New Conservatory; How deep should foundations be?

stuart45

Phil4432 said:

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.

It depends on how wide the walls are. For a 300mm cavity wall with a trench fill foundation 600mm would be normal. In a trench with only 225mm concrete at the bottom the trench would need to be wider to allow the bricklayers room to work.
It's possible your neighbours had a wide strip foundation which is sometimes used in soft ground. It needs rebar at the bottom.

Section62

Phil4432 said:

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

Wondering if it would be worth getting an architect in.

When you mentioned the platform and retaining wall I started thinking 'structural engineer' - but I wouldn't say you definitely need one without knowing more about the situation.

If you do need professional advice I think it more likely a SE would be the appropriate input here, an architect will probably need to call in a SE anyway, unless the job is more straightforward than it sounds.

stuart45

I probably wouldn't call an architect for that. An SE as Section62 said would be better. You might be able to get some info from your local BCO. Even though most conservatories don't require regs for foundations, they might well offer you some advice as they will know the local subsoils.
You neighbours might also help. 
Conservatory foundations are often inadequate, so it's worth doing the job properly.

Phil4432

stuart45 said:

Phil4432 said:

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.

It depends on how wide the walls are. For a 300mm cavity wall with a trench fill foundation 600mm would be normal. In a trench with only 225mm concrete at the bottom the trench would need to be wider to allow the bricklayers room to work.
It's possible your neighbours had a wide strip foundation which is sometimes used in soft ground. It needs rebar at the bottom.

I'll explain my ides for the Conservatory; the windows and glass roof are actually in good shape.  A couple of years ago I proposed to a couple of local companies that they build exactly the same walls as the existing walls, but with new foundations, and reuse the windows/doors again.

One company refused, another said he would do it.  I'd then have to check their guarantee and what they would cover; if the lifting and re installing of the frames were to cause a leak I'd want that to be under the guarantee. 

The neighbors extension had trench foundations, 1m deep and 1M wide.

With regards to the depth of the foundations of the houses, going by the neighbors exaction I would say that they at least 1M deep.  These houses have a space underneath the ground floor, with enough room to stand up in.  Almost like a cellar.

However, if the foundation of the house were to prove to be less than 1m, and the new foundations for the Conservatory 1m deep, there may be a need to underpin the foundations of the main house.  I'd rather not do that.  The depth of the foundations of the main property, will also determine whether there is a need for a Part Wall Notice or not.

Probably best to get a structural engineer in!

Phil4432

stuart45 said:

I probably wouldn't call an architect for that. An SE as Section62 said would be better. You might be able to get some info from your local BCO. Even though most conservatories don't require regs for foundations, they might well offer you some advice as they will know the local subsoils.
You neighbours might also help. 
Conservatory foundations are often inadequate, so it's worth doing the job properly.

The council don't offer much advice on Building Control anymore; you get referred to a private company who aren't very helpful.

Looking at this link, it says that Conservatories are normally exempt from building regs but doesn't mention anything about foundations.  Something else to check before work commences.

stuart45

Phil4432 said:

stuart45 said:

I probably wouldn't call an architect for that. An SE as Section62 said would be better. You might be able to get some info from your local BCO. Even though most conservatories don't require regs for foundations, they might well offer you some advice as they will know the local subsoils.
You neighbours might also help. 
Conservatory foundations are often inadequate, so it's worth doing the job properly.

The council don't offer much advice on Building Control anymore; you get referred to a private company who aren't very helpful.

Looking at this link, it says that Conservatories are normally exempt from building regs but doesn't mention anything about foundations.  Something else to check before work commences.

Foundation's aren't part of the regs for most conservatories. 
Our local BCO's are usually pretty helpful, although it probably helps that I know them. Maybe some of them have stopped answering questions to people who just phone in for advice.