I understand the reasons for the expansion gap in a floating floor but is
10mm all round not a bit excessive? Can the floor really expand up to 20mm
in all directions?
Reason I'm asking, I'm in the process of laying a floor and have left the
10mm round the perimeter of the room (as I removed the skirting and can
easily hide the gap) but am now up against the breakfast bar and am not too
keen on a big gap and don't want to put skirting round it.
Also due to bad planning I've been left with a small (20mm) L section of
laminate to fit which only leaves a few mm expansion. There is no way I can
cut it smaller to leave the proper 10mm gap.
Lets put it this way. I laid mine in spring over a total of 12x6 meters
with a large cutout for a central chimney and hall. So a sort of U
I left about 4-6mm in most places but some was cut tight to the wall in
Come summer, it was lifting all over the place.. I had to relieve it by
4-6mm at one place.
The expansion was mainly across the grain of the boards - these were
Kahrs interlocking oak laminate engineering boards.
I would say total movement along the boards - across the 6m depth of the
tow combined rooms and passage - was about 4mm total.
It was more like 10mm or more over the 12m cross grain bits
Now 1% summer to winter along any grain is to be expected. IN fact I am
seeing 0.1%. So I can only conclude that the sheer weight of furniture
etc etc is keeping it all flat, and the stress is taken up in the wood
If you work on 1% you will be quids in. 0.1% is pushing your luck.
Possibly the best thing is to store it OUTSIDE under cover for a few
weeks - where typical RH will approximate to humid thundery no central
heating type conditions - and then lay it. It will shrink in winter,
with CH, but at least you will be as tight as it can be got.
If it does lift, all is not lost. I had the chippies in for something
else, and they used a reciprocating saw to trim a few mm off where the
whole lot was under huge stress. .
You don't say what size this floor is, but come back and tell me what
0.1% of the dimensions are, in terms of all round gaps
Thanks for your words of wisdom. Much appreciated. Any laminate I have laid
before, I have never once seen any expansion. Especially at the door way
where I never covered the gap but I'd hate to take a chance.
The floor area is 7m x 3.5m. I've mostly left a 10mm gap round the perimeter
of the room and about 5mm gap against the breakfast bar where I just didn't
want a massive gap. It has also been laid under the kickboards so can expand
all it likes under there ;o)
I would have thought it was best to lay it in summer when it had expanded
that way you could lay it with no expansion joints as it couldn't expand any
further or have I read your mail wrong?
well outside and inside RH are the same in summer. and the same outsode
in summer as in winter by and large..fairly fully saturated unless ou
get a heat wave.
Internal RH goes very low in winter when you heat the outside air up.
So we are in essence saying the same thing: lay when its as damp as its
ever likely to be a again.
I think you will get away with it though, and as I said, even if you
don't, its not a complete disaster.
Is this the tile effect stuff? Hardly expands at all IME. I never
leave anything like 10mm. Real wood based stuff is probably different.
Yeah just standard B&Q tile effect laminate.
And +1. I have it all over my house. The conservatory is massive, and
subject to huge extremes of temperature, and I've never had the slightest
problem. That's bog standard B&Q Tileoc. I would estimate that my average
gap is around 5mm, and in places, zero ...
The following website gives the coefficient of thermal expansion for MDF as
That means a 10metre long board will expand 0.12mm for every degree Celsius
(or Kelvin) change in temperature. If the temperature of the board increas
e 40 degrees, the total change in length is only 5mm. That is 2.5 mm at ea
ch end. So a 10mm gap all round is excessive unless you are likely to get
an awful lot of swelling due to moisture.
On 09/01/2017 13:04, firstname.lastname@example.org wrote:
That means a 10metre long board will expand 0.12mm for every degree
Celsius (or Kelvin) change in temperature. If the temperature of the
board increase 40 degrees, the total change in length is only 5mm. That
is 2.5 mm at each end. So a 10mm gap all round is excessive unless you
are likely to get an awful lot of swelling due to moisture.
I think 10mm is way OTT. The beading/skirting is only just that
thickness. You do need a gap = I have seen a laminate floor 'raft' on a
few occasions, although they were in kitchens - so they could have got wet.
Just laid some Wickes tile effect lam with underfloor heating and it expanded only about 2mm over about 3-4 metres, very stable. Although I hear its very sensitive to humidity or damp.
Only problem I have is where it meets a 2m wide patio door I cant find a suitable 2m strip which will allow expansion underneath it, like an upturned L section. Currently have a 10mm gap there! Any ideas?
Thanks Andy, decided to use trimmed L section PVC from B&Q.
HomeOwnersHub.com is a website for homeowners and building and maintenance pros. It is not affiliated with any of the manufacturers or service providers discussed here.
All logos and trade names are the property of their respective owners.