strengthening 18mm chipboard

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Hi,

I have a large loft (55 sq meters) all 18mm flooring grade green chipboard, it is not great, it has all been glued, and screwed on 450mm joists and flat. But feels very springy.

What are my option for strengthening?

1. Covering with a solid timber 18mm? (Glued or floating)
2. 18mm engineered flooring? (Glued or floating)
3. Cover with plywood, then carpet,

For cost/speed I am inclined to go for option three, but not sure on thickness, if 18mm I need to chop doors down to get carpet underneath.

thoughts?

thanks
 
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None of those three options is likely to produce any worthwhile reduction in springiness.
The problem is likely to be more fundamental, ie the size of the supporting joists - they are probably too small.
 
Thanks for the reply.

Not convinced that is the case. Joists are 225mm (engineer specified at 600mm centres) and we even added another few so they came into 400-450mm centres) so well over spec'd.

Its the quality of flooring, had I ever seen these before (always owned older houses) I would never have specified them, and I cannot remove as walls in place.

thanks
 
Does the whole floor feel spring, or the chipboard between the joists?

If it is the whole floor then not much you can do without proper opening up works and adding more structure, gluing and screwing panels stiffens the floor but you say that has been done.

If it is the latter then another layer of flooring.
 
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Another layer may push the design limit of the floor - it isn't light.

What is the span of the joists and what were they designed to carry? Chipboard flooring is normally very stiff unless its damp and then you go through it.
 
Are the 225 joists bridged (strutted) near mid-span?
Taller joists can have a slight tendency to twist slightly when loaded, giving the impression that the decking is moving.
 
Hi,

All joists have noggins at 2m max, it was a proper brand new cut roof construction, designed to accommodate 2 x cast iron baths and 2 x bedrooms, also the rest of the house joists run the opposite way so weight should not be a problem.

Looking at it I think I will glue and staple some 6mm plywood over all of it this should stiffen it up a bit.

Thoughts?
 
Update - for the benefit of anyone searching the forum

I screwed (every 300mm) and glued (full bond) 5.5mm ply to the 18mm chipboard and it worked very well. Once the glue went off today it is a great improvement, no flex, no bounce, all in all very happy.

In the on suite I had to lay 25mm Plywood to match the height (18mm+5.5mm) and this is wonderful (if not cheap) it's like a concrete floor!
 

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