Chipboard Floor

[securespark]

I plan to lay a new 22mm chip floor.

I shall put 100mm Kingspan or similar under the floor first.

Is it:

1. Better to use ply?

2. If using chip, would you PVA the tongue and groove?

3. Would you bead flexible adhesive on the joist-tops to minimise squeaks?

4. Would you foil tape over the joists to give continuity to the vapour barrier?

5. Or would you lay a sheet vapour barrier under the chip?

Thanks for your suggestions.

 

[endecotp]

The other option is 18mm T&G OSB3, which you might consider “half way” between chipboard and ply.
I’m using it over insulation boards but fully floating, with no joists, so I can’t comment on your questions.

 

[foxhole]

I plan to lay a new 22mm chip floor.

I shall put 100mm Kingspan or similar under the floor first.

Is it:

1. Better to use ply?

2. If using chip, would you PVA the tongue and groove?

3. Would you bead flexible adhesive on the joist-tops to minimise squeaks?

4. Would you foil tape over the joists to give continuity to the vapour barrier?

5. Or would you lay a sheet vapour barrier under the chip?

Thanks for your suggestions.

Where is this floor?

 

[securespark]

Over a f-f-f-f-f-f-freezing unheated garage.

When you sit on the loo in the night (as blokes my age are wont to) you can feel the wind whistling under the skirting....

 

[securespark]

(The men in this house sit down to pee then there's no complaints from Mrs Secure!)

 

[foxhole]

So 1st floor? What’s the depth of the joists?

 

[JohnD]

I'm sure we've had this conversation seven or eight times before

Mineral wool is better for blocking draughts, because you can stuff it between the joists and it will pack tightly. Especially around the edges of the room where draughts and dirt blow up under the skirting.

Foam board has to be cut with precision, and you will still end up foaming the gaps.

And

I prefer ply because I have found chipboard very shoddy.

I don't think glue is enough. I like joists or struts under all joints in the board. If you screw it down you have the possibility to lift it in future without using a chainsaw.

 

[securespark]

So 1st floor? What’s the depth of the joists?

A ton 70.

I'm sure we've had this conversation seven or eight times before

And I thank you for your extreme patience and help. TBF, I cannot find the threads.

Mineral wool is better for blocking draughts, because you can stuff it between the joists and it will pack tightly.

I thought a gap of min 50mm had to be left on the cold side?
Plus, rigid has a superior value.

I prefer ply because I have found chipboard very shoddy.

But then you need to add support for all edges.

I will be screwing as well as gluing.

 

[JohnD]

heat losses from a floor are mostly to do with the cold air blowing around. There is no convection of heat escaping downwards, and with a 20C difference, negligible radiation. i don't think that the thinner foam layer will make a noticeable difference to those aspects. But for air currents, mineral wool is really good, and you can pack it in to stop the cold air blowing around.

I don't recall a need for a gap, like under a loft floor. Unlike lofts, you won't get water vapour travelling into the void, because it is lighter than air so it rises. I don't see that it will condense on the underside of the floor, because the floor is part of the room so will be warmer than the subfloor void. You will probably end up with a bit of a gap, because the joists might be 7-inch or so, but with the edges of the room well packed, there's no draught.

It also muffles noise a bit, if that matters.

 

[Deleted member 174758]

Unlike John, who has presumably got a stash of incredibly high quality plywood from the 1990s BC (before China) my experience of dealing with the vast majority of plywood that builders merchants and sheet stock wholesalers sell these days is that it is extremely variable in quality - although most is Chinese and is just plain carp unless you are fortunate enough to get Malaysian or Brazillian (difficult, and you will pay a premium for it). If buying chip t & g chip I'd recommend Egger or Kronospan and I'd suggest going for the P5 (moisture resistant) grade. All joints should be glued with a D4 (waterproof, non-expanding/foaming) glue and ideally the boards should be glued to the joists as well. The glue always goes into the groove, and don't be stingy with it. Do that, make sure that you close up the joists properly (my tools for that are a piece of 4 x 2 softwood and a sledgehammer - so you need to start with the tongue edge facing the wall) and screw to the joists at 150mm centres and there is no need to put down flexible adhesive, which in any case won't stop squeaks.

To be fair cheap chipboard can be awful stuff, but I find the biggest issues with chipboard flooring are down to poor installation, often as a result of fly by night price work practices, e.g insufficient/wrong glue used, boards nailed as opposed to screwed, insufficient fixings, board joints not pulled up tight when installed, board joints not supported on joists (or noggins) and inadequate size joists. Still, it gives me one or sometimes a couple of lucrative jobs every year sorting out shoddy installation. But I still don't use ply most of the time

 

[securespark]

Thanks fellas.

It would certainly be less of a ball ache to use MW.

I always thought you had to leave a gap for ventilation under the insulation because cold air coming in from the unheated room below will potentially meet warm air in the bedroom above?

I know a bit about electrics, but not much else!!

 

[JohnD]

Cold air will contain less water vapour than warm air.

Relative Humidity, innit.

 

[securespark]

As Toyah sang, "It's a mystery, oh it's a mystery......"

Thanks for explaining it.

So I can stuff all the under-floor spaces to the gills with insulation without worrying about condensation?


Can I use the stuff made out of recycled plastic bottles? Trying to be a bit eco.

Edit:

I bought a roll of plastic bottle stuff to evaluate and it's great to handle.

What thickness would you go for?

Do cold pipes passing through the under-floor space need lagging?

 

[Deleted member 174758]

Can I use the stuff made out of recycled plastic bottles? Trying to be a bit eco.

Which is another reason for using chipboard over plywood: the vast majority of structural plywood available from the big DIY outlets and smaller merchants is hardwood plywood and comes from (in the main) virgin tropical forest. Even OSB comes from a mixture of first growth and managed sources (albeit softwood, so a potentially renewable resource). Chipboard, on the other hand uses a larger percentage of the original (almost exclusively softwood) tree than other sheet materials and mist modern chipboard contains a percentage of recycled chipboard as well (Egger process their own bought in chipboard scrap up in the north east). Chipboard is also made here (so smaller transport carbon footprint) unlike plywood which is all imported these days

 

[JohnD]

Can I use the stuff made out of recycled plastic bottles?

the white plastic stuff is OK to handle, but I prefer the mineral wool treated with Ecose, which prevents it shedding irritant dust and fibres.

Unlike the foam slabs (and presumably the knitted bottles) it is not flammable and does not emit toxic fumes in a fire. I got more cautious after Grenfell.

Because there is no convection loss, I expect 100mm will do, except round the edges of the room, which you need to stuff. If you can block the draughts, that will make the biggest difference.

I think I used 150mm which is a fair fit with 7" joists.