new possible extension

[topbanana]

A friend is building a patio for which he's putting in strip founds for retaining walls just in case in the future he builds up and extends his house, to the same footprint.
has anyone any experience please of when putting in the floor insulation, 100mm i believe, under the concrete floor slab with dpm etc will this withstand the weather that will hit it.??
also am i right in saying that the base of founds needs to be at least 1m down for a single lift? 600mm wide ? and what min. depth.?

 

[noseall]

pretty mutch all of what you're saying makes sense.
dig down 1000mm, min for foundations, from ground level.
if ground conditions allow, mass fill to within 525mm of the damp course.
remove top soil and vegetable matter.
once the brickwork is up to dpc level then lay;
100-150mm compacted stone or hard core.
50mm sand blinding.
1 layer of 1200gauge polythene dpm, turned up and over onto the brick work.
lay 100mm polystyrene or 75mm celotex, jablite or similar.
1 more cover layer of polythene over the insulation.
lay 100-150mm concrete over site.

 

[joe-90]

I don't think I'd do that. To start with it's a hell of a lot of work for something that you may not need.

Secondly, your building inspector will want to see your foundations should you ever extend. They will need to be 'exposed'. If he considers that the ground needs deeper foundations then you are up the creek without a paddle.

Either build an extension or a patio - but make up your mind before you start.

joe

 

[topbanana]

thanks noseall , very helpful.
i agree with your points joe, however he hasn't got the money to build extension at present and doesn't want to waste time putting something down that involves half the work of the extension only to see it ripped up in a couple of years, perhaps.
i've advised him to speak to the building inspectors before pouring concrete, however , i know from personal experience in cardiff, they don't like something thats 'outside the box'.