Outbuilding floor below ground level

[perky416]

Hi guys.

I want to build an outbuilding with the external dimensions to be within permitted development (2.5m overall height, less than 50% of land surrounding the house, less than 30sqm), however i intend to have the floor 450mm below the external ground level, so you will step down into it, to make an internal height between floor and ceiling of around 2.6m.

Would this still fall within permitted development? I cant find anything to suggest otherwise.

Are there any other regulations etc i need to he aware of when doing this?

Thanks

 

[John D v2.0]

It's the height above the ground level immediately beside the building that matters.
Although if you start digging down further then a nominal amount you would need building regs and maybe planning permission as it turns into something major when it's effectively a basement.
If it is important you can always apply for a lawful development certificate, but if you're not selling up or likely to attract complaints then there's not much benefit.

 

[nickjb]

Any reason to think you wouldn't get planning permission for a taller building? Mine is 3m high and it went through planning permission without a hitch. Surely it'll be cheaper, easier and better once finished. If it gets denied you can still fall back on your current plan.

 

[perky416]

Any reason to think you wouldn't get planning permission for a taller building? Mine is 3m high and it went through planning permission without a hitch. Surely it'll be cheaper, easier and better once finished. If it gets denied you can still fall back on your current plan.

Cost, time, and looks.


Cost - We are trying to keep build cost to a minimum. To keep it watertight people here have recommended DPM between 2 courses of blocks which wont cost a lot. The only additional cost incurred with going down vs up will be the grab hire to get rid of the soil. When you factor in architect, structural engineer and planning costs i imagine a couple of grab hires will be cheaper.

Time - we want this done asap. Dont really want to wait for planning permission.

Looks - my neighbours garage stands 2.5m tall, and this will be built right next to it. To get the height i need, id also have to go to about 3m. I think it will be a bit of an eye sore if it was 0.5m taller than the neighbours. Plus im trying to no block the light from my other neighbours garden.

 

[mrrusty]

Any reason to think you wouldn't get planning permission for a taller building? Mine is 3m high and it went through planning permission without a hitch. Surely it'll be cheaper, easier and better once finished. If it gets denied you can still fall back on your current plan.

+1

When you factor in architect, structural engineer and planning costs

?? The planning costs are the fee - £200ish depending on area plus a couple of downloaded plans for site plan and location e.g. https://www.ukplanningmaps.com/site-plan - for PP you only need hand-drawn sketches to scale of plan and elevation - planning is only interested in form and function - they don't give a monkeys about structural issues. You don't need an architect and structural for a garden room!!

this got planning (not mine)

and here's my garden room in progress with planning permission

 

[freddiemercurystwin]

The OP want's to keep the height down to 2.5m, he's written other threads showing the location of the building and the context and reasons for needing the height inside.

 

[mrrusty]

The OP want's to keep the height down to 2.5m, he's written other threads showing the location of the building and the context and reasons for needing the height inside.

Y I know, and the idea of inexpensively DIY building with a finished floor 450mm below ground level, which means taking out 600mm+ of soil - a huge amount - and without building a swimming pool is challenging to say the least . Perhaps it's different where the OP is, but where we are if I dug out 20sqm+ @ 600 deep it would be a foot deep in water PDQ with groundwater and run-off. It's one thing clearing a trench of water enough to pour a footing, and quite another to clear several tons of water to start building an underground concrete pad, and at the same time keep it all watertight while you build the blockwork up.