Fiberboard Underlay

15 May 2007
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United Kingdom

We have a friend that is willing to give us a surplus of fiberboard underlay that was from B&Q - the 6mm green stuff.

We are just about to fit our engineer flooring and was wondering if this would be OK to use on a chipboard subfloor. If you do not recommend this, could you please advise on a good sound proofing and thermal barrier.


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In our experience these green fibreboards could make tour floor feel bouncy especially when it is not really smooth, flat and even.
If that's the case in your situation you could be better of with Timbermate Duratex.
Thanks - I thought this would be the case!

Sorry for the long post here.....

We have today checked out the floor after screwing all the loose chipboards boards down that were squeeking etc. We also checked out the level of the floor and there are a few areas which concern me.

We have a large area in the lounge travelling the width of the room (4m)with a width 2m wide which at it lowest point is around 10mm deep.
The other areas are at the top of the stairs (from the ground floor) and bottom of the stairs (to the 2nd floor) of the town house which also have a similar dip depth of 10mm but the area is about 1mx1m each.

I know there have been several posts here and around the web on what to do in these situations and there are several options:

- Rip up the T&G chipboard and pack up the joists and re-lay. There are several reasons we don't want to do this. If we had to do this I wouldn't bother and just carpet.

So what are the alternatives?...

- Lay a latex self-leveling screed on these areas. What are the issues with this?

- Lay the flooring directly on the chipboard, glue and/or secret-nail it so it following the dips in the floor - unsure what the end result would look like her?. Also, unless you can nail through the underlay as mentioned in the previous post, I assume underlay is not an option?

- I have also seen that you should not secret-nail on to chipboard as it 'explodes' - they recommended laying ply and then the floor on top for this. Would require thick 18mm ply to cover the dips to stop it bowing which means the fininshed floor would be 18mm ply + 15mm Eng. Floor + (poss. 3mm underlay) = max 36mm floor!

- Ditch the idea and carpet!

Answers to the options above would be very welcome for the best results - unless anyone has suggestions.


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Just checked out the leveling of uneven floors wiki on here.

I assume the other option is the fibre-reinforced screed. Checking the details of Uzin 175 product (as mentioned in the wiki), it states it can be used on wood-floor rather than just Ply as the F-Ball does. (

Is this the case - could I use this straight on the chipboard - would I need any primer for the Uzin 175?

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