Foundations at my boundary.

[Adrian80]

Hi all,

I am planning on building an extension. However i am a little concerned about the foundations at my boundary.

at our boundary, the neighbour is 1ft higher and there is a small wall ( i assume retaining).

I was wondering when you build on a foundation do you have to build in the centre of it, or can you build at the very edge of it?

cheers for advice

A

 

[Diyisfun]

Well Im no builder, but common sence says you build in the middle, certainly not on the edge.

 

[noseall]

Unless the foundation concrete has been specifically designed for an eccentric load then assume it will sit centrally on the concrete.

 

[Static]

Can build on the edge if you design for the increased loading .. normally means you need wider footing so little to no benefit..

Still not adviseable if it can be avoided..

 

[Adrian80]

Our neighbour has a blockdrive, which would be good not to disturb.

There is no difficulty in making them wider and deeper and our side.

also,

It seems the retaining wall is our boundary. Further back on the same line, our garage is actually built on top of it. We were hoping that we could build right upto the boundary.

I think the retaining wall has been cast, so would chopping off the last 3 inches and replacing it with blocks be feasible. or does this compromise the strength of the wall?

I realise the lack of picture or diagrams is really unhelpful.

A

 

[^woody^]

What if you make the concrete foundation narrower (and deeper) so that the wall is in the centre?

 

[Adrian80]

Yes i suppose this could be done.

I guess your saying the foundation would be as wide as the wall, but the depth would be designed to take such load.

This would make it on the edge both sides in this instance.

ta
A

 

[Deluks]

Single storey extension? is their wall right up to, but on 'their' side of the boundary? or does it straddle both sides? Concrete shuttered wall, brick or blockwork?

If you wanted to build right upto the edge, provided the foundations of this wall are as deep as yours will be, then the wall itself would provide support against your wall overturning. So your foundation would only need have a slight increase in size for you to be able to build on the edge.

You have to take roof overhang and gutters into account. They can't really overhang into next doors 'airspace'.

 

[Adrian80]

I am proposing a double storey extension.

This garden wall is a small retaining wall, about 1 foot high. I think its my side of the boundary.

yeah thought about the roof issues, internal gutters and a parapit wall i was thinking.

A