Fixing timber pieces to standard new mdf floor

[Sadruddin]

I have a number of salvaged pieces of tongue and grooved floor, mainly around 30cm in length, which I am planning to reconstitute into a floor.

I'm planning to cut them all, either to the same lengths, or not, and basically lay a tongue and groove patchwork, glued at the cut ends, and in a running bond for strength. The floor will then be sanded.

It will be the floor for a first floor bathroom, just over two metres by about three.

2 questions, well, maybe three, I'll do the maybe one first.

1) Is this just a really stupid idea, and if so, why?

2) If not, am I best gluing the pieces directly to the mdf floor before sanding, which will take quite a lot of glue, and would wood glue be sufficient, or would tongue and groove screws be better?

3) I am thinking of sanding using an upright sander and then sealing the whole floor before putting bath and toilet in. Would just a good quality, say, polyurethane seal be sufficient?

Thank you in advance

 

[Deleted member 174758]

Are you sure the floor is MDF? It's not really suitable as flooring, especially in bathrooms - we tend to use either plywood, chipboard or OSB as sub flooring

 

[foxhole]

Not a great idea in a bathroom and agree with J&K observations.

 

[Sadruddin]

At the moment we just have the usual chipboard P5 flooring. If covering that in OSB is the next step, then OK.
And over that, what should we do with the timber, please?

 

[Deleted member 174758]

Right. So you have P5 chipboard sub flooring and not MDF. They are radically different materials and I was concerned that if it were true, you'd need to replace the entire sub floor! As it is, P5 is a good sub floor and you won't need to cover it with OSB or anything else.

What you will need to do, though, is fix the softwood down onto the P5 chipboard in some way. Assuming it is 22 to 25mm thick, and that your P5 is 18mm I'd actually nail or pin (16 ga) it down through the grooves and into the chipboard ensuring that the nails or pins don't pierce the bottom of the chipboard (because of the risk of hitting wiring or plumbing beneath the floor). I'd recommend that before you nsil or pin the flooring pieces you seal the undersides of them with the same stuff you intend to use on top to finish them. I'd also suggest using a D4 flooring adhesive to glue the timber pieces together (applied into the grooves) after they've first been pinned or nailed in place. An alternative to pinning or nailing might be to treatvthem like pieces of parquet and use a parquet adhesive such as Lecol 5500 to hold all the pieces in place. That would negate the need to pin or nail

After initial sanding all gaps will need to be properly filled (using a filler such as Lecol 7500 which is mixed with sanding dust from the actual floor to form a stopping paste) before finish sanding and then sealing with a waterproof lacquer

 

[Sadruddin]

Thanks. That covers exactly what I needed to know. Brilliant! Just the help I needed.

 

[JeannetteWade1144]

When using Lecol 7500, what should the ratio of sawdust/filler be, roughly? Thanks

 

[Deleted member 174758]

You mix enough to get a soft paste, slightly softer than toothpaste. In fact this video gives you a good idea of how it should be done (although as he says he did get it slightly too runny):

You really do need a big floor scraper like the one he's using - and I suggest that you round the corners of the blade off before you use it (with an oilstone, on the back step if you have one, on a paving slab, etc) as they always come with sharp corners which can dig in and mark the floor. For smaller holes and defects a plastic spatula or a very flexible metal stopping knife (again with the corners rounded off) is the tool to use. 7500 dries in 30 to 60 minutes, so you need to work quickly - if needs be do the floor in 2 or 3 sessions - and it's a solvent filler so it is a bit pongy. The room does need to be warm to start with, though, 15 to 20°C