Suspended ground floor with chipboard flooring

[Tony]

We have a 10yr old house with suspended ground floor of T&G chipboard. The chipboard is extremely creaky at the joints. There is no evidence of any securing to joists (no nails or screws). Quite typically for a modern house, but quite inconveniently, the flooring was fitted before the internal partition walls so it spans the whole house.

I am looking to fit a laminate flooring and before doing so need to resolve some issues in the subfloor. The subfloor moves (around 1-2mm travel) enough to cause the most horrendous creaking. The creaking is almost certainly coming from the joins between the T&G chipboard pieces.

I will be using some sort of softboard underlay for the laminate, which should even out any irregularties satisfactorily. However, I am concerned that the creaking will still be apparent.

I am keen to resolve the movement in the subfloor as much as possible before laying the laminate. Everyone recommends talc, but it is a short-term fix and ineffective in my experience anyway. I would quite readily start screwing the floor down but there is no evidence of existing fixing to joists - how is this floor stuck to the joists?? I have no idea where the joists are. I drilled a small hole through the floor and encountered polystyrene-like insulation... there could be pipes and wires anywhere so I'm reluctant to explore too much further. I can't easily take the floor up because its T&G and goes under the partition walls...

I previously laid ceramic tiles to the kitchen floor (also suspended chipboard) and resolved the movement problem by laying exterior-ply (18mm) screwed at 20mm centres. Because of this, movement is not noticable in the kitchen floor.

My questions are these:

1) will softboard be enough under a laminate? I not only want to reduce movement but especially the creaking. 2) if not, I have considered laying ply to try to act as a stabiliser. I wonder if 9 or 12mm ply would do? (its expensive stuff!) in view of the expense of ply, could I use OSB instead? 11mm OSB is only =A33.34/m2 vs =A38/m2 for ply. 4) i have read that screwing through the join in T&G boards could stably connect two boards and reduce or eliminate friction noise in travel. I did a very small experiment but couldn't really assess the success because I'd need to screw all the way along a join. Anyone got any experience of this?

Any help on these questions, or any other advice/feedback would be most gratefully received.

Cheers

[meow2222]

2cm??

Bend a sheet of each and see. 9mm ply is pretty floppy, so no. I dont know re 12mm.

Whatever you use, if you glue it to the chip the 2 layers will make a much stiffer result than 2 unconnected layers. Chip is affected by water tho...

no, but I cant believe it for a moment. Work out the forces on the joints, chip is pretty weak stuff, especially when just 18mm/3 =3D 6mm thick.

18mm chip would be much cheaper than ply. Glue it down and you've got a good stiff structure. If access is ever needed its done by drilling/ cutting a very large hole.

NT

[Dave Plowman (News)]

Ah. Are you absolutely sure it is a suspended type with joists? Some are just chipboard laid on polystyrene on top of concrete. That would account for the lack of fixings showing.

[gazz]

I'll second that, 99% of mas produced houses built within the last 15 years, the ground floors consist of compacted earth, plastic sheet, slabs of polystyrene and chipboard,

fine when it's new, but as it ages the polystyrene compresses in the most walked areas, and you get the dipping as you walk, 2CM is easily believeable,

my parents house is built like that (henry boot home, built in '95) the hallway infront of the stairs is bad, my dad leaves his breifcase against the wall there, and anyone walking on the floor there makes it lean away from the wall due to the floor moving,

the kitchen is also a bitch, mum always wanted a tile floor, dad laid one, had to rip it up due to the tiles popping off the floor after a few weeks of walking on them,

we drilled holes along the middle of the worst dipping boards and injected expanding foam down the holes, then plugged the holes up, this cured most of the dipping, but still not enough to lay a tile floor directly on the boards.

[sm_jamieson]

messagenews: [e-mail]...

What, no concrete ? Surely that would not pass the building regs ? What with all the fuss I have had about hardcore compacting, depth of concrete slab etc. Simon.

[Tony]

thanks all for your responses. (Apols for the mistake in my post - i screwed the ply in the kitchen at 200mm centers, not 20mm).

This all makes good sense... right after I posted my questions I read something on the web about modern houses having chipboard laid straight onto polystyrene. This makes it tricky to stabilise except by overlaying sheet material. It seems to me that overlaying more chipboard flooring with offset joints and screwing to the existing might be the best option.

I'm thinking of getting huge (2.4m x 1.2m) sheets of 18mm chipboard (not T&G) to lay over the top of the existing floor and screw at 200 -

250mm centers. I'll leave expansion gaps around the edges and between sheets (don't want any more rubbing joints!). The alternative is to just get more T&G chipboard flooring and overlay, but the large sheet option is cheaper and will lead to fewer joins (T&G clipboard flooring is 2.4m x 0.6m at 18mm). The only other difference between the chipboard flooring and plain sheets is that chipboard flooring is treated for moisture resistance. We're not doing the bathroom or anything like that, so I guess I'm not so worried about this.

Sound good?

[The Natural Philosopher]

messagenews: [e-mail]...

I too feel it would probably not pass building regs. Suspect there is a slab under there somewhere.

In any case time to rip it up and sort properly.

[meow2222]

Only mod I suggest is I'd joint the sheets gluing them together at the joins, and would glue the stuff down too. It will make the whole thing a lot stronger.

Also flooring grade chip is high density, stronger and stiffer than

8x4s, plus with T&G edges it glues together well. Joints are only a problem when not glued.

NT

[Dave Plowman (News)]

Think most of these types are built on a concrete raft.

[Doctor Drivel]

Only mod I suggest is I'd joint the sheets gluing them together at the joins, and would glue the stuff down too. It will make the whole thing a lot stronger.

Also flooring grade chip is high density, stronger and stiffer than

8x4s, plus with T&G edges it glues together well. Joints are only a problem when not glued.

[Tony]

OK so I've started investigating this and I'm getting nowhere fast!

I did a trial run with some 18mm chipboard flooring overlaid and screwed at 200mm centers in a diamond pattern (I did this for my kitchen floor with 12mm exterior ply before I laid tiles.. it worked there). I did a 5 square meter section of the hallway before walking on it, and the result.... awful!! It does nothing to remove the squeak, nothing at all!

It got to the point where I started drilling small holes into the floor at regular intervals trying to find somesort of batten to screw into, but nothing! So I drilled a 7mm hole to see how deep the polystyrene goes - a good few inches before I get to concrete.

I'm at the end of my tether now. really not sure what to do to get rid of this awful squeak!

I even thought about cutting away small'ish sections of floor and inserting wooden blocks, pushing them under the chipboard to act as a support.

Any suggestions - anything at all (preferably not involving ripping the entire floor up!) gratefully received!

[Tony]

Ok, if anyone's interested, this is what I've done to alleviate the symptoms...

In the absence of any motivation to rip up the entire floor and replace I have drilled 8mm holes about 20cm apart along each of the T&G joins for the boards. I then sprayed a quantity of polyurethane foam in each hole (I could hear the foam taking up what must be a pretty large void between the floor and the polystyrene...). The foam expands quite a bit (about 300%) so I needed to be careful that I don't do damage to the floor by inserting too much foam. I let the foam cure overnight and in the morning the floor showed no deflection at all along the join I had treated.

I have consulted the polyurethane foam association and they have advise that the compression force deflection of most PU expanding foam products is about 40-50% so I can expect the foam to compress very slowly over time, with a resulting return of some of the creak. For this reason I would describe my approach as a symptom alleviation rather than a fix. However, the use of foam is a largely satisfactory approach since it maintains and improves the thermal insulation under the chipboard floor, reduces deflection and is easily applied retrospectively. If I get 5 years of reduced creaking I will be satisfied.

Before you flame me for this approach, I do appreciate its short- term'ism and its fallibility - but I needed to put pragmatism above perfectionism! (besides, my wife was getting pretty peaved at me constantly moaning about the creaks!)

[Tony]

By the way, thanks to gazz for the inspiration for the PU foam idea... I like to think of it as "botox" for chipboard floors!

[Tony]

By the way, thanks to gazz for the inspiration for the PU foam idea... I like to think of it as "botox" for chipboard floors!