Laminate mystery

Hi,

I'm hoping the experts on here can advise! In September we laid Moderna laminate floor over a reinforced concrete subfloor (itself laid in July, so plenty of time to dry out). It's a big floor: 150Msq. We moved in at the start of the month. In the last couple of weeks, the joints in two small areas have begun to spread apart - presently 2mm or 3mm. There's no warping or buckling evident: there's no water nearby, the floor is flat, just the joints - which had been securely clicked together - drifting apart, some at the ends of boards, and some down the side edges.

The house is totally dry, it has underfloor heating and the biggest/heaviest items on the floor anywhere are a fridge freezer and a bookcase. My fitter is a builder but also trained as a chippie and has laid many laminate floors (including bigger rooms than my big through-lounge-diner). It's only happening in two places, and there are only two people living in the house so not that much foot traffic.

Any ideas what might be causing this?

Many thanks

 

When you say totally dry did the fitter used moisture testing equipment before starting. Just because there is no warping does not mean that this is not a damp problem. I would first pick up the area which is parting and test for moisture. what temp is your heating set at ? have the edges been damaged when fitting ? how level is the area on which the boards have parted. these are just a few starting points.

 

Hi there, thank you for responding so quickly, and my apologies in advance for the epic below.

Plan is to wait until after Christmas to take up the floor, partly because we want to wait and watch and partly because I have a disabled partner and the upheaval will need to be carefully managed.

We didn't use a damp meter, but the building is newbuild and the building inspector has been in at every stage, so there is 10cm kingspan on top of the foundation, then 10cm strengthened concrete, and all outside walls are new block and dry lined, interior are just studding and the roof is new. So, moisture at this stage would be a) interesting and b) likely to cause a small nervous breakdown! But, I will suggest we get a damp meter to check it when we take the floor up. It will have to be dissembled from the edge of the adjoining room so that the lengths can be un-clicked and not damaged. Obv, the ones that have spaced will be replaced, and I have some extra to cover that. We're hoping the rest will go back down undamaged.

All the floors were tested with long and short levels before laying. We had tried to polish the concrete floor way back in the summer, but found very fast indeed that air bubbles would cause pock-marking, so we had to lay screed to flatten the areas that had been ground (lesson = if you want a polished concrete floor, get an expert right up-front). The sheer time, screed and effort that went into the re-levelling, I can't believe it would be that, and we can't feel any unevenness or bouncing anywhere. The screed was up to 8mm in some places, but those places are nowhere near where the widening is happening.

Heating is a Magical Mystery Tour. Setting the stats at 21 gives us an ambient temp of 20, but this then varies because we don't yet have a loft hatch, so achieving stability is difficult. That will be sorted next week. It is rare for the floor to feel properly warm: if it does then the rooms are too hot, so the temp we have is more sort of not cold - lukewarm at most. If that makes sense.

 

10cm =100mm. Rule of thumb (but should be tested properly using hygrometer boxes) is 1day per mm up to 50 mm then 2 days per mm after that. So 100mm should take 150 days ( under ideal conditions) for the residual moisture to reach an acceptable level.
Unfortunately, builders and chippies/ joiners aren't flooring specialists and often think that cos the concrete is hard its dry. Not true.
What are the max dimensions of the area?
Were any expansion profiles used anywhere?

 

Trimmer gave spot on advice, once of twice over the past couple of years i have had the lock system fail on me. one with egger and one with sensa but before you go trying to complain to the supplier you will need to take a few rows up to do a proper damp test, if the test
proves a ok then it could be the board.

 

150m2 done by a builder = no expansion joints in all probability.

 

Many thanks for the comments. I've learned a lot about not underestimating moisture & drying time. If anyone has the time to explain an expansion joint, I'd be grateful. Given that we have the u/f heating in place now, and can't take the floor up this side of Christmas for reasons already explained, will the subfloor continue to dry out, or will the laminate on top hold the moisture in it?

 

wood is a hygroscopic material and will move ( expand / shrink) if there are variations in moisture, temperature and humidity in the area in which it is fitted.

 

how did you turn the heating up, per day or just full on

 

My gut feeling is that you have some hotspots with the underfloor heating, maybe the pipes are nearer the surface, this is drying out the boards too much, causing shrinkage? Damp or moisture in the slab would have expanded the boards first before it shrinks and then it would have been more uniform.
IMO
To polish concrete with pot holes isn't a problem, you just use a special sealer product first, then grind and this mixes with the sealer, you then leave the sludge to dry and then you grind again, it's a bit like mixing sawdust from sanding with a resin filler, it matches the concrete and doesn't show.
Should end up with something like this

 

No, and that was my fault, because I didn't decide to try and do that until after it was laid, so it wasn't laid with that in mind.

 

That sounds reasonable. I've not noticed specific hot spots on the floor, but there are some cold spots.

So much wish I'd googled 'flooring expert forum' rather than 'polished concrete floor' back in the summer. I found a reference to this method early on, but no onward links for the sealer and/or the technique. We found a company to hire us the grinder, but (and this should have told us something) it had been sitting in their depot for months and nobody had hired it, and they could offer no advice beyond using successively graded diamonds to grind the floor.

As I say, lesson learned. The important thing is to get it right from now.

I guess my main question moving forward now is whether the floor will continue to dry with the laminate down, or whether I'm trapping moisture in and should take some or all of it up for air circulation. As previously mentioned, I have a disabled partner, so need to minimise disruption and dust. So, it's not ideal if I need to take the floor up, or sections of it up, for weeks to dry, but, if that's what it takes, then that's what it takes.

 

Followed the UF heading company's request and turned it up to heat the slab over two days to make sure it was fully working first, then turned it way down (we moved in in October, and it wasn't cold), then gradually up over the past few weeks.

 

150m2 is a lot of flooring. Does this cover every room in the house or just the ground floor?

I'm not familiar with Moderna but presume it is a click laminate - just a thought that now you know a little more about polishing the concrete and guys on here can give you more help - could you in the future uplift the laminate and utilise it in other areas of the house?

Then you could polish away - as I say just a thought.

 

We have a bungalow: a lot of the renovation work has been to adapt it for wheelchair use. The laminate is throughout except for the bathrooms, which are tiled. Yes, moderna is a click type: I picked it because it is supposed to be suitable for heavy domestic or light commercial, long guarantee (can't remember exactly, but 10+ years) and because it's supposed to be ok with UF heating. Ideally, in future, I'd like to swap it out for something else, as I'm not a big fan of laminate, but we had to bring the project (and the budget) to a close somewhere, so it's a bit of a compromise.