Underlayment is one of those items where we receive many questions on (and that's no wonder, there are so many different products around - all with their own benefits, instructions and promotion slogans).
Last week we had the following (on-line) conversation:
Freddy asked:
Sorry in advance if this is going over old ground. Have recently bought bamboo flooring and will use the "floating method" to install, the underfloor is all old concrete.
Could you give me some guidance on underlay etc. Is it better to use foam and hardboard or the all in one "feltboard type"? Also what kind of expansion gap should I leave as the suppliers told me it is minimal 5/6mm as bamboo is virtually shrinkproof.
Thanks very much for any advice you can give me.
Cheers Freddy
We answered:
Dear Freddy
If your concrete floor is level (may have a gentle sloop of 1 - 2 mm per meter, but no sudden drops or 'hills') it's bes to use a combi-underlayment.
We always recommend to leave 10mm gaps all around, no natural wooden flooring is 'shrink' or 'expansion' proof.
Hope this helps
Wood You Like Ltd
Which resulted in the next question from Freddy:
Thanks for the guidance,(the underlay I mean comes in blocks/slabs and you just cut to fit.The floor is not too bad a little slope running down the hall about 3/4mm over about 2 metres.
I do have to be careful with not gluing the boards to the underlay don't I.
Also do I need to use cork expansion strips?
Thanks again for the help, it's much appreciated.
Cheers Freddy
Our answer:
Hi Freddy
On concrete underfloors it is best to use an underlayment that contains a DPM. The underlayment you mean I don't think will create a continues barrier. Another option for you would be the ticker Timbermate Excell (5mm versus the standard 3mm of the combi)
You're right about having to be careful when glueing the T&G's, any spills on the underlayment can 'strop' the floor when it 'moves' during the seasons.
Cork expansion strips just fill up your expansion gaps! You don't need them.
Hope this helps
Wood You Like Ltd
Freddy replied as follows:
Thanks very much for the advice, it's very much appreciated.
Cheers
Freddy
Feel free to ask your own question, either by leaving a comment underneath this post - or any other, or in our category 6 - in the relevant FAQ post your query is about:
Benefits, Preparations, Installations or Maintenance and After Care
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