Advice for floating engineered oak floor please

[Triggaaar]

I'm hoping to put an engineered oak floor in my new guest house. The construction should be:

concrete slab (which is generally level, but a bit bumpy)
possibly a thin layer of sand or something
DPM
Celotex/Kingspan
Vapour barrier
22mm T&G chipboard
underlay
oak floor

The questions:
Is it a good idea to put something like sand down to even out the bumps in the concrete? I will chisel out any sharp stones anyway, to protect the DPM.
Is a 3mm foam like underlay good enough, since I won't need any sound insulation?
Is there much advantage in paying for a thick engineered board, as opposed to something like Howdens 14mm single plank boards? I'm quite tempted by the £20+Vat howdens price. It says it's guaranteed for 30 years, unlike their other floors (15/20). I appreciate it will not be able to be re-sanded as much as a thicker board, but does that really matter?

Any advice much appreciated
Thanks

 

[Chippyjoe]

I think you would be better off putting down a coat of floor latex,rather than sand to try and even out the floor.

Mark.

 

[Triggaaar]

Thanks Mark. I've googled that and read about a few projects (mainly garage floor). It gives the impression that latex will provide a nice seal/coat, but not fill lumps in the concrete. What are you suggesting the latex will do (or have I got the wrong impression, and you can put it down thick)?

 

[alex s]

Thanks Mark. I've googled that and read about a few projects (mainly garage floor). It gives the impression that latex will provide a nice seal/coat, but not fill lumps in the concrete. What are you suggesting the latex will do (or have I got the wrong impression, and you can put it down thick)?

Building Control will generally prefer a layer of sand between the concrete and the DPM anyway.

Also if you are near a Tops tiles they do a price match plus 10% more off. So always worth a go.

This is the stuff I use for underlay http://www.screwfix.com/prods/52649/Flo ... y-with-DPM

Lays well and is stong and a lot less likley to tear move than the white foam type.

If budget is tight I would suggest this..

http://www.screwfix.com/prods/46572/Flo ... AY-_-46572

 

[WellsWood]

OK here's what my in house expert says:

1. 2 part liquid DPM ont the concrete, we would probably use something like Uzin PE360, a 2 part water based formula (this isn't available to the public but it's something for you look up an equivalent) if you've got any particular high points grind them out first.

2. level with a water based self-levelling smoothing compound - these are numerous and available all over Wickes etc. If you can get it Uzin 152/150 is the one to go for, but again probably hard to geet retail. Be aware that the termed "self-levelling" is something of a misnomer - it will self smooth so you'll get a pretty flat surface (certainly flat enough for a floated timber floor) but it won't necessarily be like water in a glass.

3. Tuplex underlay by Kahrs next, this is about 5mm thick and has a built in vapour barrier, chances are you won't need the celotex at all since this has pretty good insulation properties inherant (I've got something very similar in my workshop roof and it's supposedly equivalent to 2" of polystyrene).

4. Wood - Kahrs is recommended, it's worth the money. 14mm engineered boards floated with appropriate expansion gap all round.

5. Job done! - take your shoes and socks off and enjoy your new floor.

My "in house expert" BTW is the senior estimator for the largest commercial flooring contractor in the UK (and she's knows her stuff).

 

[Triggaaar]

Building Control will generally prefer a layer of sand between the concrete and the DPM anyway.

Building control aren't interested in coming back until the job is finished. How thick a layer of sand would you suggest, and what type of sand?

Thanks

 

[Triggaaar]

Thanks Mark

2 part liquid DPM ont the concrete - something like Uzin PE360, a 2 part water based formula (this isn't available to the public but it's something for you look up an equivalent)

I'll see what I can find. If anyone can recommend an equivellant, great.

level with a water based self-levelling smoothing compound

good idea, although more self-smoothing than levelling, would help with the odd holes etc

Tuplex underlay by Kahrs next, this is about 5mm thick and has a built in vapour barrier, chances are you won't need the celotex at all since this has pretty good insulation properties inherant (I've got something very similar in my workshop roof and it's supposedly equivalent to 2" of polystyrene).

I'm a bit sceptical about these things that are a few mm thick and supposed to be good insulators. Never really up to it in reality IMO. I have 70mm of kingspan already anyway, but thanks.

4. Wood - Kahrs is recommended, it's worth the money.

When I searched these forums I found that quite a few people have recommended Kahrs, but it's a bit expensive. If the room I was doing was in the main home I'd be able to justify it, but as it's in the guest house/play room, I really need to spend less.

So you (/you're in house expert) wouldn't bother with a chipboard floor under the oak, but I assume that's because you'd sort the concrete base, and leave out the kingspan, which isn't really an option for me.

Thanks for the advice

 

[Dave S]

I laid a floating oak floor last year - wouldn't do it again.

Unless the floor is like a billiard table the underlay will be unable to take up the imperfections - result, the floor creaks whenever you walk across it. I even took it up and screeded the concrete but it didn't improve that much.

I found the thicker fibre type underlay to be far better than the thin foam type.

If I lay another floor it will be battened or else stuck down - there are some threads about suitable adhesives on this forum if you do a search.

cheers
Dave

 

[WellsWood]

So you (/you're in house expert) wouldn't bother with a chipboard floor under the oak, but I assume that's because you'd sort the concrete base, and leave out the kingspan, which isn't really an option for me.

Thanks for the advice

Exactly, but it doesn't really make any difference. If the subfloor isn't flat to within the required tolerance (within 3mm per metre from memory) then the chipboard won't be either because it will take on the shape of whatever's under it eventually. Any dips or hollows and the floor will bounce as it receives traffic which will do the joints no good at all. Unless you're nailing it down to battens/joists (and engineered boards aren't designed for this) then you're pretty much stuck with having to get the subfloor within tolerance. You're right about the price, it's not cheap at around £40/m2 retail, which is why it's important to get the prep right.

 

[Triggaaar]

I laid a floating oak floor last year - wouldn't do it again.

Oh great

I found the thicker fibre type underlay to be far better than the thin foam type.

Maybe that's what I should go for then, although I think the chip flooring will be pretty smooth.

there are some threads about suitable adhesives on this forum if you do a search.

I thought they were more for solid oak floors rather than engineered (I've had trouble with solid oak floors before, so I want to avoid that), but I'll have another search to see what I find.

If the subfloor isn't flat to within the required tolerance (within 3mm per metre from memory) then the chipboard won't be either because it will take on the shape of whatever's under it eventually.

I don't think my concrete is that bad, I levelled it with a piece of 6x1, but as it was going off and as I couldn't walk on it, it ended up with a few bumps. In the bumpy areas the bumps go up and down repetitively every inch - I will try and address that, but even so, I think the peaks and troughs are too close together for the kingspan and chipboard to bend (the chipboard could span 400mm floor joists).

you're pretty much stuck with having to get the subfloor within tolerance. You're right about the price, it's not cheap at around £40/m2 retail, which is why it's important to get the prep right.

Yes I agree, definitely worth getting the prep right, or you have to pull the lot up and do it again, which costs a fortune. I want to learn about some of these levelling compounds, it'd also be nice to get a good finish on my shed (which is attached to the guest house). There seems to be a lot to choose from with quite different purposes.

 

[xy mosian]

Won't the Kingspan nicely take up any small problems with a rough surface?
Of course this may destroy some of the insulation properties.

xy

 

[WellsWood]

don't think my concrete is that bad, I levelled it with a piece of 6x1, but as it was going off and as I couldn't walk on it, it ended up with a few bumps. In the bumpy areas the bumps go up and down repetitively every inch - I will try and address that, but even so, I think the peaks and troughs are too close together for the kingspan and chipboard to bend (the chipboard could span 400mm floor joists).

Ah, my mistake, I thought the issue was the concrete being out of true to a greater extent. You're right then, the Kingspan should comfortably absorb the ripples.
In which case why not go for a good laminate instead of the engineered board - since a good laminate is a better option than a cheap engineered board - and will save you around £25/m2.

 

[wizer]

Good, I'm glad you're an expert on this subject Mark....

 

[WellsWood]

Good, I'm glad you're an expert on this subject Mark....

Well I don't know about that, but I certainly know someone who is :wink:

 

[Triggaaar]

In which case why not go for a good laminate instead of the engineered board - since a good laminate is a better option than a cheap engineered board - and will save you around £25/m2.

The engineered board from Howdens is only £23/m2 - I assume a decent laminate is about half that, so saving me about £400 total.

But what is better about a good laminate than a cheap engineered board? Obviously if the engineered board is so bad it fails, that speaks for itself, but I'd hope the Howdens board would do the job. If not, then I guess I need to look at more expensive or just go laminate.

 

[WellsWood]

But what is better about a good laminate than a cheap engineered board?

Basically because it's always better to buy the best product you can afford, so purchasing at the top end of one product type is likely to get better results than purchasing at the bottom of another. Just because engineered boards are generally more expensive than laminates doesn't automatically make them better, just different products with different raw material and manufacturing costs. If the market leader charges £40/m and a competitor can do a similar product for £25 the first thing you need to ask yourself is where the difference has been saved.
But at the end of the day it's not going in your living room (not that that really makes a difference), so just pick something you like within your budget. As long as it's laid according to manufacturers spec. pretty much everything will do what it says on the tin and be suitable for it's intended use. Your only issue then is whether that intended use matches your requirements.

 

[Triggaaar]

If the market leader charges £40/m and a competitor can do a similar product for £25 the first thing you need to ask yourself is where the difference has been saved.

Indeed. Thicker oak on the top, a bit more product, and higher profit margin I assume.

But at the end of the day it's not going in your living room (not that that really makes a difference), so just pick something you like within your budget. As long as it's laid according to manufacturers spec. pretty much everything will do what it says on the tin and be suitable for it's intended use.

Not being in our house means it'll get less wear. If the cheaper one does the job, I'll be happy.