Foundations for steel framed workshop?

[Agrismith]

Where I am, a temporary structure is marquee or similar tent like structure. The separate sheds are compromise but one I think I can work with. I did have planning for a larger single building but one of the conditions was that it must be built of natural stone to match the main house and surrounding buildings. I simply can’t afford to build it.

You can get stone effect composite cladding panels that meet planning requirements. At a vastly reduced cost

 

[Hooflungdung]

Pad and strip foundations for the under build with separate floor slab. Using a continuous slab between the two buildings will be a nightmare to keep the water out.

Central prop on a portal frame does little to the lateral load at foundation level. They’re more used to reduce the rafter size on larger spans so you’ll need account for this in your base / foundation design. You’ll also need vertical bracing on the longitudinal direction if it’s just a steel clad box you’re building.

I would be surprised if your local authority would accept the proposal as being two separate buildings given their proximity and size though. Best seeking advice from local planning before sinking a load of money into them. A pre-app can be useful for these type of things.

Perhaps I am misunderstanding where, or what, the lateral loads are coming from, and in what direction they are applied.

A single 60+m2 building under 2.5 max height meets the requirements of PD. I’m not sure why you would think the LA wouldn’t allow two smaller buildings next to each other on the same footprint.

However, I do know a planning appeal inspector so will ask for her point of view.

 

[Hooflungdung]

You can get stone effect composite cladding panels that meet planning requirements. At a vastly reduced cost

Thanks. Sadly, they won’t do. It has to be local ironstone.

 

[Pigeon_Droppings2]

A single 60+m2 building under 2.5 max height meets the requirements of PD

Where I live there is an additional constraint on the proportion of your plot that's been developed too...worth checking.

I have a concrete sectional garage and that's on just a reinforced raft (pad)...we are also on clay. The roof on mine is just steel sheet which I think keeps the weight/loads down quite a bit.

 

[knighty]

Don't trust or have any faith in planning!

We want to knock down out garage plus attached outbuildings, then knock down a separate workshop and rebuild bigger

Told us we could do the garage under permitted development... so we knocked it down... now they changed their mind and said we can't rebuild the garage because its too big... even tho it's the sane size of the stuff it's replacing.

 

[Hooflungdung]

Where I live there is an additional constraint on the proportion of your plot that's been developed too...worth checking.

I have a concrete sectional garage and that's on just a reinforced raft (pad)...we are also on clay. The roof on mine is just steel sheet which I think keeps the weight/loads down quite a bit.

Yes, half the area of the garden minus any other outbuildings. I’m not even close on that score.

I assumed a raft type slab would be best on clay as it can move around without the building falling down. Not that that is likely to be an issue with a steel framed and clad structure.

 

[Hooflungdung]

Don't trust or have any faith in planning!

We want to knock down out garage plus attached outbuildings, then knock down a separate workshop and rebuild bigger

Told us we could do the garage under permitted development... so we knocked it down... now they changed their mind and said we can't rebuild the garage because its too big... even tho it's the sane size of the stuff it's replacing.

I included the demolition of our existing garage in the planning app for the larger new garage. They hit me with a bat survey request. £2k and no way round it that I can see.

The daft thing is that I subsequently discovered that I didn’t actually need planning permission to demolish the existing garage.

 

[KaneH]

Perhaps I am misunderstanding where, or what, the lateral loads are coming from, and in what direction they are applied.

Wind load, acting on all directions depending which way it’s blowing.

 

[Pigeon_Droppings2]

I assumed a raft type slab would be best on clay as it can move around

I think the way it works is it "floats" by spreading the building load over a much larger area.

Have you tried chat gpt?...give it your design and situation and see what it suggests (it can even look up soil conditions!). Not saying just build what it says...but would allow you to get a rough idea.

 

[Hooflungdung]

I think the way it works is it "floats" by spreading the building load over a much larger area.

Have you tried chat gpt?...give it your design and situation and see what it suggests (it can even look up soil conditions!). Not saying just build what it says...but would allow you to get a rough idea.

Now that is certainly something I haven’t considered. Thanks.

 

[addjunkie]

Don't trust or have any faith in planning!

We want to knock down out garage plus attached outbuildings, then knock down a separate workshop and rebuild bigger

Told us we could do the garage under permitted development... so we knocked it down... now they changed their mind and said we can't rebuild the garage because its too big... even tho it's the sane size of the stuff it's replacing.

For what you are proposing put the lot through planning, then no arguments

 

[Maxakarudy]

If I was building this I'd put down a 6" slab with reinforcement, but build it entirely from 100mm insulated roof panels, walls inc.
It will be quick & easy to build, used panels are even cheaper, but will have a few extra holes in, but a rivet will fix that,
I've just built a garage/spraybooth that way myself 9mx5mx2.5m onto an existing slab, inside an existing building, there are no load points to deal with

 

[Agrismith]

If I was building this I'd put down a 6" slab with reinforcement, but build it entirely from 100mm insulated roof panels, walls inc.
It will be quick & easy to build, used panels are even cheaper, but will have a few extra holes in, but a rivet will fix that,
I've just built a garage/spraybooth that way myself 9mx5mx2.5m onto an existing slab, inside an existing building, there are no load points to deal with

To pass building control you have to account for snow load so will have point loading. You will also have to account for wind loading so those panels will need a steel portal frame behind them when used externally. So you will definitely end up with point loading for external use.

As for raft v pads. A raft will spread the load but each situation is different so you would have to see structural engineers drawings as to which is more economical. A bit of extra concrete for pads can often be cheaper than the labour involved in installing the reinforcing in a raft with thickenings, depending on the reinforcement design. If they want a lot of cut and bent bar into the thickenings then concrete pads will be cheaper, especially if you want to tackle some of it yourself.

 

[Maxakarudy]

I'm not a structural engineer & if it was externally built I would get the calcs done just for b/c, but the weight & strength of a 100mm insulated
panel wouldn't require a portal frame, just some 3mm 100x100 angles to corners, roof, slab & wall connections, just my opinion, a 100m panel is structural imo.