rotten chipboard subfloor

[zipdoodah]

Hi all
We were taking up some tiles today to make room for our new washing machine! The tiles were laid on ply, which was laid on the chipboard subfloor. House is an early 1990s build.
We moved in 2 years ago and were told there had been a considerable leak in the utility room but it was fixed (our surveyor didn't even raise it as a prob).

On lifting the tiles this morning we realised that the chipboard is still wet! Its actually rotten in places and needs to be replaced. Luckily its only one sheet of board that is damaged. But I was imagining needing to replace joists as well. But we can't find any! It seems the chipboard is laid on polystyrene (which is covered in a black damp proof sheet). Its not even secured under the skirting, which we've also removed. I've never lived in a house this age before - how do I replace the chipboard if I can't secure it to anything? I assume the polystyrene is just laid on a concrete base.

Thanks

 

[TonyW2]

You have a floating chip board floor on king span insulation on a solid concrete floor.
No joists so an easy replacement. Make sure that its dried out and any other wet areas with rot replaced. You could glue the t & g joints. If retiling on a floating floor you must use flexible grout.

 

[zipdoodah]

Thanks for the advice. Turns out that chipboard is a freaking sponge and several of the pieces of floor need to come out. Plus my damp meter tells me the plasterboard needs to come off the wall to about a height of 1ft (its just a cheapo one but its served me well in previous houses). Anyone got any experience of how long to dry the room out before replacing the floor, replastering etc. Its about 5ft by 10ft, theres no radiator. We've got 2 small fan heaters & a domestic dehumidifier. I'd be grateful for the advice.

Also there's black plastic sheeting separating the chipboard floor and the polystyrene insulation. Is this a good thing ot a bad thing... can't help but think its the plastic that means the water had nowhere to go other than to stick in the chipboard!

Thanks again.

 

[dann09]

A 1990's house would possibly have a screeded block and beam floor.

Or, if its a true concrete slab, then the slab will have a DPM(membrane) and insulation below.

What does the bottom plate of the studding sit on?

Perhaps you would do well to lift all coverings to expose the screed you mentioned. If the screed is in bad nick then come back here - with a pic if possible?

What material do you want as a finished floor? Tile or laminate etc?

 

[IJWS15]

If you have been in for 2 years then there is still a leak. Find it before replacing anything.