Raising the ground floor

stringbean

Hi,
We have the foundations in, were put in a few years back to maintain planning permission (we're based up north). We are now ready to build and one of the changes we decided upon was to raise the existing foundations by approximately 4 foot in order to improve the view.

We have been to couple of builders and had conflicting views. One builder feels that we will need substantial hardcore fill to raise the ground around the site whilst another felt we could use the ample soil we have available to raise the ground floor level.

Just wondered if anyone on here had raised their site in a similar way and what they did.

Thanks for any advice!

4Sticks

If you set the floor slab very high off the grade ( the existing site level) you will need an engineered solution.
Filling alone with any materiel will not be adequate and your floor slab will sink - bet on it.
In the ROI you would be tied to the level stated on your planning drawings. Raising by 4 foot would see you in major trouble.

Drift

4 foot is a lot in this context.

What type of foundations do you have in OP? Structural advice is not allowed here we might be able to give you some general thoughts with a bit more info.

BryanF

stringbean wrote: »

Hi,
We have the foundations in, were put in a few years back to maintain planning permission (we're based up north). We are now ready to build and one of the changes we decided upon was to raise the existing foundations by approximately 4 foot in order to improve the view.

We have been to couple of builders and had conflicting views. One builder feels that we will need substantial hardcore fill to raise the ground around the site whilst another felt we could use the ample soil we have available to raise the ground floor level.

Just wondered if anyone on here had raised their site in a similar way and what they did.

Thanks for any advice!

Speak to your architect/engineer

suspended timber floor- factor in suitable thermal bridge detailing, air-tightness and sub-floor ventilation.

stringbean

The foundations are strip foundations.

We consulted with the architect at the time and he felt this should not be a problem and did not mention any structural changes required.

The house itself is built on very good ground.

Drift

In general terms something like that would probably be possible in a couple of ways but you will need to get an engineer to design it for you:

1. Deeper rising walls combined with an engineered/designed fill material and cast in situ ground floor.
2. Retaining/rising walls holding back the exterior fill combined with a suspended floor in either timber or concrete.

You will need to get an engineer to design the foundations and specify the different fills and compaction regimes in different parts of the site. Wall structure, ventilation, air-tightness, damp-proofing, etc. would all need to be carefully addressed.

I am not familiar with the rules in the north but it would be considered a very serious planning issue down here to raise the house be 1.2m from the level you were given permission to build it at.

Drift

N.B.:

It is important to realise that there are different considerations and qualities of material required when raising the ground level in your garden to raising the ground level underneath your house.

I'm sure you knew this but the way one of your posts is written makes it a bit unclear!

4Sticks

You will pay handsomely too to shift suck muck around

stringbean

Drift wrote: »

In general terms something like that would probably be possible in a couple of ways but you will need to get an engineer to design it for you:

1. Deeper rising walls combined with an engineered/designed fill material and cast in situ ground floor.
2. Retaining/rising walls holding back the exterior fill combined with a suspended floor in either timber or concrete.

You will need to get an engineer to design the foundations and specify the different fills and compaction regimes in different parts of the site. Wall structure, ventilation, air-tightness, damp-proofing, etc. would all need to be carefully addressed.

I am not familiar with the rules in the north but it would be considered a very serious planning issue down here to raise the house be 1.2m from the level you were given permission to build it at.

Drift
Thanks for your help. Just to confirm we got planning permission to raise the ground level

blacktea

I would think block and beam would be a good option myself rather than having to raise ground levels / large amounts of fill.

obviously if external ground level is raising, some form of drainage solution to prevent water logging underneath the floor would be needed.

q the engineer...