Swelling of laminated floorboards

Hi guys, the floorboards of our investment property started to swell around the edges all over the floor. The house is just one year old and the floor is still under warranty. A guy from the flooring company came for an inspection today and he straight away blamed the tenants for somehow letting the moisture getting underneath the boards. He was confident in saying that even if we get it inspected by the Australian Timer Flooring association they will come to the same conclusion.

But the tenants swear that they always dry mopped the floors and even used towels to wipe off any extra moisture immediately after mopping. And I trust the tenants as they take really good care of the property and always watch out for faults/issues. Moreover, the tenants are raising the question like why would you have such floorboards that swell/bubble even with careful mopping.

What should be my course of action in this circumstance? Thanks in advance.

The damage is not too bad yet. So, it's hard to show them in the photos. But I am worried they might get worse over time.

I know when I did our engineered flooring that I applied the blue bostik membrane (Applied with a roller 2 coats) and then applied the glue and floor. Do you know if the concrete was sealed to stop moisture from below??

Engineered flooring is usually floated, not glued (vs hardwood which is usually glued/nailed)?

Laminate is known for moisture related issues and it will be hard to prove that the moisture wasn't removed immediately. On the contrary, it looks like it stayed for quite a while.

Our engineered floor in Perth was bonded to the slab so it is not drummy when walked on, not sure how the original posters is installed. 2 coats of waterproofing membrane rolled on with a roller then direct stuck using Wacol adhesive.

The flooring company guys said they laid a plastic sheet (or similar) underneath the floorboards to prevent any moisture getting into the floorboards.

It’s caused by tenant. I had the same thing in my own property in the kitchen over period of 2-3 years. Sometime it’s hard to mop every it of moisture esp in kitchen.

I laid the boards myself with foiled underlay and even used anti moisture glue for the kitchen area. Granted I had a newborn which also caused a mess but I would agree with the flooring guy.

These days, in the new house. I have hardwood floor instead. I put waterproof carpet near sink.

I agree if it is sealed underneath then it can only be from mopping. In reality how often are they mopping the floor, its not something that needs doing every week. You are better off just vacuuming with a scratchless head and spot cleaning.

I suspect could be a small spill of 20 cents or 50 cents size pool of liquid and it didn't dry in time and sipped into the gap... That's all it takes.

Which I reckon can be very common especially if you have kids and guest...