Build a shed Mike's way, without concrete

[MikeG.]

There have been a number of enquiries lately from people who want to build a shed, but are worried about building a concrete base and laying a brick plinth. Whilst that remains the best way by far, I thought I would put together a thread for people who wanted a concrete-free alternative, without bricks. Please note that you should not attempt this technique for large buildings (say 20sq m or more), nor for buildings which need to show compliance with Building Regulations. If you plan on using a large lathe regularly I would also avoid a timber suspended floor, and would refer you tomy original thread on workshop building.

The principle of this alternative construction is to use readily available and cheap concrete lintels (from any Builders Merchant) to raise the timber the necessary 150mm above the ground. There is a minimum of digging, but topsoil must be removed around the perimeter, as well as all vegetation.

I show 2 alternatives, with the difference being the span of the floor.

Here are the drawings:

Here is my typical corner detail for feather-edge boarding (this is a Plan Section):

Everything above the floor remains as per my original thread, and of course there are a myriad alternatives for the roof.

Now, I really should get on with some work!

 

[MikeG.]

I would just add that we get a number of people asking about buying a pre-made shed and erecting that on paving slabs and the like. Again, getting it up off the ground will prolong its life enormously, and I would urge those considering this way of procuring a shed to lay the concrete lintels as I describe above, and place their new shed on the top of that.

 

[PAC1]

I built my workshop/shed off three honeycombed dwarf walls. I dug and installed strip footing (the width of the shed) just in from each end of the shed and one central. then built three courses of honeycomb wall and fixed a wall plate on DPC above. I then ran the floor joists the length of the shed. I then laid 3/4 plywood floor and then built the shed off of the floor. 20 years later it is still good. The only downside is that the floor is about 15-18" above ground level so needs a ramp for machinery installation.

 

[MikeG.]

This alternative is aimed strictly at those who don't want to lay any concrete or bricks. There are a thousand and one ways of building a decent shed, but the options narrow considerably when you take bricks and a footing out of the equation. Too many people just plonk the timber on a paved area, then wonder why it rots in a handful of years. I have spent too long describing to people how to avoid this, so thought it time to actually do a drawing and show them how it's done.

 

[PAC1]

This alternative is aimed strictly at those who don't want to lay any concrete or bricks. There are a thousand and one ways of building a decent shed, but the options narrow considerably when you take bricks and a footing out of the equation. Too many people just plonk the timber on a paved area, then wonder why it rots in a handful of years. I have spent too long describing to people how to avoid this, so thought it time to actually do a drawing and show them how it's done.

Mike I understood the aim. But your design requires a longer length of footings to be dug and more concrete. It is just that the concrete is precast rather than site cast. You also say crushed concrete in the footings. My method minimises the overall length of footings, concrete and brick by having 3 widths rather than 2 lengths and 2 widths. If you wanted to save bricks you could just have two courses of honeycomb wall.
Take a shed 16' by 8' your method has 48' of footing and precast concrete mine would only have 24' of cast concrete and then 96 bricks. Then there is rebar in your pre cast concrete. I doubt there is much between the two approaches in CO2 emissions.

 

[ScaredyCat]

Interesting, I wonder what your take is on what I made for a potting shed, it's held up so far but I'd be interested in opinions.

The cross pieces are pressure treated, under the fine gravel is broken brick chunks from the wall I found that the builders had left , when I dug out (it goes down about 10 inches. Shed sits on runners purpendicular to the cross pieces.

 

[transatlantic]

I did mine with the plastic shed base kits. The existing floor is a massive concrete slab. On that, I have the plastic grids filled with gravel. Then the bearers. Then the actual flooring.

So basically this, but it was a concrete slab, not grass.

 

[MikeG.]

........Mike I understood the aim. But your design requires a longer length of footings to be dug and more concrete. It is just that the concrete is precast rather than site cast. You also say crushed concrete in the footings. My method minimises the overall length of footings, concrete and brick by having 3 widths rather than 2 lengths and 2 widths. If you wanted to save bricks you could just have two courses of honeycomb wall.
Take a shed 16' by 8' your method has 48' of footing and precast concrete mine would only have 24' of cast concrete and then 96 bricks. Then there is rebar in your pre cast concrete. I doubt there is much between the two approaches in CO2 emissions.

I'm not suggesting doing it this way to reduce CO2 emissions. I am suggesting this technique so that people who don't have the skills to lay bricks, or the money to cast concrete, can have a better shed than just setting the thing on the ground. This isn't a contest. There are lots of ways of achieving the same thing. For good or ill, hundreds of people over the years have built sheds to my directions, and I have no doubt they'll continue to so do.........so the purpose of this thread is to provide them with an alternative to my preferred slab-and-plinth design. I have worked hard to keep the floor level low, to avoid the big steps you have, and also because of the height restrictions of Permitted Development outbuildings. As soon as you say "honeycombed dwarf wall on strip footings" (how do you keep vermin out of there?) you are missing the point of the thread.

 

[MikeG.]

Interesting, I wonder what your take is on what I made for a potting shed, it's held up so far but I'd be interested in opinions.

The cross pieces are pressure treated, under the fine gravel is broken brick chunks from the wall I found that the builders had left , when I dug out (it goes down about 10 inches. Shed sits on runners purpendicular to the cross pieces. .....]

The principle I am trying to get across is to raise the lowest piece of the timber wall 150 above ground level. Your approach is better by a mile than sitting the shed on a patio or paving slabs, as so many do, but it doesn't achieve the raised sole plate which I consider a fundamental of a long lasting building.

 

[MikeG.]

I did mine with the plastic shed base kits. The existing floor is a massive concrete slab. On that, I have the plastic grids filled with gravel. Then the bearers. Then the actual flooring.

So basically this, but it was a concrete slab, not grass..........

Again, loads better than the typical, but it still leaves the bottom edge of the structure vulnerable to damp, and therefore rot. Depending on ground conditions and levels, it is possible that such a mat could fill with water if it is sitting on an impermeable base such as concrete.

 

[transatlantic]

I did mine with the plastic shed base kits. The existing floor is a massive concrete slab. On that, I have the plastic grids filled with gravel. Then the bearers. Then the actual flooring.

So basically this, but it was a concrete slab, not grass..........

Again, loads better than the typical, but it still leaves the bottom edge of the structure vulnerable to damp, and therefore rot. Depending on ground conditions and levels, it is possible that such a mat could fill with water if it is sitting on an impermeable base such as concrete.

Yeah fair enough. I had considered that the concrete slab isn't going to be flat, and water could pool on top of it under the bearers, but I think it will be very unlikely to pool enough (45mm) to reach the bearers. I think if my garden ever flooded that bad I have bigger problems

 

[MikeG.]

The pooling water thing was only an aside. Falling water will bounce quite a long way even off shingle (pebbles), so to remain adequately dry timber should be well up above whatever the surface is, and able to drip dry. I'll bet if you look at your shed after rain you'll find the bottom couple of boards are damp even after the ones above have dried off.

 

[transatlantic]

The pooling water thing was only an aside. Falling water will bounce quite a long way even off shingle (pebbles), so to remain adequately dry timber should be well up above whatever the surface is, and able to drip dry. I'll bet if you look at your shed after rain you'll find the bottom couple of boards are damp even after the ones above have dried off.

Yeah - probably :-(

 

[John Brown]

Maybe you coud get the mods to add this to your original thread, as the instructions stand the risk of being lost in the noise here.

 

[MikeG.]

I've asked them to make this a sticky, so it should sit at the top of the sub-forum alongside my other one.

 

[Duncan A]

Thanks for taking the trouble to draw and post this, Mike.
I may have to replace a shed soon (yep, the bearers were placed directly onto paving slabs) and this will certainly be one way of keeping the job simple, it's a great idea.
Duncan

 

[MikeG.]

Thanks for taking the trouble to draw and post this, Mike.
I may have to replace a shed soon (yep, the bearers were placed directly onto paving slabs) and this will certainly be one way of keeping the job simple, it's a great idea.
Duncan

No problem, Duncan. Feel free to ask about it at the time.

Those drawings took an hour or two, but will actually save me hours of typing in the long run, and I was clutching around at the time for anything that would stop me getting on with some work.

 

[dom68]

hi mike is it necessary to use prestressed lintels or is just reinforced ample? as in fence posts..

would it be possible for me to cast my own lintels in some kind of form using reinforcing rods?

thanks..

 

[dom68]

also is it advisable to use treated timber for the frame?

ta.

 

[MikeG.]

Frankly I doubt it makes much difference. Timber framed buildings are treated as a uniformly distributed load, so as long as the lintel is correctly bearing on the substrate along its length it will only be in local compression. My hunch (unproven) is that you won't be able to cast your own as cheaply as you can buy them. I don't think you'll find a fence post which is 150 in one dimension. The ones I am familiar with are about 100mm square, and although that is better than sitting the shed on the ground, it isn't really high enough.

Treated timber? Absolutely. Don't even think of not doing so.