Concrete floor

[ms2004]

Hi, some advice please. Our house is a U shape so at the back we have 3 external walls which would be ideal for an extension in between. The space between the walls is about 12 m3. Coming through the space is a soil pipe which ties into a manhole. The manhole is outside the footprint of proposed extension. The soil pipe would be beneath the floor of the extension. From looking in the manhole the depth of the pipe is about 150mm. I was thinking about having 22 chipboard on 45 runners over a concrete slab but that will mean I’m not able to get the slab to a thickness of 100. The slab would end up being about 80 thick. The extension will be single story flat roof.

Also my foundations will run directly across the path of the soil pipe. Moving the soil pipe is impossible so the soil pipe will run through the foundations. Any foreseeable problems with either of these scenarios?

Thanks in advance

 

[^woody^]

No

 

[Ian H]

150mm deep?

 

[Billy Matthews]

I'm not an expert in this area so take what I say with a pinch of salt. As long as the soil pipe is owned and controlled by yourself and no one else is ever going to need access you wont have a problem there. As for the weight of the extension on top it may be worth consulting a specialist in the area to see if the slab could cause damage to the pipe, maybe get a CCTV survey done on the condition of the pipe to double check. The last thing you want is to tare up the slab after it's down.

As for the slab it's self 80mm seems a bit thin for a foundation but that's where a structural engineer and building control would come in handy.

Anyway keep us updated, I would be interested in finding out the result of what you find.