Uneven chipboard floor due to RSJ

[Jinx0879]

Hi all,
We are wanting to lay parquet flooring in our living room, dinning room and kitchen. The issue we have is that the current floor is all chipboard which has slight variation in flatness, but the main issue is that there is a section where the floor seems to fall away after an RSJ, as the floor running through the hallway to the kitchen is at a slight gradient. Will I have to use self leveling compound on the whole area (60sqm)? If so will I need to lay plywood first or is there another solution? The chipboard can't really come up as it is nailed down and goes under all the walls. Thanks

 

[Bonni]

Well yes. If you're not willing to lift the floor, then you will have to self level it or have a wonky floor.

You can always cut the boards on a joist near the walls and self level over the old chipboard where it didn't get lifted/levelled.

 

[Deleted member 174758]

If so will I need to lay plywood first or is there another solution?

From experience I can say that it is far quicker (not to mention cheaper) to build floor levels on uneven flooring like yours with additional layer(s) of plywood, then to build to finish level with an SLC. To do this successfully ideally calls for the use of a laser level and level stick.

Basically you attach the laser to the wall about a metre above the highest point in the room strike a horizontal line. Next take a piece of something like 2 x 1 PSE softwood 1100 to 1200 mm long and draw a line where the laser strikes the stick when it is positioned at the highest point of the floor (obtained by experiment). By moving the stick about the floor and noting the height difference between the laser and the line on the stick (which will show below the laser line on the stick in depressions) you should be able to gauge the area you need to build-up and what thicknesses of plywood are required. Note that when the stick is plumb (vertical) the laser line will be at its lowest point as viewed on the stick

Make sure that you fix the plywood down with sufficient screws - a screw every 100 to 150mm is required. I tend to use drywall screws, which are cheap, but I find that they do need a fast drill (i.e. 3000 to 4000rpm) to ensure that the heads sink under properly. If you use multiple layers of ply it is preferable to glue the layers together (D3 or D4 PVA glue is best). Your parquet adhesive should take out minor discrepancies (2 to 4mm) so absolute flatness isn't necessarily an issue, especially if you take into account the need to sand parquet after installation in any case

 

[Jinx0879]

Your parquet adhesive should take out minor discrepancies

Thanks guys. Would you say it was better to use adhesive instead of nailing the parquet down?

 

[bobasd]

when was the RSJ installed and why?

 

[Deleted member 174758]

Would you say it was better to use adhesive instead of nailing the parquet down?

Parquet is never nailed down, only glued. It requires a special parquet adhesive made for the task (e.g. Lecol 5500, etc) which is flexible enough to allow some movement. It isn't cheap, however. Always leave an expansion gap round the edges of the room (12 to 15mm).