Need of Help! Chipboard Flooring + PIR + Taping Headache

[mattwaddy]

So I'm about to order a routed chipboard structural flooring from Omnie (22mm) which will replace my current floor boards. The joists on this suspended timber floor (downstairs) are 100mm deep and so I've purchased some PIR insulation and was planning on taping all joins and over the joists so it creates a continuous vapour layer. Including against the walls. My dilemna is that chipboard flooring is usually glued down, and I'm now worried that if I span 100mm foil tape over the joists joining the two PIR boards either side it won't leave a suitable surface i.e. wood for the glue to adhere to. I was going to glue the tongue and grooves and also every joist and noggin supporting the floor, then screw it down.

Which of the following should I do

1.) Tape it all with foil tape as planned and simply glue the boarding down to that
2.) Tape only the joins where PIR meets PIR but not against or over the joists leaving a glue area but slight air tightness issue
3.) Something else?

I'd love to get a comfortable answer for this before I place an order for the UFH chipboard flooring today. I've already got the PIR and tape arriving on Friday

 

[jeds]

I assume you are planning to put the PIR between the joists? My advice would be glue the joints but not the joists - leave the board as a floating floor. You could then lay a poly sheet over the whole thing as a vapour layer.

 

[Deluks]

You don't really need to tape the joints over the joists, and you don't need to glue the floor to the joists either, imagine having to lift it up in the future, nightmare!

You can achieve airtightness by cutting the insulation accurately and by using a foam gun to seal any gaps.
The chipboard should be screwed down, the glue is supposed to be used in the tongue and groove joints only.
Top tip: T&G plywood is a superior product to chipboard flooring, but does cost a little bit extra. (Stronger, more resistant to moisture)

 

[mattwaddy]

I assume you are planning to put the PIR between the joists? My advice would be glue the joints but not the joists - leave the board as a floating floor. You could then lay a poly sheet over the whole thing as a vapour layer.

Yep between the joists with the PIR in firm and on small brackets for support. This is a UFH routed structural board, and the manufacturer guidelines state to glue to the joists and T&Gs, with it being a UFH not sure a VCL over the top would be a good idea

 

[mattwaddy]

You don't really need to tape the joints over the joists, and you don't need to glue the floor to the joists either, imagine having to lift it up in the future, nightmare!

You can achieve airtightness by cutting the insulation accurately and by using a foam gun to seal any gaps.
The chipboard should be screwed down, the glue is supposed to be used in the tongue and groove joints only.
Top tip: T&G plywood is a superior product to chipboard flooring, but does cost a little bit extra. (Stronger, more resistant to moisture)

This is a UFH routed structural board made of chipboard so no option for ply, although it does have a 6mm ply over it once fitted to protect the pipes and for the finished floor to sit onto, and the manufacturer guidelines state to glue to the joists and T&Gs, there are no services under the floor they've all been moved to the first floor so just the air vents and circulation under it and hopefully never need to access it.

 

[Deluks]

Just had a quick look at those omnie boards, they have an aluminium foil layer built in. I wouldn't both with taping, just seal the gaps.

 

[freddiemercurystwin]

You don't glue boards down to the joists, it would soon fail anyway as the joist will expand/contract differently to the boards anyway, screws allow for a little movement.

 

[mattwaddy]

Just had a quick look at those omnie boards, they have an aluminium foil layer built in. I wouldn't both with taping, just seal the gaps.

Yeah the TorFloor 2 has a routed chipboard layer and the foil diffuser is built into the ply layer. So perhaps just go with filling any gaps with expanding foam and maybe taping the joins where PIR meets each other, then leave the timber joists so they can be glued. I can see the topic of glue no glue is a 50/50 thing. But I'll likely need to follow their advised process

 

[mattwaddy]

You don't glue boards down to the joists, it would soon fail anyway as the joist will expand/contract differently to the boards anyway, screws allow for a little movement.

I've been reading some threads on this forum and it seems it's a split subject, I'm just trying to follow the manufacturer guidelines in this instance as it's a wet UFH system

 

[jeds]

I've been reading some threads on this forum and it seems it's a split subject, I'm just trying to follow the manufacturer guidelines in this instance as it's a wet UFH system

I get that matt, but these things always have to be weighed against reality. Floorboard manufacturers recommend glueing to joists but this is purely because of squeaking floors. In the past boards were never glued and squeaking was often an issue. The easiest way to avoid this is to glue boards to joists and so it entered the standard recommendation. If you choose not to then that's your problem. I would say that Omnie (and I am very familiar with Omnie grooved systems) have put this in their recommendation on the back of the board manufacturer's - no other reason.

But glueing still remains optional and many do or don't depending on the situation. Ask yourself; what is the risk? What could go wrong if you don't glue? A: nothing! providing you design correctly and avoid joint movement. (by glueing joints)

 

[mattwaddy]

I get that matt, but these things always have to be weighed against reality. Floorboard manufacturers recommend glueing to joists but this is purely because of squeaking floors. In the past boards were never glued and squeaking was often an issue. The easiest way to avoid this is to glue boards to joists and so it entered the standard recommendation. If you choose not to then that's your problem. I would say that Omnie (and I am very familiar with Omnie grooved systems) have put this in their recommendation on the back of the board manufacturer's - no other reason.

But glueing still remains optional and many do or don't depending on the situation. Ask yourself; what is the risk? What could go wrong if you don't glue? A: nothing! providing you design correctly and avoid joint movement. (by glueing joints)

Thanks for this. Silly question as I'm not an experienced diy person, but trying tl be more so. If I glue all the t&gs wouldn't i have the same issue i.e. be unable to lift the floor later? as im assuming the glue would bind the joins together and so need to be cut out somehow. I guess if people are saying to glue t&g then might as well do the joists too. But are you saying perhaps just do a fully dry install with only screws. Sorry if I sound dumb!

 

[jeds]

The joints should be well glued - add a line of glue to both the shoulder AND the tongue before bringing together. A lot of people use D4 adhesive on the joints but D4 is really for joists - the correct adhesive for joints is D3. Screwing is fine but it is imperative to use the correct flooring screws. Whatever you do don't use full thread screws, which will almost guarantee squeaking.

Of course make sure the floor structure is flat and well supported for the extra weight and that the underfloor void is well ventilated.

People do sometimes ask about taking the floor up, but the reality is that if that ever happened (why would it?) the floorboards would be trashed and you'd start again. If the void underneath is accessible, leave a hatch? If it isn't leave several smaller hatches to allow visual inspection.

PS. you will never find total agreement between manufacturer's, product suppliers, builders, guidance, British Standards, etc. All these sources commonly have slightly different versions of things, because they are always having to cover many different situations in one sentence or short paragraph. The result is they simply go belt and braces and leave the end user to apply the nuance.

 

[mattwaddy]

The joints should be well glued - add a line of glue to both the shoulder AND the tongue before bringing together. A lot of people use D4 adhesive on the joints but D4 is really for joists - the correct adhesive for joints is D3. Screwing is fine but it is imperative to use the correct flooring screws. Whatever you do don't use full thread screws, which will almost guarantee squeaking.

Of course make sure the floor structure is flat and well supported for the extra weight and that the underfloor void is well ventilated.

People do sometimes ask about taking the floor up, but the reality is that if that ever happened (why would it?) the floorboards would be trashed and you'd start again. If the void underneath is accessible, leave a hatch? If it isn't leave several smaller hatches to allow visual inspection.

PS. you will never find total agreement between manufacturer's, product suppliers, builders, guidance, British Standards, etc. All these sources commonly have slightly different versions of things, because they are always having to cover many different situations in one sentence or short paragraph. The result is they simply go belt and braces and leave the end user to apply the nuance.

I've got D3 glue ready to go, so up to me if I put it on the joists, but your recommendation is really just to do the joins between boards and screw it down with the right screws. I think Omnie supply them as part of the order, so will check what type they are before using

 

[Deluks]

Imagine having to lift up the boards in the future?
Yes they would be getting replaced, but the glued joints would stay intact whilst the board around it broke away.
You'd have strips of glued on chipboard along the top of all your joists which would have to be chiselled off before you could relay the new boards. Nightmare job.