concreting a floor

[david1805]

Hi all,

I have an outside loo on the end of the house which I want to convert to an inside loo. My question relates to the floor.

Currently its blocks laid on a bed of sand laid onto earth.

How deep should I dig this out to be able to concrete it?

Having dug it out do I just lay a membrane on the earth before pouring the concrete?

 

[michaelc]

you need to dig down through the earth tiil you reach firm ground , i would go down 12inches ,throw in 4 to 5 inches of hard core ( broken bricks ,blocks , lumps of stone ,concrete . compact this somewhere near to a flat level with a heavy hammer , then spread about 2 inches of soft building sand over the hard core and make it fairly level this is called blinding and it is the base for your membrane to lay on , i would double or even treble the thickness of the membrane to prevent damp . make sure the sides of the membrane are left longer than you need ,so they come up the side of the new concrete base and are still visable when the concrete base is done , 4 to 5 inches i would say , this is so you can lay a floor screed on to the top of the concrete base and are still protected by the membrane .as for the concrete base its self look to lay about six inches of concrete and include some reinforcing rods halfway up the base no lower or higher , you can sit the bars on little brick or blockl pads so the concrete will run under the bars when you pour it in . last but not least make sure you measure down from your existing floor level so you leave the top of the concrete base at the correct height so as to allow the correct amount of screed or floor tiles to run level with your house floor level

 

[david1805]

Many thanks for a very comprehensive reply!