MDF floorboards

[yesmaybe]

Hello,

I have just had some floorboards up in a bedroom, to inspect the pipes there under and the original timber floorboards are in bad shape. The person below was also complaining of squeaking boards; the original floorboard nails have been in and out a dozen times I would guess, and some non standard 2" nails used in places. The existing boards have areas of dry rot or wood worm and so split when the chisel kissed it. So patches need replacing. The joists are sound.

The existing boards are 3/4" thick and 6" wide. I would be replacing three or four joists width (12" spacing, joist 2-3" width) so the longest strip would be ~150cm (60"). They would fit snugly under the skirting at one end.

I have read on here to NOT use MDF, but some of that advice was going back ten years. For reasons including: it would null your insurance; not load bearing; it would warp over time; screws will move and squeak; water damage, etc.

Well, I have just been given from a skip some MDF off cuts which are 22mm thick (ideal), 15cm wide (perfect) as well as some which are 40cms and 6cms (perfect as a triple). I couldn't believe my luck.

Based on those measurements, bearing in mind it will be a low traffic floor (bedroom) and be partially covered by the wardrobe, do you think the MDF would be strong enough? Fixed down with no4 55mm screws.

The existing underlay and woven carpet will go back down.

Please say it's fine as I've started already... But now reading on here and I'm beginning to worry.

 

[vinn]

Forget the MDF for use as a flooring - dont use it.
Are you actually talking about MDF or chipboard?
If you are replacing floor board lengths here and there then use similar floor boards as replacements.
Are these boards T&G or square edge?
Use screws not nails - screws give a firmer fixing and a second chance.

It would help if you posted photos?

 

[yesmaybe]

Is that a stock answer or did you just gloss over my post?

I am specifically asking about MDF; if you say no, please explain why, what are the risks?

I am using screws, not nails.

These are old timber straight cut boards, not T&G.

I will try and add a photo when back on site tomorrow.

A thanks for your fast reply, so far. Do you want to see the MDF or the rotten planks?

 

[Burnerman]

MDF is truly a ghastly material....as it is made from compressed dust it has little strength in any plane. It doesn't like wet but it doesn't warp......as for nulling insurance, I've never heard of that one!
It isn't recommended in any traffic area, however (sticking the neck out here) if its really well supported you could get away with it! I'd certainly use something else though, such as original pine boards or ply.
John

 

[JohnD]

from a skip some MDF

Best place for it.

Save up for some ply.

 

[big-all]

as said dosnt like damp off any sort

any point loading like a bed leg will likely sag keep in mind its thick cardboard

 

[yesmaybe]

Thanks John, well we certainly don't want any necks stuck out, or worse. It seems perfectly firm enough in place. I have even bounced on it, to prove to myself the squeaks have gone. However, if it isn't going to be safe for the next two-three years, then I best go down to Jewson's. Or I did see an advert for a reclamation warehouse recently, perhaps they will have some old cheaper replacement floorboards in the correct widths..

 

[Burnerman]

If it's good now, there's no need for it to change in time. Please understand, it's not really good for us to recommend materials that aren't really suitable.....some folks would use this stuff over long, unsupported spans - with bouncy results!
John

 

[big-all]

.....as for nulling insurance, I've never heard of that one!

maybe unsutable material for purpose ??

 

[yesmaybe]

Right, now I'm in a dilemma, in a way I wish I never asked, but I do want it to be safe (if not a 'proper' job). It seems there may be an anti-mdf brigade .. I am sure real wood is better, but what about the recycle aspect of it... I have never used the stuff before, but on appearance it seemed a strong versatile material (at the least it was heavy carrying it up to the bedroom). Perhaps there is different quality stuff, the sellers blurb makes it seem so. Perhaps I will test it with the bed leg on it and a couple of bounces and see what the anti-milf brigade say about that... I could consider laying 6mm ply on top of the whole lot, but that's a job I don't want to do for no reason, guaranteed that will bring further snags to an already delayed inspection.

"MDF 2440mm x 1220mm x 22mm MDF -Medium Density Fibreboard is an extremely versatile product. This product is widely used throughout the building and furniture industries. MDF also lends itself to many D.I.Y projects across the globe. It gives you the benefits of using a timber product without the natural defects."

 

[Burnerman]

Aye, difficult and maybe a can of worms here....MDF isn't a structural product in any form and would never be used solely for flooring. However, in your situation it seems to be working fine and no disaster is likely to result from its use and it won't deteriorate with time.
I've seen floors with large MDF patches, and no problems.....even the carpet adds added strength - it just doesn't seem kosher.
I can't comment on any insurance issue, and can't see any situation where it would apply in your case.
John

 

[big-all]

ok lets try a different tack
wood gets its strength from the fibers along the plank giving strength like a handful off 3m copper tubes fixed together side by side
you now chop the copper pipes into 50mm lengths squash and glue together completely random directions you now have about 4 times the material with far less strength
you have been advised by experts
now do a search on line for structural mdf flooring and then think why you have a page with no links

 

[iwilson16]

Check out some of my old posts and photos. I've used 25mm plywood to repair chunks of broken floorboards. What i did was work out all the lengths and widths required, then went to a timber merchant, bought 1 sheet of 2400x1200x25 plywood and ask them to cut it up to my requirements and deliver it. They will charge a little for the cutting and delivery, but it's worth it.

One reason I chose plywood that's not been mentioned here is that it's easy to get a screw close to its edge, which is very useful when you might have to fix to just half a joist width at the edge of the patch. I wouldn't trust screwing closer than 20-30 MM. to the edge of mdf.

Ian

 

[Gerrydelasel]

It seems there may be an anti-mdf brigade

No, MDF is indeed very versatile, but as floorboards it is not appropriate. If it gets damp it will disintegrate; a wide board (you say yours are 6" which is quite wide) will bow under the pressure of a bed leg (I have a 30mm MDF table tope that was leaning against a wall and it bowed under its own weight within a few weeks!) and as it does so it will easily pull away from any nails or screws because it is so fibrous. It's simply not physically strong or robust enough for floorboards, unless you want to patch (bodge) a really tiny area.

 

[Diver Fred]

I can only agree with what others have said - Don't use MDF!!!

But I also think you have other problems; you mention dry rot and/or woodworm, that needs resolving before the boards are replaced, even if can only see it in the boards you have taken up you must still treat any timber in the area and treat the new timber before you fix it in place including the ends/edges.

Finally using screws to fix the new boarding down - good idea but again care is needed in the choice of screws; to stop squeaks I strongly recommend that you use screws with 'Shanks' (i.e. not threaded for the full length of the screw) otherwise you will never be able to ensure the new boards are tight against the joist. BTW - I think you are mistaken about screw sizing getting imperial and metric measurements crossed - No4 is about 2.5mm dia and the longest I've seen was 1 inch long; think you mean 4mm dia by 55mm long.

W