Advice Required Marmox Insulation Boards

[h4rsx]

Hiya,

I've had some Marmox 20mm insulation boards laid down on my conservatory floor today using Bal PTB Flexible adhesive, as I'm planning on installing some under tile heating also.

The boards were laid down by a guy who does tiling, so I left it in his hands, however on checking the boards later this evening, by tapping them, there appears to be alot of hollow sounds, more so than solid sounds (which is where the adhesive is making contact with the boards) there's also some minor flex in the boards around the perimeter of the room which also sound hollowish when tapped.

Am I being paranoid here or does this mean that the boards have not gone down properly? As I realise that the boards are not designed for point loads, flex etc.

The floor was very slightly uneven, but I thought with using the PTB Adhesive, this would eliminate any problems.

Your thoughts would be very appreciated.

[smurf21]

The floor should have been levelled first using a slc then the notched trowel would have a more even surface to spread the addy onto as the boards are a rigid structure they dont bend to floor so unless the fixer has put the adhesive down thick enough to compensate the irregularities you will get voids underneath the boards so unfortunatlly imo not a sound job

[Varley]

You CANNOT tile on the boards if they are flexing mate, tiles will pop off in days. Sorry but that needs to be rectified and it ain't your problem.

[h4rsx]

Thanks very much guys, thats kind of confirmed my suspicions, the floor was only very slight out in places and I know if the adhesive had been applied slightly thicker in those areas, it would've done the job.

Right next question:

How do I go about rectifying it? I pulled up one board with relative ease and saw that the adhesive only made contact in certain places. This then leaves the original adhesive on the floor and a board that has bits of adhesive on it.

Would I be correct in saying that all the boards would need to be lifted, then back buttered and put down over the original adhesive? I can't see the adhesive spreading very well over the original adhesive somehow?

Or

Lay down some flexible SLC, which will fill the groove's in the PTB Adhesive, making the floor flat once again, then re-apply PTB Adhesive again?

Blimey, this is going to work out quite costly, Bal stuff isn't exactly cheap

Again, your thoughts would be appreciated.

[smurf21]

two bags of latex self levelling compound should do the trick(depending on size of conservatory) one 20kg bag and 5 litre bottle of polimer does roughly 3m2 at 3-5mm thick shop around some makes are quite dear i pay around 11 a unit, then relay with flexi addy.
good luck

And you dont have to use bal..