Advice re. building a shed

[Mike313]

Hi Folks,
Not strictly a bushcraft question but I know many on here have probably built a shed, so here goes. In the next few weeks I hope to make a start on building a shed and am at the sketching stage. The shed will be timber but built on short 'stub' walls about 18" or so high. It will have a concrete floor slab. I will probably use the floor slab as a place to construct the four wall frames first before I build the walls as I'm tight for space. When the frames are constructed I'll put them to one side while I build the walls. The shed frame would overhand these walls by say 1/2" all round so that the cladding will weatherproof the top of the walls. I am wondering about how I will build these walls. Brick would be nice as it would match the house but I'm wondering if a single leaf of brickwork would be substantial enough. Or would I need a 9" (a 2-brick wide) wall. The other thing that I was pondering is, when I come to fix the bottom 4"x2" member of the shed timber frame to brickwork below (I was going to use the kind of bricks that have 3 hollow vertical hollow 'pockets' and fill them with concrete, I would need to fill them before placing the frame in position) I would either have to drill and rawl-plug or cast in a piece of wood to screw into I guess?
The other option I thought about was using 9" hollow concrete blocks (the type with the 2 hollow vertical pockets). The advantage I see here is that, as the frame will sit on the outside edge of the wall, I could mount anchor bolts in the bottom member of the frame and then concrete them in after I've erected the frame since I can still access the hollow sections of the 9" wide block. I hope that makes sense. The downside is blocks are not as 'pretty' as bricks ...
So I'm not sure which was to go.
Any comments or ideas would be welcome.

 

[Macaroon]

The first and most important thing you need to sort out is where the damproof course is going to be; ideally it needs to be between any brickwork/blockwork/ concrete and the timber structure and all fixings used must not penetrate that damp proof membrane. If your concrete slab and the dwarf walls are high enough out of the ground you could fit the dpm below the top of the walls, but ideally you need to be at least two courses of brick above the prospective highest ground level outside the building.

You don't say how big a shed you're doing or what timbers you're using for the floor frame, but it's surprising sometimes to realise that you perhaps don't need to fix to the base - a shed can be a huge weight and mass, and as long as you can keep everything square during construction, it ain't gonna move.

Give a few more details about the size of thing you propose to build

 

[Mike313]

The shed will be approx. 10 feet square. It will be build on a concrete slab. The dwarf walls will either be 6 brick courses or 2 block courses (both 18"). There will be a ply floor on batten with some insulation between them. A damp proof membrane will run over the slab under the battens and overlap with a damp proof course in the dwarf walls at probably 9" above the slab. The dwarf walls will be battened and insulated like the floor and finished in ply. The wooden frame for the shed will be mostly 4"x2" tantalised timber and finished with ship-lap externalls. The roof will be a mineral felt finish, on plywood on 4"x2" rafters. Height at gutter approx. 6'6" and 8' at ridge.
I'm particularly interested in any comments re building the dwarf walls, brick, block thickness etc.
Thanks.

 

[Macaroon]

The brick/block question is just down to cost and personal preference, no structural reason to use one over the other; I'd go (and have done) with the blockwork as it freed up money for other things. If you don't like the look of the blocks it's very quick and easy to render them with sand and cement at the end of the job and then masonry paint.

I'd do exactly as you propose with blocks, as they're also much faster and easier to lay than face brickwork (unless you're a decent bricklayer already). As your floor will be over a cavity by the sound of it, I wouldn't bother fixing it at all, it'll be heavy and solid enough as it's built and cladded with the ply.

 

[bopdude]

If the shed is attached to and fixed to a concrete base, with walls, will it need planning permission ? I thought sheds had to be free-standing, of course I'm more than likely wrong ?

 

[Mesquite]

If the shed is attached to and fixed to a concrete base, with walls, will it need planning permission ? I thought sheds had to be free-standing, of course I'm more than likely wrong ?

Short answer is no planning permission isn't needed unlees it's a giant size or there's conservation planning restrictions in your area.

Brick built or wooden sheds can be built so long as they're under a certain size and height. For the exact maximum size you can build you'll need check with your local planning office

 

[bopdude]

Short answer is no planning permission isn't needed unlees it's a giant size or there's conservation planning restrictions in your area.

Brick built or wooden sheds can be built so long as they're under a certain size and height. For the exact maximum size you can build you'll need check with your local planning office

Thanks for that

 

[Mike313]

Thanks for the feedback folks, if you have any other thoughts keep 'em coming!

 

[Mesquite]

Have a look at the video Colin Furze did when he built his shed. Seriously sturdy shed, well insulated and will last you a long time.

[video=youtube;LP67MAoihZk]https://www.youtube.com/watch?v=LP67MAoihZk[/video]

 

[Macaroon]

I've had this in my mind whilst outside strimming, because I'm about to build a workshop myself; one thing that stuck in my mind is that you're going to be spending a good bit on timber for a floor to span 10'X10'.

I went to price up the timber for my 16X8 about eighteen months ago and nearly had a heart attack! :yikes: But my brother who is a working chippy tells me timber prices have rocketed since then.....Oh dear!!!

 

[Mike313]

Thanks folks. Good video that
As regards the price of wood, I'm putting a list of what I need together, then I'll send it out to a couple of suppliers to get quotes, I expect I will probably be a bit shocked when I get prices!

 

[dewi]

Shame you're not up north... I'm about to get shut of a 12ft x 8ft dutch barn style shed. Having a 25ft x 25ft log cabin built to replace it as I need more space.

 

[Janne]

Hi Folks,
Not strictly a bushcraft question but I know many on here have probably built a shed, so here goes. In the next few weeks I hope to make a start on building a shed and am at the sketching stage. The shed will be timber but built on short 'stub' walls about 18" or so high. It will have a concrete floor slab. I will probably use the floor slab as a place to construct the four wall frames first before I build the walls as I'm tight for space. When the frames are constructed I'll put them to one side while I build the walls. The shed frame would overhand these walls by say 1/2" all round so that the cladding will weatherproof the top of the walls. I am wondering about how I will build these walls. Brick would be nice as it would match the house but I'm wondering if a single leaf of brickwork would be substantial enough. Or would I need a 9" (a 2-brick wide) wall. The other thing that I was pondering is, when I come to fix the bottom 4"x2" member of the shed timber frame to brickwork below (I was going to use the kind of bricks that have 3 hollow vertical hollow 'pockets' and fill them with concrete, I would need to fill them before placing the frame in position) I would either have to drill and rawl-plug or cast in a piece of wood to screw into I guess?
The other option I thought about was using 9" hollow concrete blocks (the type with the 2 hollow vertical pockets). The advantage I see here is that, as the frame will sit on the outside edge of the wall, I could mount anchor bolts in the bottom member of the frame and then concrete them in after I've erected the frame since I can still access the hollow sections of the 9" wide block. I hope that makes sense. The downside is blocks are not as 'pretty' as bricks ...
So I'm not sure which was to go.
Any comments or ideas would be welcome.

A few questions: as you do the built "from scratch" why do you want to do a slab then insulate it? You might as well do an insulated and damp proofed slab from scratch.

You mention you want to construct the frames for the walls first. Why not construct the walls on top of the concrete/block construction?
There is a risk your premade frames will not fit well, you have then wasted time and money.

Rendered blockwork is much easier than bricks.
Remember you need to fix a horisontal batten securely on top of the top blocklayer. Pressure treated timber, with galvanized bolts with spaced multiple nuts that are spaced so they go in the middle of the block cavities, poured concrete.

If you want it strong, do not forget rebars that connect the slab and block walls.
PM me.

 

[paulds]

Damn Dewl, if I wasn't skint I'd have that off you!

 

[Mike313]

Sorry for the delay in replying, folks, and thanks for your comments.
Dewi, that's a lovely shed, yes it's too far away from me unfortunately.
Janne, The base is part of a bigger concreting job that we are getting a builder to pour for us as it's just too big a job for me at my age and with a bad back etc. I will be helping but he will do all the heavy work. The concrete will be on two levels with steps between levels. The shed will sit on the larger, lower part of the slab. We have practically no flat or level ground in the garden to lay down the framework when it is being built - we have had to shift tons of earth to make a level platform for the new slab. I will be building everything by myself with generally no help so it is easier for me to construct the frames on the flat and stand them on the dwarf walls later (I'll have some help with this) rather than to try build the frame in place on the dwarf walls on my own. So the idea is that once the slab is built, it will be the perfect area to build the framework for the 4 walls, brace them well, then store them elsewhere in the garden and then build the dwarf walls. I will set out the walls to suit the dimensions of the frame. These dimensions should be easy for me to maintain correctly as I will be constructing just 2 block courses. The first course of blocks will be anchored to the slab with eight 6mm bars which I will drill into the slab, 2 per side, using a chemical anchor compound and the blocks filled with concrete. The second course will sit on a damp proof course which will overhand on the inside. When the frames are positioned, the base of each frame will have bolts already in them and these will sit into the cavities of the blocks. When the frame is in place, these cavities will be filled with concrete and, when it has set, the bolts will be tightened. I'm expecting it will take me a few weeks to complete the shed and I was concerned that a cast-in damp proof membrane might get damaged at the point where it comes out of the slab during that time. What I hope to do is, I will floor the shed with plywood on a grid of say 2"x1" laths and under these laths there will be a damp proof membrane which will be carried up the dwarf walls and glued to the overhanging damp proof course in the dwarf walls, The dwarf walls will then be insulated and ply lined also. I have a detail for the ply so that no fixing is made through the damp proof course or membrane. All the wood I will be using is tantalised and the ply will be exterior grade and I will be sealing the edges of the sheets for added protection. What you think?
I haven't started yet as I am waiting for the builder do the slab.

 

[Dogoak]

On the jobs I've done DPM goes under the concrete slab (on top of flattened/compressed hardcore) so you don't get damp rising up through the slab. Concrete slab should be above ground level with DPM between slab and first course of block work. Your builder should be able to advise.

Good idea constructing the frames on the slab, I'd do the same.

Personally I think the bars into the slab are a bit overkill, the blocks will be cemented onto the slab, normal procedure. Again, if it was me, I'd give the bolts a miss, use solid blocks and use some short lateral restraints fixed to the inner of the blocks and then onto the top of the bottom of the frame, DPM again between top of block and frame. Again, have a word with your builder for guidance.

Sound like a great project, hope your going to give us photographic updates?

 

[Janne]

As the shed is on a level below the other slab part, you might get water running down towards the shed. maybe a channel to remove this water could be incorporated just outside the planned wall?
Yes, damp proofing under the concrete is a must. Additional DPM in the walls.
I am not a builder, so I rather overengineer things.
I have a bad back too, and prefer to work standing up, hence my recommendation to do the wood work on top of the concrete walls.
I would also do the block work with the door frame in place.

Will the shed be heated? Insulation in the walls needed?

My last project similar to yours was a few years back, I made a 6 sided Cabana. Had the base made from reinforced concrete. The builders made it symmetrical lozenge shaped. Because of this it was hell to do the roof. Every single beam and ceiling plank was different.

 

[Mike313]

Hi Dogoak, yes I know the bolts into the slab are overkill but similar to what Janne says, I have an inclination to over-engineer things. I also kind of enjoy knowing it's a 'belt-and braces' job. I still remember the story of the 'Three Little Pigs' and don't want any winter storm to 'huff and to puff and to blow my shed down' Ha ha!
Hi Janne, yes, I intend to make up the door frame, brace it well and build the blockwork tight to it. The shed will have a single bar electric heater for cold days. I don't plan to insulate the walls to start with - just wrap up well and plug in the heater when it's cold. But it is something I can consider in the future.
Thanks guys for your advice.