both very much. Very helpful.

My revised plan then is,

Base
Paint bottom with bitumen paint and will wrap each bearer in a membrane in such a way that water can't pool. I appreciate this isn't an ideal base so it's a case of doing what I can to delay the inevitable decay as long as possible.
I'll also fit a membrane inside and put down an insulating layer (may use some of the surplus fibre underlay boards I used under my laminate flooring) then cover it in chipboard. Again, not ideal but should provide a bit of insulation without eating into my headroom much.

Walls
Wrap outside with breathable membrane, then fit 25x50 battens to support the loglap and provide an air gap. Inside, fit Kingspan insulation, then OSB lining.

Roof
Box section cladding over 50x50 battens over breathable felt over the rafters. Inside fit Kingspan and line with (thin!) OSB. I think I can just about make it within the 2.5m height limit. The existing shed has been there for about 4 years so the neighbours are used to it (and most of their view is obscured by bushes now anyway) so I'm not too worried if I 'pinch' another couple of inches of height!

Thanks again chaps for your wise words.

One more question - what to use for the windows? How about some of the double-skinned acrylic stuff used on conservatory roofs? Is that a good way to insulate the windows? Its relative opaqueness doesn't bother me because I'd want to 'frost' the windows anyway to deter prying eyes, but how strong is it if used in a window?

Cheers,
Mark

 

[Graham Orm]

Thank you both very much. Very helpful.

My revised plan then is,

Base
Paint bottom with bitumen paint and will wrap each bearer in a membrane in such a way that water can't pool. I appreciate this isn't an ideal base so it's a case of doing what I can to delay the inevitable decay as long as possible.
I'll also fit a membrane inside and put down an insulating layer (may use some of the surplus fibre underlay boards I used under my laminate flooring) then cover it in chipboard. Again, not ideal but should provide a bit of insulation without eating into my headroom much.

Walls
Wrap outside with breathable membrane, then fit 25x50 battens to support the loglap and provide an air gap. Inside, fit Kingspan insulation, then OSB lining.

Why OSB? Ply would be much better for fixing shelves etc to, in fact you won't get a screw to hold in OSB at all

Roof
Box section cladding over 50x50 battens over breathable felt over the rafters. Inside fit Kingspan and line with (thin!) OSB. I think I can just about make it within the 2.5m height limit. The existing shed has been there for about 4 years so the neighbours are used to it (and most of their view is obscured by bushes now anyway) so I'm not too worried if I 'pinch' another couple of inches of height!

Be careful! I ended up with a planning officer here with his tape measure a few weeks after erecting mine. A kindly neighbour...no idea who, had complained

Thanks again chaps for your wise words.

One more question - what to use for the windows? How about some of the double-skinned acrylic stuff used on conservatory roofs? Is that a good way to insulate the windows? Its relative opaqueness doesn't bother me because I'd want to 'frost' the windows anyway to deter prying eyes, but how strong is it if used in a window?
Cheers,
Mark

It's ideal for insulation and for keeping prying eyes out but not thieves, very easy to get through.

 

[stephenmg]

Why OSB? Ply would be much better for fixing shelves etc to, in fact you won't get a screw to hold in OSB at all

I've got no real preference between OSB and ply to be honest - whichever I can get cheapest! Good point about the fixing though.

Be careful! I ended up with a planning officer here with his tape measure a few weeks after erecting mine. A kindly neighbour...no idea who, had complained

Oh :shock: . Well, I reckon I'll be smack on 2.5m as it stands so I should be OK...just!

It's ideal for insulation and for keeping prying eyes out but not thieves, very easy to get through.

OK. Maybe I'll use it as my 'obscuring' layer then instead of frosting film as it'll address that and the insulation issue. I'll fit some grills/mesh inside instead.

Thanks again...M