Dampness causing Marmoleum to bubble

[ryanline79]

We recently opened a business and put down a marmoleum floor-covering on an old concrete floor slab (to three rooms).
There were trenches cut in the concrete floor-slab for heating and these were reconcreted (prior to laying marmoleum).
There was slight dampness in the trenches when (due to time constraints) we put down the marmoleum. The marmoleum was put down in Feb and as we feared it has began to bubble within a month. It got progressively worse but seems to only following the trench.
We cut out some sections of the bubbled marmoluem and have been covering these areas with mats for the last 2 months. However the concrete in these trenches doesn't appear to be drying out. We have confirmed that there is no leak to the piping in the building.
We were wondering whether it would be possible to put a sealer of some kind to the concrete where the marmoleum has bubbled up and then put down new strips of marmoleum.
Has anyone experience of a similar issue with marmoleum and would they have any advice on a solution?

 

[Leo]

Did you compromise the DPM cutting the trenches?

 

[ryanline79]

This property was restored in the early 70s (and is a much older town centre building of stone rubble) so probably doesn't have a DPM. It is likely that the trench has upset whatever "natural" DPM was in place. Areas outside of where the trenches were dug did seem to have dried out sufficiently and it only seems to have been the areas where the trench had been dug that there was an issue of dampness. The builder we employed had filled in trenches without us knowing whether a DPM had been installed or not.
As I was saying would it be possible now to put a sealer on top that may act as a DPM on top of the floor? Or does anyone have any other advice.

 

[ryanline79]

Hi ryanline,
Did you have an engineer employed to check the construction details of the contractor.

What you can do is get a reading on the moisture content of the floor slab in a number of locations. To lay Marmolenum the floor slab should be dried out to a minimum moisture content (this will take a number of week after pouring the concrete), Forbo flooring company should be able to give you this. maybe what has happened the marmoleum was put down to quickly and held the moisture in the floor.
You can
1 take up the floor get a dehumidifer and keep checking the moisture content to see if it dropping or
2.maybe the best solution and peace of mind is lay a liquid DPM under the marmoleum to all the floor area but this will cost more.

EDIT on FORBO Website
Installation

Colorex SD/EC can be installed on approved substrates of all grade levels. The substrate should be prepared with a self-levelling compound and have a residual moisture content of no greater than 2.5% CM at the time of installation. In case of rising damp, we strongly recommended that you install a proper moisture barrier.

Thanks for the response Also,

We are leasing the property, the landlord renovated the heating system and the new marmoleum floor covering was part of our scope. So the builder dug and refilled the trench as part of the landlords scope.
Our flooring guy was fairly happy to put down the marmoleum (although the was an indication of dampness to the trench) and as above we were under pressure to get the business up and running.

We have since removed some of the marmoluem in a few areas to let it dry out. We are considering putting down a liquid DPM but were wondering whether we would get away with just putting it down above the trench (were the marmoleum has bubbled) and therefore not have to take up all the floor covering.
Its a tricky one to give advice on I know, was just wondering had anyone came across anything similar.

 

[Leo]

What you can do is get a reading on the moisture content of the floor slab in a number of locations. To lay Marmolenum the floor slab should be dried out to a minimum moisture content (this will take a number of week after pouring the concrete)

It's not a new slab.

How long were the trenches left to dry before the covering was put down?

You may need to engage a specialist damp treatment company to remedy this.

 

[ryanline79]

It's not a new slab.

How long were the trenches left to dry before the covering was put down?

.

About two months.

Looking at two options at the moment - sealing the concrete above the trench with a liquid DPM and replacing the damaged marmoleum or the unfort more expensive option of taking up all the marmoleum (on a phased basis by room) and putting a liquid DPM on the floors and putting a new floor covering on it.

If anyone has any other advice Id appreciate it.