Laminate Underlay Up Walls?

paperclap

Hi all,

Not sure if I am overworrying, or not worrying enough here!

We are laying laminate down.

We've removed the old laminate and green fibre board underlay.

Beneath, we have red/brown thermoplastic tiles, bitumen, then concrete. No doubt the former two have asbestos, so won't be removing. It is pretty flat throughout.

After removing, I've used a Valiant moisture meter to test the moisture of some areas of the concrete floor. Some areas of the external walls are damp (0.4-2%). Area by the front door is damp (around 8%), but believe this is due to missing mortar. Area by the conservatory sliding doors (living room side) is damp (around 8%)... but not sure how. Previous owner has removed the tiles in this area (maybe they broke away when fitting the sliding doors?) and re-screeded. Screed has minor hairline cracks.

While I will try my best to rectify these damp issues... I really don't want to be doing it now, as we're in the middle of laying laminate. Living in a building site is not fun.

Will we be okay to lay underlay over the top now, and fix these (hopefully "minor") issues next summer?

Now, we've chosen to use Quickstep's Thermolevel underlay. 5mm foam and foil-backed, to act as a damp proof membrane. Weirdly, they state the foil side goes up (contrary to what everyone else says). Anyway, it is in rigid folding boards, so can't go right into the wall without causing noise, and can't go an inch or two "up" the wall. Is this going to be an issue? Worth noting that in this area there are no tiles and bitumen, as these would have been fitted prior to the original skirting board. So, just bare concrete around the perimeters of the rooms. Most sitting around 0-0.3% moisture.

https://www.quick-step.co.uk/en-gb/accessories/qsudltl9_thermolevel

Thanks!

FreeBear

First point - A damp meter will only give a true reading when used on untreated timber. When used on concrete, plaster, or any other building material, the numbers are meaningless. At best, these meters can be used to give a comparative reading that might indicate possible damp.

As for the underlay, leave a gap of 10mm around the edge of the room, and you'll be fine. Do the same with the laminate, and the skirting board will hide the gap.

paperclap

FreeBear said:

First point - A damp meter will only give a true reading when used on untreated timber. When used on concrete, plaster, or any other building material, the numbers are meaningless. At best, these meters can be used to give a comparative reading that might indicate possible damp.

As for the underlay, leave a gap of 10mm around the edge of the room, and you'll be fine. Do the same with the laminate, and the skirting board will hide the gap.

Thank you!

So I won't need to worry about any damp around the perimeters of the room?

And presumably the other bits of damp that can be fixed (e.g. by the door) can wait until next summer?

FreeBear

laurencewhymark said: And presumably the other bits of damp that can be fixed (e.g. by the door) can wait until next summer?

If you are wanting to treat the damp in the concrete floor, best to go it before the laminate goes down (depending on the source of the damp). I suspect some of the damp is just condensation due to the area in front of the doors being slightly colder than the rest of the room. Some bitumastic paint will seal it - There should already be a damp proof membrane within the floor. Exterior repointing can (should) wait until the weather warms up a bit.

paperclap

FreeBear said:

laurencewhymark said: And presumably the other bits of damp that can be fixed (e.g. by the door) can wait until next summer?

If you are wanting to treat the damp in the concrete floor, best to go it before the laminate goes down (depending on the source of the damp). I suspect some of the damp is just condensation due to the area in front of the doors being slightly colder than the rest of the room. Some bitumastic paint will seal it - There should already be a damp proof membrane within the floor. Exterior repointing can (should) wait until the weather warms up a bit.

I had't wanted to go down the bitumastic paint route as it takes forever to dry (well, 3 days).

Is it really possible that the damp areas around the conservatory door are condensation... or "sweat"?

There's no damp proof membrane in our house, from what I know. We've a damp course... but no membrane. From what I've read, these thermoplastic tiles and bitumen were the damp proof membrane back in the day (it's a 1955 build)!

paperclap

FreeBear said:

laurencewhymark said: And presumably the other bits of damp that can be fixed (e.g. by the door) can wait until next summer?

If you are wanting to treat the damp in the concrete floor, best to go it before the laminate goes down (depending on the source of the damp). I suspect some of the damp is just condensation due to the area in front of the doors being slightly colder than the rest of the room. Some bitumastic paint will seal it - There should already be a damp proof membrane within the floor. Exterior repointing can (should) wait until the weather warms up a bit.

If I were to seal those areas (and maybe even the perimeters of the rooms) where would the damp, if any, go to? It would be trapped and start to be even more of an issue, wouldn't it?

Norman_Castle

Were there any signs of damp on the now removed green boards?

paperclap

Norman_Castle said:

Were there any signs of damp on the now removed green boards?

Yellow staining on the back of the green boards by the front door... where I believe it is either due to missing mortar externally, or a roof leak between the cavity wall (we need a new roof... which I'm planning on doing next year).

The other areas that I thought may be "damp" (e.g. conservatory area, etc), there was no staining on the back of the green boards.