Self-levelling over floor boards

[pinnerite]

The restoration of my bungalow has now reached the stage where flooring can go down.

The floors are mostly smooth concrete but the two front rooms are timber-floored. This was probably because it was built on the side of a hill. The front going so low that it would have required masses of concrete to build it up. I cannot be sure but that is the only logical explanation that I can dream up.

However, the passage way leading from the front rooms to the rest of the house has a dip of about 2cm for about two metres in length and < 1 metre in width.

Beneath this are tightly abutted timber floor boards. I had hoped to screed this to level the whole lot.

The carpet company's estimater reckoned it couldn't be done yet I have found several products that suggest otherwise: Mapei Ultraplan Renovation Screed 3240, Ardex FA 20, Sika Latex Ultra and others.

Is he right or am i ignoring the views of an expert?

TIA

[John Rumm]

Normally they suggest a thin sheet of ply well screwed down (random pattern - every 150mm or so) over the boards before applying levelling compound.

[Brian Gaff]

Well, unless you have some bendable cement, it sounds a bit of a tough job for that kind of treatment to me, as its bowed already, putting a heavy very rigid layer on is surely going to bend the floor more. You need the screed equivalent of that denture glue!

Brian

[Andrew]

I would do what John Rumm suggests but use a slightly thicker sheet material so that it ends up a couple of mm higher than the solid part. then self-level the solid part up to the level of the boarded part. Don't put any self levelling stuff on the boarded part at all.

[John Rumm]

That is why the ply is for - to make a suitable base over the boarded bit. It stops the boards bending independently and cracking the SL.

[pinnerite]

No, the floor isn't bowed. The high bit is covered in parquet. Fish-finger sized pieces. The low bit is where they appear to have been removed. The underlying are mature timber, very closely fitted. The products I mentioned are designed to have some elasticity.

I was hoping someone may have used them and coud offer an informed yea or nay. :(

Alan

[Tricky Dicky]

Got to agree with John about a plywood over sheet and the screw spacing too making sure there is no bounce at any point. As for levelling compound use the sort you mix with latex for maximum flexibility plus you can usually apply a thicker coating if required.

Richard

[nothanks]

20mm over such a relatively short distance suggests something underneath isn't quite right. I would lift the boards and investigate - you might be able to fix a problem and remove the need for screed (the longevity of which must be dubious, unless the floor is rock solid).

[Andrew]

A suspended (hopefully ventilated) timber floor is always going to have some movement as we progress from one season to the next. Are there any SL products that can genuinely cope with this ?.

[John Rumm]

Yup there are some specified for use over timber. e.g: