Shed designs

[Martin Bonner]

We need a bigger shed (OK, OK, it's not news). We've looked at a number of shed places, and none of them look terribly attractive, so we're planning to build our own. SWMBO wants it oak clad with a green roof. It's going to be about 7'x10' (external dimensions), and a green roof can weigh up to 95 kg/m2 - so thats 2/3 ton that the roof has got to support!

I was planning on making the walls of 18mm OSB with 25x50 battens vertical battens at 2' centres. The battens will give something to nail the cladding too while allowing ventilation behind the cladding, and they will also help the OSB resist buckling. The cladding has a profile like |\ | | | | | | \| (excuse ascii art) so will add effectively nothing to the buckling resistance. Cross section OSBOSBOSBOSBOSBOSB batten batten batten claddingcladdingcladdingcladding (battens arranged so that the gap is 25mm, not 50mm - 50mm would be stiffer, but it makes the walls thicker). I was going to put building paper between the battens and the cladding.

Questions:

- Does this sound strong enough?

- where does one buy stainless steel nails for oak cladding (screwfix don't seem to have them)

- Any suggestions for how to detail the corners so that water can't get in the end grain (or at least, can get out again).

- What sort of timbers should I be using for the roof?

- Any useful links (somebody posted some pics of their shed once, but I can't find it again).

- What have I forgotten?

[Frank Erskine]

uk.rec.sheds

[Martin Bonner]

Um, do they discuss the construction of sheds there? My understanding was that the discussions were rather more philosophical (and I don't speak sheddie either).

[Andy Hall]

I bought them from

sourced them for me.

These are the type for pneumatic nailer, but for a shed project, you can easily justify the purchase of a pneumatic nailer.

Mitreing is probably not realistic on this scale.

You could slot each board part way across but not at the ends and slot them together. This exposes the ends deliberately.

You could make corner cappings with the inner corner rebated and the other three corners routed to a profile. These could be attached while being sealed with a suitable sealant in the rebate.

If it's not on view then pressure treated softwood?

My gut feel is that the framing is inadequate. I would have thought at least 75x50mm if not more. Why would there be an issue with thicker walls? Don't you want to insulate it as well?

If you are going to do a green roof, then I would strongly recommend having a look at Norwegian web sites. These are very popular there for summer cabins or even more year round houses in some areas. I stayed in one just over a year ago that had just been built and talked to the owner about it. He told me that even there, this is a specialist job (sort of like thatching is here) and has to be done properly for safety and longevity reasons.

One thing that was done was to incorporate a moisture barrier that seems to be like a very stout pond liner material - somewhat rubbery to the feel - below the turf. There were then various pegs used for retention as well as nets, although the latter has to do with management of snow falling from the roof.

I did notice that the roof angle was quite a bit lower than is typical in UK constructions. This may be implicit in the stuff staying on the roof.

[dennis]

I have just built one..

I used 3x2 battens and ply. I inserted 65mm dritherm slabs to give insulation in the walls, roof and floor. The outside is currently 6mm WBP but I may clad over it when I find something I like.

The walls will support a lot of weight but why would you want to put 2/3 ton on top? Stick with something sensible like shingles and use 18mm ply on 4x2 rafters.

As for the corners.. I have siliconed them and I plan to silicone angle strips over them once it has had a couple more coatings of cuprinol

[Martin Bonner]

"If a job's worth doing, it's worth buying a new tool for". The astute may see a connection between this and my need for a new shed :-)

[snip]

Thanks.

I don't think it needs pressure treating. It's going to be /very/ dry.

Thicker walls = less room inside. I hoped that a double layer of wood (with air gap) would be enough insulation - it's got to be better than my last garage which was single skin concrete block with soil piled up three sides and big gaps where the roof met the walls.

Any suggestions what to search for? It's a long time since my Norwegian was almost as good as my English (I was 2.5 at the time), and about the only Norwegian I have left is Skol, Farn, and "Tuk fur marten" (all phonetic spellings).

[snip]

Yes. Also, you don't actually want the water to run away - the roof wants it.

[Martin Bonner]

Which part of "who must be obeyed" are you having trouble with?

Really? That sounds like it would hold performing elephants! (Assuming the rafters are at 2' centres). Am I just too optimistic about wood strength? (and of course, because it's a roof not a floor, I'm not too worried about flexing).

Hmm. I would worry about silicone trapping moisture. I'm not so concerned about wood getting wet, as it being able to dry out afterwards. (I'm also not planning to treat the cladding - if oak is able to dry out, it is pretty durable).

[TMC]

My gut feeling is that 75 x 50 for the battens would be better but it really depends if you are going for an extensive or intensive roof.

A sedum matting roof would not be as heavy as you suggest and would work with standard frame design

[Paul]

Green roof info:

[Martin Bonner]

info:

Ta.

[Andy Hall]

Up to you, but this is standard for construction timber so why not use it.

if you are not going to "habit" it but only use for storage then fair enough. If you want to spend time in it then insulation will make it a lot more agreeable and reduce cost of heating a great deal.

Not sure. You could start from

enter "green roof" as a search and select "sider fra Norge" to restrit the search. That should give pages including English in Norway.

Also take a look at the Scandinavian Green Roof Institute in Malmoe.

A lot there.

Yes. From what I understand, selection of plant species is important to fit the climate, and it's there that you will need things that will work in the UK, so perhaps then need to circle back to what will thrive here.