Problem with Mapei Renovation Screed and Wunda Overfloor panel

[Clifflev]

Hello. I have had Wunda overfloor heating panels installed to approx 70m2 area. When the flooring company came to lay our quickstep laminate arte floor tiles (640x640) they said the floor wasn't level enough as many of the underfloor heating pipes where raised about 2-3mm above the aluminium boards and concerned that the 2mm underlay would not be sufficient to sort it.

I contacted Wunda who advised to lay Mapei Eco Prim Grip and then Mapei Ultraplan Renovation Screed. This was done in about a 5 hour timeframe one night last week (by the same people laying the new floor)

When the floor guy came the next day, there were a few sections where the screed went under the Wunda heating panel and raised them and the pipe up quite high - about 1.5cm. The screed was dug out and the pipe secured down and infilled with more screed (sorted). They came the next day but found a larger area had blown up in the hallway - this has been dug out and is waiting to be filled again (its now xmas so have to wait for them to come back in the new year)

Now, when walking across certain areas i can hear cracking and there are some small raised areas (about 5cm x 5cm) - like an air bubble.

I'm concerned why there are air bubbles?, perhaps the screed was laid in a bit of a rush? i.e the primer didn't have time to dry sufficiently?

whats the best thing to do here? Can an extra layer of screed go on top of what has already been laid? Wunda recommends 5mm but i dont think this has been achieved, i reckon i have 2-3mm. Going on top of the screed is 2mm quickstep insulation (breathable, designed for underfloor heating) and then 9.5mm quickstep laminate arte floor tiles (640x640)

The flooring company have been helpful and assured me they want the flooring to go down nicely and want to do a good job - i just want some peace of mind as dont want issues further down the line.

Many thanks for your help and advice.

 

[Qwerty]

I'm not convinced that this scenario is suitable for mapei ren screed. I would advise that you call mapei technical helpline and ask for their assistance

 

[afright]

Screeding another layer will not sort out the issue if its cracking underfoot as blocko has said call the Mapei tech guys.

 

[Clifflev]

we consulted the company where we purchased the UFH from (Wunda Floor Heating), they're product guide says to use the Mapei products. I'm speaking with the flooring company in a couple days to see what they suggest as a way forward

 

[Ajax123]

If these panels are alluminium foil this reacts with the hydroxide ions in the wet cement screed and produces hydrogen gas bubbles which sounds very similar to what you are describing. If it is all still solid it is likely that this is not an issue but I agree with previous comments that I am not convinced that this system is suitable for the Mapei Reno screed... What do Mapei say?? The hydrogen production is stopped by the application of she'd loads of primer or even PVA which is one of the few applications for which PVA is actually suitable. It MUST be fully dried though so if all this was done in a five hour period it is impossible that the primer would have dried.... Not just unlikely bit impossible. It takes about 4 hours to set and dry properly on a screed. On a non absorbent surface like foils backed board this is more likely to be 24hours minimum....

 

[Clifflev]

hi yes they put down the Mapei Eco Prim Grip first - then the renovation screed - this was done last Friday and it has all dried solid.

 

[Ajax123]

hi yes they put down the Mapei Eco Prim Grip first - then the renovation screed - this was done last Friday and it has all dried solid.

that being the case and assuming Mapei are happy you could overlay the existing with new screed. If they ( not you because her could be a warranty issue) chip away the top f one of th bubbles it should be slightly honeycombed inside. This is where the hydrogen gas has bubbled up though framing the " air bubble" you speak of. This is a good way to test it. If you have any pics I might be able to confirm without the chipping away bit. I have seen this on many occasions with flowing screeds.

 

[Clifflev]

Hi Ajax123 and thanks for your reply. I will take some photos

just thinking ahead, once the air pockets are resolved, if there are areas where the floor levels are still not right for laying our laminate floor tiles, can further layer of screed be laid on top?, should more primer be applied?

 

[Qwerty]

I'm under the impression that it will all have to come up?

 

[Clifflev]

No I don't think it's the case it all has to come off, as long as the few sections where I have these raised areas/air pockets can be chipped out and in filled with new screed it should be ok

 

[DHTiling]

Hi..

Is there any deflection under the panels?

Was the Renovation screed mixed with the correct amount of water.?

Was the renovation screed laid to min 5mm depth ..?

Lastly , is the heating on. ?

 

[Ajax123]

Hi Ajax123 and thanks for your reply. I will take some photos

just thinking ahead, once the air pockets are resolved, if there are areas where the floor levels are still not right for laying our laminate floor tiles, can further layer of screed be laid on top?, should more primer be applied?

yes and yes but the primary issue is whether or not the Mapei gear is suitable for the application. You could end up just throwing good money after bad and still have a system that is not suitable. You need a conversation with Mapei technical before doing anything further. The "air bubbles" are classic symptom of reaction between hydroxide and alluminium. Pics will confirm if this is a correct diagnosis. N further reaction will occur once the screed has hardened and dried.

 

[Clifflev]

i spoke with the mapei technical guy today. i explained about the Wunda under floor heating product (the overfloor system) and that it has an aluminium top to which he acknowledged he knew the product and what i was referring too. I explained the air pockets with cracks and that they had occurred in a few areas and he said its likely happened because the screed is too thin in those areas. He agreed an extra screed can go on top but must put down the Mapei Eco Primer Grip first - he said the primer was quick drying.

I'm pleased the mapei guy knew the product i was talking about and gave me no reason to be concerned that we have used the wrong mapei products on the Wunda overfloor heating boards with aluminium top.

My view is that an extra screed layer is needed as i recall counting 14 bags of renovation screed which covers 84m2 at 3mm thickness whereas i have 75m2 and needs 5mm thickness.

I'll speak with the flooring company tomorrow and see what solutions/options they propose as they have to lay my new laminate flooring and do a proper job - after all I am paying them money to do this!

 

[Clifflev]

Hi All

Just to give some positive feedback. Had a few phone conversations with Mapei Technical support between xmas and new year, and to my surprise they made the trip down from Birmingham to my home in Hertfordshire to see what the cause is with the screed (I didn't realise they look at these forums!)

The promptly arrived when they said they would (approx 3 hour trip!) and confirmed that the screed was applied too thinly and that the primer wasn't given enough time to dry - this is what many areas had "blown" and not adhered to the subfloor. They also waited for the person who did the screed to advise him how he should correct the issues which the floor company are now putting right

So i just wanted to say a *big* thankyou to the tech guys from Mapei for taking the time to understand the issue and coming all that way to see us and giving us reassurance that it can be resolved

Regards,
Cliff