Self levelling compound over chipboard?

[Rutz]

Hi,
I've read the wiki and a few posts regarding usinig SLC but am a bit confused so would like to confrim a few things.

I'm in the process of replacing my floor (1930s house, ground floor). The previous owner had removed the chimney and so the floor consited of a badly patched concrete area where the chimney had been + knackered floorboards. I will be replacing the floorboards with 22mm T&G chipboard - unfortunatley I didn't read this forum before buying these boards so didn't realise these are spawn of the devil & I should have got plywood instead . I plan to patch up the conrete area so that it is level with the boards. So my questions are:

1) Should I use SLC over the boards/ concrete to gain a completely level surface? I will be laying a floating laminate floor on top - could I get away with just using an underlay? Is SLC OK on chipboard?

2) When using SLC what is the best way to seal up the gaps/holes - ie round the edge of the walls & round the radiator pipes? I thought of expanding foam + silicon sealent.

3) I'm putting in a DPM to prevent condensation problems as I'm fitting Kingspan type insulation between the joists - what is the best way to seal this against the walls. Also what should I do over the ex-chimney area?

Hope you can help!

 

[mattysupra]

you have to lay 4-6mm plywood over the chipboard before you can lay leveling compound.
Do not put any sort of plastic over a wooden subfloor, this will make it sweat and rot the floor.
I would knock out the hearth , then extend the joists and replace with floorboards/chipboard so you have a full wooden subfloor.

 

[Rutz]

Thanks for the reply, but I seem to have confused you. I've pulled all the floorboards up, the chipboard will be screwed direclty to the joists. I thought that if you insulated the floor you had to put a DPM in to prevent condesation.

I'll have another look but knocking out the hearth and putting another joist in sounds like a lot a work - plus I will be putting my HiFi in the room and sitting it on a solid rather than a suspended floor has advantages.

 

[Rutz]

Well this project has dragged on somewhat - mainly because I've been soundproofing a couple of walls.

The floor is now covered in 6mm ply on top of the chipboard and ready for the fball 700. However I mapped out the level of the floor yesterday and there are areas (mainly in couple of corners) that are ~ 20mm from the highest point. I now realise I should have spent longer leveling out the joists but I hadn't bought my laser level at that point Looking at other posts it seems the best way to correct this would be to build the low areas up using additional layers of 6mm ply and then use the fball 700 to level it all out - is the correct?

One other concern I have is that the working time of the fball is ~20min. It looks like I will need 4 - 5 bags so does this mean that I will need to mix up and pour all the bags within 20 mins?

 

[mattysupra]

20 mins per mixed bag. Buy a black dustbin and mix 2-3 bags at a time. You could do with someone mixing the other bags while you are laying the first mixed one so you get a continuos supply up mixed compound.

And yes build up with plywood as you have found in another post which i guess was mine?