I'm a novice; how to lay a floor over concrete?

[Windrush]

I'm a DIY novice and looking for advice on how to lay a floor over concrete.

Some years ago, the attached garage was converted to a kitchen. We recently had some water damage from a leak in the bathroom above it; the pipe connecting the bathroom sink to the wastepipe was leaking down the outside of the wastepipe and into our kitchen.

It looks like the person who laid the current kitchen floor put down a plastic sheet (it's not a proper damp proof membrane, it's just a thin clear plastic sheet) over the concrete, then screwed 1" thick chipboard into the concrete and then put the laminate kitchen tiles on top of that.

We're trying to do all of the work ourselves because we can't really afford to hire someone to do it but we want to make sure that we do a proper job of it.

How do we sort out the kitchen floor? I assume that we need to put down damp proof membrane, how do we lay that properly? What do we put on top of it after that, chipboard?

 

[mknott]

im no expert on it however when i put laminate flooring on concrete i had to put down a plastic layer first and then the underlay on top of this followed by the laminate flooring.

 

[Windrush]

Thank you.

Can anyone else give some more experienced advice?

We haven't decided what material we're going to use to lay the floor; currently we're considering another kitchen laminate or sheet vinyl.

I just need to know if we need to lay a damp proof membrane on top of the concrete and how we lay it (e.g. does it have to go up the walls and overlap the damp proof course?). Then we need to know what kind of sub-flooring to use - chipboard, plywood? Do these have to be drilled into the concrete?

 

[dazlight]

How old is the subfloor in the kitchen mate?
does it have a SDPM ( sheet damp proof membrane ) under the concrete do you know.

 

[Windrush]

I'm not sure how old the subfloor was. It had to come up regardless, though. It was chipboard and damaged by the water. It was just falling apart.

I don't know if we have a DPM under the concrete. The house was built in the 70s, and I assume they followed whatevet the building regs were at the time but I have no idea what those would have been.

 

[dazlight]

I wouldn't put ply down again mate. As any rising moisture would effect the ply. Think you be best doing a damp test then screeding the floor with a latex screed or water mix. Using a good screed like f.ball, laybond, mapei, ardex or uzin. If you need a dpm you could use a liquid surface dpm or get the floor asphalted.

 

[Windrush]

Is it essential to screed the floor?

I didn't know what it was but I Googled it and, from what I can understand, we would need to get someone in to do that for us (for it to be done properly anyway). We're trying to do all of the work ourselves, if possible, to save money and we're novices.

When we removed the old chipboard, there wasn't any evidence of rising moisture. The chipboard that wasn't affected the leak was completely dry and that chipboard had been down for at least 6 years (that's how long we've been in this house) and probably longer than that.

I think the reason that they laid it was to elevate the floor because there is about an 1½ inch height difference between the cement floor and the floor of the room next to it.

Would there be anything wrong with laying a sheet of DPM and then putting ply down on top of that (screwing it into the cement), then putting down an underlay and then flooring?

 

[dazlight]

If the sheet is to act as a dpm then if you screw through it it will be full of holes so won't work. You will prob be ok loose laying the boards if heavy enough. I'm just talking from a floorlayers view.
Screeding isn't that hard if you have the right tools. So you could do it correct. It's just about buying the right screed.
You would need a good trowel and a spike roller, you should be ok then as it won't need to be perfect because your not sticking any flooring to it.
Alot of screeds flow really well now so alot easier then 10 years ago.

 

[Windrush]

I appreciate the advice! I just don't have the confidence to do the screeding myself.

If we were to lay a DPM and then loose lay boards on top of that, are there any problems that could arise from that? If so, what is the likelihood of that occuring?

Would condensation form between the DPM and the boards? Would the boards shift considerably if they weren't secured to the concrete?

 

[dazlight]

The dpm sheet should stop any damp rising upto the boards. If the floors not level the boards may move which could cause problems with the new floor.
I can do it the same way as last time an screw through the sheet and might be ok.
I'm just saying long term the correct way is too screed the floor.
The thicker the ply the less chance of the boards moving.
But if after 6 years of no damp in the chipboard I think you will be ok.