Really basic flooring questions

[John Rumm]

Yup, that will often do the job, and in this case would save spoiling the view from below. Although it makes it harder to avoid a step into the room.

[The Natural Philosopher]

And oak is not that much higher in elastic modulus than any other wood

I'd say this is a definite case for building a false floor 4" above the current one and bracing it.

[newshound]

It may just be one or two joists not doing much because of beetles at the ends (or where they rest on sleeper walls). Provided the tops are levelled up as someone suggested and then decent sheet material is screwed firmly to the joists to make the whole thing into a single structure this may be sufficient. I have a top floor a bit like this. The wide elm boards are quite wormy too and I am currently not bothered about the movement.

I rejected an 18th Century house because I was worried about this about

35 years ago (following experience with dry rot in a Victorian one). After 30 years in this one, with almost as much floor movement, I now realise that 4x3 oak joists and 12x1 elm boards degrade much more slowly than pine.

[Roger Hayter]

An interesting idea. But (apart from having to do all the plumbing and wiring that runs along the bottom of the walls) there is nothing to support such a floor except the existing floor, and the purlin is only

6' 10" above the existing floor. I was actually thinking of laying some sort of rubber soundproofing on the exisiting floor and boarding over it, but there is not much room for effective bracing.

[Roger Hayter]

A step into the room is acceptable, if some sort of double layer floor would improve things. Sound proofing is also a significant objective.

[Tricky Dicky]

With 6'10" between floor and purlin it does not give you much scope to raise the floor level. What is the scope the other way of lowering the ceiling in the room below?

If you do have height available it might be creating a bigger job but it if you removed the oak beams and put in decent depth joists you could reattach your oak beams merely as a decorative feature.

Richard

[Roger Hayter]

Intriguing idea, but the ceiling below is 6' 4"!

[Tim Lamb]

If you are confident you will never need to lift this floor again, I would secure everything with polyurethane resin as well as appropriate wood screws. We have an extension floored with carpeted 18mm chipboard nailed to pine joists. Even a child moving about leads to *creaks* heard in the kitchen below. I would use glue but for access to wiring and plumbing:-(

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[Tricky Dicky]

Your f******d then, all you can do is replace the flooring with boards if that is the look you want from below and put up with the movement and slope. What is it you are living in? It seems to be a very old cottage built in times when people were an awful lot shorter.

Richard

[Tricky Dicky]

Just another thought but the solutions are getting more expensive. Have you considered inserting two more beams in the room below that would reduce the span between supports for the oak joists to about 1.25m thus reducing the flexing it would give you the opportunity to jack up any joists that are sloping downwards. Getting suitable oak beams is not going to come cheap even if you can get hold of old beams from a demolished cotton/wool mill which were often made of oak. RSJs clad with oak panels might be another solution but may not give you that "olde worldy" look if that is what you are trying for?

Richard

[Andrew]

If he uses 22mm 8*2 T&G caberflooring and glues the joints it will be rock solid.

Helps to use a power planer on the tops of the joist to get them more or less at the same floor height.

[tabbypurr]

A new floor 4" higher up? C'mon, really. Just lay the ply.

NT

[tabbypurr]

rubber rocks maybe

That would help the floor to bend about even more. Wonky 4x3s is not a structure that would suit ceramic tiles. Vinyl or carpet tiles no problem. For ceramic tiling to last you really do need it rock solid. Tiles onto 22mm sheet will work for a while, but not long term.

NT

[John Rumm]

In which case you could redo the current floor in whatever state of level it is now, then using firing strips to level, and flooring sheets on the top. You could stuff the gap between floors with rockwool etc to get a little bit of extra sound proofing. (sealing any air gaps also helps)

[The Natural Philosopher]

put it underneatth new floor

So?

I dont know how deep your existing joists are - the 4" or the 3" but the center span deflection goes up as the depth, so doubling it is 1/2 of the deflection, and adding a stressed ply skin takes it down even further.

Screwing a stressed ply to the existing then adding more beams then more ply to create a rigid box would be even better.

Think how rigid a cheap hardboard and softwood door is.

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[The Natural Philosopher]

Then extend my previous idea - two skins of ply on as thick a skeleton as you can accomodate, filled with dry sand.

[The Natural Philosopher]

+1.

[John Rumm]

Can't say I have had much difficulty in the past.

Some will certainly - things like SF Turbogold are not that good into oak without a pilot - but there are others that are fine IME.

(in fact some slightly softer woods like Sapele can be worse)

Perhaps you were doing it wrong?

It works for me:

[John Rumm]

If you are keeping the exiting floor[1], then scribe in firing strips running counter to the existing joists. Don't feather them to nothing, but leave as much minimum height as you think you can spare. Fix them to the floor, add sound absorbing materials in the gaps, and then screw the new floor too them. That will do a reasonable job of spreading any load out over several original joists at a time.

[1] Although still replace any existing boards that are actually rotten!

[Alex James]

Why is glue so terrible.

If you want to take the chipboard up you are likely going to destroy it. I wouldn't have thought using a multi tool to separate the glue was that much more work.

Am I missing something?