Small Shed

[Ed Turtle]

Hi, hope this is allowed, after its not a workshop?! The new shed will allow me to clear the garage out though, so i can have a workshop in there instead.

I'm planning a 6 foot by 6 foot shed, but need a little assistance with some of the details.

Firstly, I'm undecided on the base. I have in mind either a concrete base, or paving slabs. I can get some paving slabs for free (3x2 slabs), but the bricks i have are old imperial ones, so will need cutting when i lay them around the slabs - I wont lay them straight on the slabs, which is the next potential problem. The bricks are probably not acceptable to go underground, and i cant mix and match with engineering bricks due to the size difference. Would it be OK to do the foundations for the bricks around the outside of the slabs, so that the foundations are 2 inches underground (or more if needed), and 2 inches over ground, with the top of the foundation being level with the top of the slabs? Have i explained that right ?! :? :?
If i do pour a slab would this a)be more advantageous in any way? b) Would three inches be thick enough, going to four inches at the outside?

Next up, i recently built a summerhouse/playroom and i really like the design, so will copy for the shed, hopefully avoiding the mistakes i made...

First up, i used 2x2 with diagonal bracing at between 450 and 600 centres, i was going to go with 400 spacings on the short side, but lock down meant i ran out of wood so i used 600 instead. It is plenty sturdy for a shed, and the diagonal bracing helps enormously. I have been offered free osb, so the plan this time is to use that inside instead of the diagonal bracing, but order enough wood this time to do 450 spacings.

I used a three inch post at the corners, which left an inch for the feather edge, so worked out well. This time i have been offered free 4x2 wood, which would be nice to use, but i cant see how it would with the three inch corner posts, unless i could put a 2x2 on the post inside to make up the difference? I guess i could buy a table saw and rip it all to 2x2 if it wont work. One thing i really cant visualise is if i use the 4x2 with three inch corner posts, what would i do around the door opening? I was going to have a 2x2 frame, with a 4x2 door frame, so i had an inch outside for the feather edge to butt against, and an inch inside to butt the osb against, but if I'm using 4x2 frame, how would this work?
With the summerhouse i made, i used 2x2 frame and then i used 3x2 for the rafters (fibre cement roof slates), at 600 centres to line up with the 600 centres on the wall. This seems strong enough (i did also use some 2x1 for ties, probably not strong enough but its only small), but the shed will be slightly larger, so i was going to use 4x2 for the rafters, would this work with a 2x2 frame? I will be using real slates this time, or fibre cement slates, haven't decided on a pitch yet, but it will be fairly low.
Does it matter that the 2x2 is not inline, it was only to give me something to nail the feather edge boards to, i didnt think it was structural, but now i look at it, i think i should have probably made more of an effort to line them up

Finally (for now!), i used angle brackets screwed into the bricks to anchor it down, which works fine, and means i have a slight gap under the wood to allow air through (except under the corner posts). The only problem i made is not putting a damp course underneath (I put it in the top mortar course instead), so rain does drip onto the mortar course, and does blow in. Not a major problem because the front is open, so v draughty, and there is a gap under the wood. Not good for the brackets though. Is there anything i can do here? With the shed, if i put a 4x2 on the mortar layer, with the dpc stapled to it, then tucked back up, will it cause problems for me? I wasn't going to counter batten as there's no need with feather edge, but will it allow enough air flow if i don't? especially if i put osb on the inside too?

and outside, not a huge amount of overhang, but enough to catch a little rain

Thanks for looking, and also providing all the projects you've done on here, I've read nearly all of them, all really informative too. Hope this project will interest some of you, even if its a bit small?!

 

[MikeG.]

If you use OSB you'll want to do stud spacing which suits that, so 600 (ish) or 400 (ish).....not 450. The "ish" relates to whether or not it is metric or imperial.

For a base, can I suggest you look at both of the threads in my signature. If the concrete-free one suits your building, and I can't see why it wouldn't, then you could lay slabs on the ground inside that if you waned, leaving out the suspended timber floor. Raise the slabs up a few inches on sand and you won't be tripping over a raised threshold every time you go in or out.

 

[Ed Turtle]

I'm glad you noticed and replied to this thread, thanks. You definitely are the shed/workshop oracle.

I think the osb is 8x4, but i'm thinking of getting a table saw anyway, so i can always cut it to suit if needs be. I'll wait for the sheets before doing the framing anyway, as you say to make sure.

I'll have another look at your floor suggestions, i'll probably have more questions

 

[Ed Turtle]

For a base, can I suggest you look at both of the threads in my signature. If the concrete-free one suits your building, and I can't see why it wouldn't, then you could lay slabs on the ground inside that if you waned, leaving out the suspended timber floor. Raise the slabs up a few inches on sand and you won't be tripping over a raised threshold every time you go in or out.

The one in your signature shows you building it on a concrete lintel, but I already have the bricks here, so would prefer to use them. Would that be possible?

Is the air gap absolutely essential on a shed (rather than an insulated workshop)?

 

[MikeG.]

Bricks can't really be used dry, and therefore need a foundation. So by all means dig a trench and fill it with concrete, then build up with bricks. Then you have the options of following the suspended floor diagram in the "no concrete" design, casting a ground-bearing slab in concrete, or spreading sand and laying paving slabs. I'm not 100% sure which gap you are asking about, but if you do a suspended floor then you need an air gap under it, and any building should have a gap behind the cladding to allow the back of the boards to dry off.

 

[Ed Turtle]

Thats what i was querying, whether i can dig a trench for the foundations, but have the foundations coming up above the ground by two inches, as well as underground by a few inches too.

I was referring to the gap behind the cladding in this case. Since i wont be insulating this shed, would it be ok to have a 2x2 framework for the walls, on the inside the osb, and on the outside the f/e boards, so with no insulation there would be a 2inch gap, except where the f/e boards are nailed to the frame?

 

[MikeG.]

You can do that with the concrete if you want, but I'm not sure why you would.

If it is an unheated, uninsulated store shed only, then put the OSB on the outside of the frame to protect the frame, and then batten out outside that. There needs to be a gap behind the cladding if you want the cladding to last, and if you want to keep the frame dry.

 

[Ed Turtle]

You can do that with the concrete if you want, but I'm not sure why you would.

Just to keep the bricks out of the ground, protect them from frost. Not necessary?

If it is an unheated, uninsulated store shed only, then put the OSB on the outside of the frame to protect the frame, and then batten out outside that. There needs to be a gap behind the cladding if you want the cladding to last, and if you want to keep the frame dry.

Yeah, not going to be used as anything other than a shed. Is the method i've used in the pictures above an ok approach? ie no OSB. And i had considered lining the above summerhouse with ply or osb, would that give me a problem if i did?

 

[MikeG.]

You can do that with the concrete if you want, but I'm not sure why you would.

Just to keep the bricks out of the ground, protect them from frost. Not necessary?

Many/ most bricks are suitable for laying in the ground. Look at every brick house in Britain.....you don't see concrete showing at the bottom.

 

[Ed Turtle]

Thats true, but i had thought they used engineering bricks for the bottom few courses, but now i think about it what you say makes sense, i just wasnt really thinking about it properly :roll: :?

Kind of a moot point possibly though, as now i've got the old shed up, the slab underneath looks really good (only one v small soft spot in the concrete in the middle, about 8mm deep. I had hoped to actually use the old slab for the new shed, but a few q's arise:

1) Can i extend the old slab from a 6x4 to a 6x6, ie add a 2foot by 6 foot extension on to the side? I can create a 'day joint' here, but perhaps prime the old slab edge with sbr slurry first?
2) Can i put a thin self levelling screed over the two slabs in a few months time, or will it always crack at the interface?
3) The old slab looks a min of four inches all round, except under one edge where it looks about two inches, i can my spade under it (not sure how far at this stage). Could i dig under a bit, then add another four inches of concrete to underpin it?
4) Whats best in this instance, either build the brick plinth straight off the slab, or dig foundations around the slab and build up the bricks around the outside?

Thanks, will get some pics of progress tomorrow.

 

[MikeG.]

........1) Can i extend the old slab from a 6x4 to a 6x6, ie add a 2foot by 6 foot extension on to the side? I can create a 'day joint' here, but perhaps prime the old slab edge with sbr slurry first?

You can, but it's not ideal. I suggest drilling into the edge and setting some starter bars in there with an epoxy, to lock old and new together.

2) Can i put a thin self levelling screed over the two slabs in a few months time, or will it always crack at the interface?

You can, and it will.

3) The old slab looks a min of four inches all round, except under one edge where it looks about two inches, i can my spade under it (not sure how far at this stage). Could i dig under a bit, then add another four inches of concrete to underpin it?

You can.

4) Whats best in this instance, either build the brick plinth straight off the slab, or dig foundations around the slab and build up the bricks around the outside?

Best? Dig up the slab and lay a proper one. If it was a workshop, I'd push that strongly. For a store shed you may as well build on top.

 

[Ed Turtle]

Yes, i had considered that, but as you say since its a small shed not a workshop, i dont think its worth the hassle.

Thanks

 

[Lons]

Not what you want to hear and likely Mike won't agree but reading what you say that it's just a shed to store some stuff personally I wouldn't bother as it seems ott.

I would ( and have done several times over the years ), just lay a slab base with the slabs you have, make a base out of treated timber with no gaps to exclude vermin and build your shed on top, it's quick, cheap and will last for many years if you treat it then you can spend the time and money saved on your workshop.
I currently have one that's been up and weatherproof for more than 15 years with the odd coat of stain and new roofing felt just this year.

Another factor maybe, are you likely to still be in that house in 10 - 15 years or will have moved? If you build it in sections you can take it with you. I've done that as well but then I'm allegedly a cheapskate.

 

[Ed Turtle]

Thats ok, i like hearing other options! I am definitely a cheapskate, i'll recycle old slabs, bricks, sand etc... i normally manage to get most stuff for free, then end up just paying for the cement.

I didnt get any slabs this time though, so i'll just put it on the shed base thats already there, extending it slightly.

Can i put a thin self levelling screed over the two slabs in a few months time, or will it always crack at the interface?

Is there anything i can put down to stop the crack? I thought of laying some porcelain tiles in the shed, could that work??

The old slab looks a min of four inches all round, except under one edge where it looks about two inches, i can my spade under it (not sure how far at this stage). Could i dig under a bit, then add another four inches of concrete to underpin it?

Two q's from this,
1) how far under the old slab should i go, and how deep?
2) Could i also extend the slab here out by just four inches, going under the old slab at the same to reinforce, and also then having a four inch 'extension' to lay the bricks on, i appreciate that the join may crack again, but should be hidden/less visible if its where brick wall starts. In this way at least i'd know for sure that the wall/brick plinth is at least on something more sturdy than 2inches of concrete.

Thanks

 

[Ed Turtle]

Ok, slabs now sorted as per mikes suggestion earlier. So I have a 6x6 slab (1.8m x 1.8m). Ready to put the bricks on, definitely going with at least two courses, but possibly three.

I have enough 4x2 here to do a sole plate, wall studs at 600 centres and a double top plate. I was going to do the roof with 3x2 at 600 centres, so is there any need for a double top plate, if i align the rafters with the studs?

What should i use for a ridge board, is 4x2 overkill? With the previous shed i built i had a (i think is the correct term) ridge pole, directly over the centre stud, which holds up the ridge. In this instance at the back i can do the same, but at the front i want to have a door in the centre (probably two doors at 2feet each). How do i hold up the ridge here, will a 4x2 over the centre of the top plate be ok? Is this a case to have a double top plate? Would a 4x2 be considered a structural ridge? I intend to use rafter ties (Joists?). Would 2x1 on either side of each rafter be ok? Just up from the top plate, not directly on it.

Finally, not going to have osb now, so from the outside it will be f/e, then 4x2 framing. Is that ok? Will i need to batten the f/e out? I may do this anyway, so i get a bit of an overhang to aid rain runoff. Without the osb, whats the best way to brace it? Would a 4x2 inside two studs diagonally be ok? One down to the floor on one end, then going up from the floor the other (to form a v shape, but with a gap at the bottom, like this: |\| |/| )

Thanks

 

[MikeG.]

.......I have enough 4x2 here to do a sole plate, wall studs at 600 centres and a double top plate. I was going to do the roof with 3x2 at 600 centres, so is there any need for a double top plate, if i align the rafters with the studs?

No need for a doubled plate if the rafters align with the studs.

What should i use for a ridge board, is 4x2 overkill? With the previous shed i built i had a (i think is the correct term) ridge pole, directly over the centre stud, which holds up the ridge. In this instance at the back i can do the same, but at the front i want to have a door in the centre (probably two doors at 2feet each). How do i hold up the ridge here

No, 4x2 is bare minimum. I know it's only a small roof, but the ridge beam is all that stops the walls spreading. You need a proper lintel over the doorway (doubled 4x2 supported on cripple studs, hard up underneath the plate)to take the load from the short post supporting the ridge.

....... I intend to use rafter ties (Joists?).

No need, as the ridge is structural. Never use tiny ties as you suggested, because people always store stuff up there.

Finally, not going to have osb now, so from the outside it will be f/e, then 4x2 framing. Is that ok? Will i need to batten the f/e out? I may do this anyway, so i get a bit of an overhang to aid rain runoff. Without the osb, whats the best way to brace it? Would a 4x2 inside two studs diagonally be ok? One down to the floor on one end, then going up from the floor the other (to form a v shape, but with a gap at the bottom, like this: |\| |/| )

No, you'll need a breather membrane outside your studs, with battens outside that. To prevent racking you've got two choices: bracing built within the wall thickness as you suggested, but not to that design, or, more simply, 4x1 planted on the inside face of the studs and plates going from the bottom centre up to the top outer corners of each wall. Having a big hole cut through one wall for a door complicates matters. If you do decide to do 4x2 braces withing the thickness of the wall, then it will have to follow the same pattern as I just described for the 4x1, and this will mean only the outer edges of each wall panel, and one stud in the middle, will be full length. All the others will need cutting in around the diagonals. It's a much longer job, but produces a neater wall internally.

 

[Ed Turtle]

No need for a doubled plate if the rafters align with the studs.

Thought as much, Ta.

No, 4x2 is bare minimum. I know it's only a small roof, but the ridge beam is all that stops the walls spreading. You need a proper lintel over the doorway (doubled 4x2 supported on cripple studs, hard up underneath the plate)to take the load from the short post supporting the ridge.

To clarify three things. 4x2 will be ok? This only applies to the front? Whats a cripple stud?

No need, as the ridge is structural. Never use tiny ties as you suggested, because people always store stuff up there

At what point does the ridge become structural, i assume looking at a span table its the minimum thickness for a particular span? ie 4x1 is a ridge board, not beam? Also, not going to be storing anything up there. (in theory)

No, you'll need a breather membrane outside your studs, with battens outside that.

Is this the case even if i dont use any insulation? I already have non-breathable roofing membrane (from another job), I assume this is no good? I will use it on the roof though.

 

[Ed Turtle]

Any more thoughts on the breather membrane as mentioned above? Do i need it if i dont insulate? Can i use non-breathable roofing membrane, or will i be better off using nothing?

Thanks

 

[DBT85]

If I recall the membrane is there to allow moisture out but not in. Its cheap and does a good job. I can't imagine why you'd try and get away without it.

 

[Ed Turtle]

Its really just something i cant see that i'd need, and i dont want unnuessecary expense. Having said that, i CAN see why its needed for a workshop, but not for a shed. Just want to know if i'm missing something, and i do NEED it.

Another q, the ridge pole at the rear of the shed will not be directly over a wall stud, does this mean i need a double top plate in this instance?

Thanks