New Conservatory; How deep should foundations be?

Phil4432

So our old Conservatory is coming to the end of its natural life.  It was built by Astral on crappy 30CM footings which proved to be inadequate; especially on soft clay.  It came with the house, and is around 14 years old.

I'd like to make the new Conservatory as durable as possible, and was wondering how deep the foundations should be.  A quick online search seems to suggest that they should be 90CM-1m deep on soft ground.

Any opinions welcome as always.

stuart45

Going down 1000mm in clay soil would be a better foundation.
Are there any trees close by?

markin

Only 14 year old, don't use Astral again.

How deep is the house foundation...

Phil4432

stuart45 said:

Going down 1000mm in clay soil would be a better foundation.
Are there any trees close by?

Agreed on 1,000cm.  There's a small tree about 2-3 meters away from the existing conservatory; the garden is on a slope so the conservatory is on a raised platform, with a retaining wall.

aoleks

1m will do.

Section62

Phil4432 said:

stuart45 said:

Going down 1000mm in clay soil would be a better foundation.
Are there any trees close by?

Agreed on 1,000cm.

10m would be much too deep.

Phil4432 said:

There's a small tree about 2-3 meters away from the existing conservatory; the garden is on a slope so the conservatory is on a raised platform, with a retaining wall.

Raised platforms and retaining walls complicates things.  It would be better if you could post a picture of the existing arrangement so we can get a better understanding of the situation.

Section62

aoleks said:

1m will do.

It needs to be better than "will do" if there have been problems in the past.

stuart45

You never really know for sure until the foundations are dug out.

Phil4432

markin said:

Only 14 year old, don't use Astral again.

How deep is the house foundation...

Really not sure re house foundation.  Standard 30's s bed semi.  Would never use Astral and absolutely do not recommend them.

Phil4432

Section62 said:

Phil4432 said:

stuart45 said:

Going down 1000mm in clay soil would be a better foundation.
Are there any trees close by?

Agreed on 1,000cm.

10m would be much too deep.

Phil4432 said:

There's a small tree about 2-3 meters away from the existing conservatory; the garden is on a slope so the conservatory is on a raised platform, with a retaining wall.

Raised platforms and retaining walls complicates things.  It would be better if you could post a picture of the existing arrangement so we can get a better understanding of the situation.

I'll try and do a diagram, would rather not post home pics.

Wondering if it would be worth getting an architect in.

Phil4432

stuart45 said:

You never really know for sure until the foundations are dug out.

Any idea of what the width of the foundations should be?  Our neighbours had foundations 1M wide for their extension, am wondering if this would be overkill for a smaller conservatory.