We’ve recently moved into a 1995 built detached house with an integral garage. Washing machine has been leaking in the garage so I’ve removed the boxing from around the internal soil stack and sorted the leak.

I’m now left with a hole in the floor around the soil stack. The previous boxing in was far larger than it needed to be so I’d like to patch the v ncrete floor before some tighter boxing.

Question 1. How much damage is the leak likely to have done assuming most of it went down the hole?

Question 2. What’s the best way of repairing the floor and what do I need to consider?

No damage. Water will have gone down the void under the floor. Fill the gsp in concrete.

Your floors are beam and block construction

C

Lag soil pipe with loft insulation when you rebuild the boxing. This will help deaden the noise of the water when the toilet is flushed.

You could also wrap some foam around the pipe before you concrete to form an expansion gap to prevent any damage in the future if there is any movement (although this would be highly unlikely).

Thanks. I’d considered that I might need something to stop the concrete sticking to the soil pipe and act as a bit of a buffer.

I can’t detect any sort of damp proofing membrane in there. Do I literally just mix a bucket of concrete and pour it in then?

If you just chuck concrete in you could well end up needing a couple of lorries worth as you’ll end up grouting the floor void. I’d be tempted just to pack it out with some kind of mineral fibre, as you may need to get at it again in the future.

I’d make up a couple of pieces of of thick chipboard or solid wood up to fit either side and make up packing to fit under to get the right height.

If you are concerned about gaining access in the future, you could fill the main void with polystyrene leaving it about 10-15mm from the floor level and simply top up with self levelling compound or grout.

IN A FLOOD SITUATION WATER WILL ALSO RISE OUT OF THE VOID.SEAL IT

In a flood water will be running under the garage door at about the same time should he seal that too? Seriously though, the sanitary space under the house has all sorts of stuff running through it and many holes up into the house.

See the edge of the washing of the picture? I want to be able to stack that and the tumble dryer close to the soil stack. I just need something firm and stable enough for the washing machine really.

Expanding foam to pre fill the big gaps around the pipe as it goes through the floor void at block level. Then as above a simple collar of myothene or similar around the pipe before reconcreting which is just good practice.
And I’d try and get a bit if polythene down on the block if you want to be really picky.

“IN A FLOOD SITUATION WATER WILL ALSO RISE OUT OF THE VOID.SEAL IT”

Wow ?

Thanks folks. Off to the diy store for supplies then I guess.