Foundations required for French Doors?

[MiyaMIck64]

Hello members, newbie alert, first post.

I've browsed this forum a few times now for answers, always useful!

I have a covered storage area that I want to make more useful annex/office, essentially it’s like a garage built between two existing properties, with a room over the top – old wooden garage doors at the front and open to the elements at the back. I plan to add an arched window with French doors into the open gap at the rear, and then line the whole thing out and add joists/new floor etc.

I think I’m likely to need foundations of some kind for the frame of French doors to sit on, the question is how deep I would need to go – I guess it’ll need to take the weight of a timber frame with double glazed doors etc. but the main structure of the building/s already exists.

I have a reasonable amount of practical ability and understanding.

Any suggestions very welcome,

Thanks,

Paul

 

[Ian H]

Would you want a concrete foundation then a few course of engineering bricks and a DPC under the doors?

 

[MiyaMIck64]

Hello,

Yes I’m wondering if that’s what I need, but how far to go down. I'd need to dig a trench across just inside the arch. At the moment the patio stones continue through from the garden area right through the garage to the front of the house - they run downhill. The patio stones will be finished just below (or around) the level of the internal finished floor level – the garden floor will be levelled out. I’ll obviously need some drainage in front of the proposed doors too.

Cheers,

Paul

 

[noseall]

Your foundation will need to be standard i.e. down to good ground and usual 200mm+ thickness.

 

[MiyaMIck64]

Thanks both,

That’s what I’ll do then, just wanted to check I’m doing the right thing. I think the foundation under the doors will be the hardest graft, the rest I think will be joists spanning across, some DPM and a stud wall.

Cheers,

Paul

 

[^woody^]

The weight of the doors is on the walls ether side of the opening, and not on the wall below it. However you need a foundation down to ground that is suitably firm and stable.

Wall foundations will need to be as deep as the main house foundations - about 600-750mm down normally, and twice as wide as the wall you are building on them.

The foundation under an opening can be less deep - about 400mm, but it may not be practical to do this, so a single foundation just goes across the whole lot at one depth.

You can fill the trench with concrete and have a few course of bricks up to the finished floor level, or you can put 200mm or so of concrete down and then build the wall.