Existing Ground Floor - Extend to first floor

[KatieDUK]

Hello,

The house I am nearly completed on has a downstair extension from the 90's. I wish to build above this for an extra bedroom. There are no building control docs or drawings so I have no idea about the foundations. I really don't want to knock it down to start again if can help it. I also wish to extend this downstairs extension too. Obviously the ground floor addition that I will add I will ensure foundations will support another storey but what do I need to do to support the first floor otherwise? I am likely to make the downstairs extension before starting upstairs.

The existing extension is sandwiched between next door and existing house so once I build the additional part downstairs the original foundations won't be accessible.

Please help, this is all new to me!!

 

[jeds]

Can you post a photo or two.

Going back to the other thread - about the garage; garages built with the main house are nearly always the same foundation as the house. But you can't say that for an extension, because you don't know who built the extension or to what standard it was built? To build above, the foundation will need to be checked. That means digging a hole at the base of the extension down to the foundation. You are looking for the width and depth of the concrete, the depth that the concrete is sat on and the condition of the soil it is sat on?

If you follow the wall down to the foundation, when you hit concrete there should be a lip of concrete at the base of the wall - a bit like a shelf. The width of that shelf will indicate the overall width of the foundation. Generally you are looking for something about 150mm wide - but it might be a bit less?

Then dig on down to the base of the concrete - how deep is the base of the concrete from ground level and how thick is the depth of the concrete.

If you get to 1200 or 1300 deep and the concrete is still going you've seen enough. It will be ok.

 

[KatieDUK]

Thank you for taking time to reply. My concern is if I build the utility room over the next few months (which will be to the correct foundations ) how will building control every check the old part of the extension when it is fully blocked in on all sides?

 

[jeds]

Check the foundation before it is blocked in?

 

[KatieDUK]

I would for my own piece of mind but wouldn't building control need to see before we started the upstairs extension in a few years time?

 

[jeds]

The safe route is to make the building regs application and have it inspected now. Keep photos etc. and clearly record, and confirm by email, the inspectors visit. You then just continue with the first floor project when you are ready. A bit long winded but ok as long as you are sure you will carry on with it.

In reality you should be able to just inspect and record the foundation now - keeping photos and records etc. - and then make the application as and when you get started. Problem is you run the risk of getting an inspector who is a bit short on common sense. They are about.