Foundations for a big - ish shed.

[jamieled]

For the next phase of construction here we need a big-ish shed. This is mainly for forestry - mechanical work on the machines and storage of kit. We've been working out of a shipping container for a while but that's not ideal on a number of fronts - no power/lighting and there's a bit of condensation in winter which doesn't help tools etc.

 

It'll probably be a stick built timber shed, as that's easy enough to DIY, and timber cladding will be in keeping with the house. There's no need for full planning or building regs due to the end use.

Somewhere in the region of 12-15m long by 5-6m wide, rectangular box. Likely using bought in trusses for the roof to keep it simple. Ground has been cleared and flattened by previous owners. We think it's primarily compacted rock, but trial pits have never given much insight as the digger we had was was too small (and ground too hard for it to achieve much). Q's:

 

1) I think we'll need a concrete slab for the garage/workshop area, probably with some reinforcement if it's going to take a tractor or such like. Is it essential to dig/pour footings as well, or can the shed sole plate just be fixed to the edge of a slab which is the same depth all over? I'm prepared to accept some risk here and not necessarily build to the standard of domestic housing, equally if it's all going to fall down quickly that's not much use either.

 

2)What thickness of slab and spec?

 

3) In the future we may need to hive off a small corner of it for an office. If we need to do this, then my plan was to build a timber floor above the concrete slab that can be insulated (essentially it will have a couple of steps up off the slab into the office). This is the easiest way I could think of building a small insulated room within a largely uninsulated building. Any particular problems with that approach, or any better ideas?

 

As none of this requires structural design for building regs submission, there's currently no structural engineer involved. At some stage I guess a building gets big enough, or the consequences severe enough that it's essential, so we may need to go down that route if the answers are not obvious. 

 

Cheers in advance.

[saveasteading]

3 hours ago, jamieled said:

none of this requires structural design for building regs submission,

 

have to check if there is exemption for forestry.

 

3 hours ago, jamieled said:

ground too hard for it to achieve much)

so it is strong enough.

3 hours ago, jamieled said:

probably with some reinforcement if it's going to take a tractor

No, it doesn't need reinforcement for the tractor, as it isn't about to fall through. reinforcement is for crack control.

 

3 hours ago, jamieled said:

Is it essential to dig/pour footings

you should have a deeper perimeter about 400mm below ground, for strength and to be below frost and other weather effects.  

3 hours ago, jamieled said:

thickness of slab and spec?

100mm would do it if yo can be that precise, on top of 150mm of good compacted stone, on compacted ground.

Reinforcing mesh A142 at mid depth, using spacing blocks.

 

3 hours ago, jamieled said:

may need to hive off a small corner of it for an office

now you are possibly into regulations. it then needs to be much stronger for  regular occupation.

If you were challenged on it you might have to show that the space was seldom used, and not for long.

 

3 hours ago, jamieled said:

Any particular problems with that approach,

No that is sensible, as long as the occupier is safe. Structure, fire escape etc. Imagine the tractor going on fire: would the office occupier know, and be able to escape?

 

 

 

 

[Russell griffiths]

At that size I would look at a steel portal frame. 

Not the RSJ type but the galvanised uprights and rafters, you get feet that bolt down to your slab and then the uprights bolt to that, far more ridged than timber, better rot resistance. 

Just put timber cladding over it. 

Floor slab I would go 250- 300 mm perimeter with 150mm slab over the rest of it, put mesh in it and it will be there after your long gone. 

[gc100]

On 28/02/2023 at 21:15, jamieled said:

There's no need for full planning or building regs due to the end use.

I think you are miss informed on that. If you are building in woods planning will always be refused unless it’s for forestry - however you still need permission and will need to prove activities etc.

 

Normally anything over 30m2 needs building regs as well (fire, structural etc)

 

 

 

 

[Canski]

30 m2 in the woods would suit me now. 😀😀

[Nickfromwales]

Simple option is to go for an insulated raft, with 300mm of EPS 100 under it and a 120mm reinforced slab with tied A142 mesh. If the ground is that hard, a raft is a no brainer.

It'll make for a much nicer working space ( slab won't be ice-cold ) and you could ( I never said this, right  ) install UFH i it, zoned for the working space, and for the "office" area accordingly.

You will, never again, mention the word "office", or document anywhere this repurpose of that internal space, it if it coms to fruition, so we bear no guilt in telling you to strap a manifold and ASHP to the slab and heat the "office" and "workshop" as you then please. I know I would, without a second glance. Or, just be happy that the "office" has an insulated floor, and retro-fit A2A AC ( for heat & cool ).

 

If you want to work on tractors in the depths of winter, you'll thank me for the above. 

[SuperJohnG]

I've got 10m x 6m shed built in December. Murray steel buildings did it...done a great job. A friend did the road and poured the slab. 

 

Mine is the uninsulated version, it's got an anti condensation lining on the roof panels. Works well and I love it. 

 

Less than 4m apex height and 30m2 you don't need planning in Scotland. Mine is less than 4m apex...but the area might be over 30m2......

 

 

[jamieled]

Thanks all, some interesting ideas.

 

Planning/building regs is pretty clear for what we're trying to do. There is an exemption from full planning for sheds up to 280m2 which are for forestry/agricultural purposes. Prior notification is required though. Building control/warrant is not required so long as it is single storey and below a very large footprint threshold which we're not near (again related to forestry/agri exemption).

 

Including an office in the future would technically need planning and BC due to the change of use (I think), hence thinking it through now to make sure we don't prevent ourselves from being able to do that if we wish.

 

Like the idea of a heated workshop!