Damp, particle board and bearer/joist spacers

In my (newishly purchased 9 months ago) Sydney (Randwick) terrace, the floor in one of the ground floor rooms recently started to sag at the edges. I couldn't get access under the room so eventually I bit the bullet and cut in a pretty amateur trap door...(my first circular saw job, oh dear!)

Underneath I found a very damp room, with some still water in one corner where the floor had dropped the most. The room looks like it was re-stumped and new joists and bearers put in, probably about 10 years ago. The floor has T&G particle board down with a cheap T&G floating floor above it.

The drop in the floor seems to be caused by two damp related problems

1. The particle board has decayed in a number of areas, I actually got fanned vents put in which I think has significantly dried out the underfloor, causing some bits of the particle board to collapse

2. On top of the stumps, between the bearers and the joists, there were some spacers made out of chipboard, these have also decayed and consequently the joists resting on it have dropped by about 5mm.

To tackle this I intend on

1. Figuring out where the water is coming from and stopping it!
2. Replacing the spacers between the joists and bearers
3. Replacing the damaged particle board
4. Re-laying the floating floor that has sunk


The advice I need is as follows (thanks!)

1. What shall I use for the spacers? I only need to lift the joists back up by about 5mm. I am hoping I can get away with doing this without having to take all the joists out, so maybe a wedge of some sort hammered in and then fixed with some nails?

2. I suspect that the water may be due to the house being on a natural water course (on sand stone). Can you get a moisture resistant substitute for the T&G particle board used?

3. The T&G floating floor laid over the particle board was laid in-line with the joists rather than perpendicular. Is this normal? (i.e is it assumed that the particle board is strong enough so you don't need to worry about strength from the floorboards on top)?

Thanks in advance to anyone who can help!

Regards

Mark

G'day mark, your plan sounds good. If the flooring is a floating floor you may be able to take it up and reuse it. This is because some don't ude glue for the joints. Just out of interest did you get a building inspection?

I would;

1. remove existing flooring.
2. find source of water and fix it
3. insert more subfloor ventilation +/- fans
4. repair broken stumps, joists and bearers.
5. use fibrecement spacers eg villaboard
6. relay flooring of choice

cheers
pulse

Thanks for the reply, I'll look out for some villaboard. I did have an inspection and he did tell me the place had some damp, but he couldn't get into that particular room.

I added the vents which seem to have resolved the air flow issues, just need to work out where the bloody water is coming from!