Flooring - Replacing chipboard

[David2016a]

Hello,

I am working out if the job of replacing sagging chipboard flooring with new chipboard or plywood is beyond me or not. Not very handy with real stuff as spend most of my time fiddling with computers.

My house was built in the late 80s and some of the flooring is starting to sag a bit upstairs. Speaking to a neighbour who happens to be a retired carpet fitter he told me that its difficult to replace the chipboard as it was put down first with the walls then going on top of it. Taking that into account I did some searching and found a guide where a tradesman cut out the chipboard and replaced it with plywood before putting new flooring down.

The explanation of what was done makes sense to me but I am unsure if I should proceed with this or get quotes to get somebody to do it for me. I have a small bedroom where I can take my time doing it in the New Year. Has anyone done this before and have any advice or comments on what I am looking to do?

Many thanks,

Dave

 

[JohnD]

It might not be all the walls, but it might be partition walls with timber studs and plasterboard skin. A small room may have only one wall where it is awkward, possibly two.

Where these walls are at right-angles to the joists, it's no prob. You just cut off the old boards flush with the wall, and screw down the new boards. Where the walls are parallel to the joists, you can screw a bearer to the side of the joist for your new board to lie on. A Multicutter is very good for cutting out the old boards against the wall. As a DIYer you can get a budget brand as long as the guarantee will last longer than the job you are doing, and it has good power and replacement blades are cheap (so not the latest Bosch). I got a Worx from Argos using a Nectar voucher which seems fine. Aldi often sometimes have a cheap one which seems OK.

For good results, unless you can slide out the old board, take off the skirtings. This will hide any slight untidiness.

I find square-edged board easier to lay (and much easier to take up) than T&G, but it is essential to nog all short joints that are not on a joist. It does not matter, at the edges of the room, if the board overhangs the joist by a couple of inches as it disappears under the skirting. Nobody will stand on it there.

I find the 8x4 sheets very heavy and awkward to carry upstairs, so measure your actual joist spacing (it might not be regular) once you have lifted the old boards, and cut them into halves, or the largest piece that you can manage, so the ends lie on the middle of joists. Some merchants will cut to order. Joist spacing is particularly likely to be changed where double joists have been used, for example under a partition or to support stairs. A circular saw with TCT blade is less tiring than a handsaw.

As you have found, chipboard is an awful material, so use WBP ply, probably 18mm if your old chipboard was. The cost will be a little higher, but the results will be better. In rooms containing water, seal it, especially the edges. You can use a diamond floor varnish, and if the fancy takes you, you can dye it with Colron first.

For rooms above unheated spaces such as a garage, add mineral wool insulation while the floor is up, stuffing it especially tightly around the edges of the room where any draughts might occur. You can also use it to reduce noise transmission slightly, but the denser mineral wool batts used by builders in cavity walls are heavier and better at absorbing noise.

Screw it down with steel Countersunk screws, leave it a couple of weeks, at least, before going round again and retightening any that have eased. Don't use a hammer as you may crack the ceiling below.

Start with that small room and you will soon know if the larger rooms are beyond you. You can do it one board at a time if you want the room to be usable between work days.

Unless your skirtings are very beautiful, just fit new rather than trying to salvage and repair the old.