Fitting ufh for 1st time, advice please??

[aflemi]

I am doing a customer's bathroom and this includes ufh. They have supplied Thermonet heatmat. The situation is:
Solid concrete floor approx 4sqm, previously laid with vinyl tiles on bitumen for past 30+ years, tiles came up easily floor seems stable.
Slight complication is plumber has dug up an area of floor approx 130mm x 800mm x 80mm deep at the wall edge to relocate radiator pipes.
I have a few questions, bit unsure as never laid ufh before.
If the 'dug up' area is relaid with sand/cement, would I have to leave it 80 days to fully dry? (customer will explode.....) or is there a de-coupling product I could use? if so I assume it would just require to be used over the affected area with some margin?

I understand the procedure is to lay insulation boards using flexible adhesive?, lay heating mat and cover with slc (I prefer to tile over rather than risk catching wires, is that correct? Thermonet recommend Mira x-plan.
I am slightly unsure of procedure for checking resistance while laying the mat, I have a resistance meter, do I temporarily plug in the connecting wires to check (and record for warranty) regularly?

I thought I wascomfortable with the procedure until I read thermonet's diagram for laying on solid floor
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where they recommend sand + cement screed over insulation then the matting.
I appreciate this is long winded but need to have it right and after reading their instructions I think I am more confused than before.
Thanks in advance for help.

 

[dagger]

the biggest problem is the bitumen, but wickes do a patch repair mortar that is rapid setting and dries in 2 hours!

 

[aflemi]

thanks dagger, i assume you mean to fill the plumber's hole (so to speak). so I would be ok to lay as normal as soon as wickes repair mortar is dry?
Any suggestions on other issues, also on the bitumen, which i am concerned about now.. Surely this must be a common occurence..... If it's any help, it is an extremely thin layer and it's only on the area which had the vinyl tiles laid.
Help much appreciated, i need to be ordering slc and insulation boards etc so am running out of time a bit...

 

[dagger]

if its only a thin layer over concrete, remove as much as you can and use a S2 adhesive to stick down the backer boards!
i.e keraquick and latex plus (super sticky stuff!).
then carry on as usual, but that said, it is always a good idea to call the adhesive manafacturer for advice on bitumen!

you may even be able to fibreplan it, call tech support!

but the heat mat will defenitly liven up the bitumen if in close contact!

 

[aflemi]

thanks, dagger, understood but can you or someone clarify what an s2 adhesive is please?
Also on the patching, what would the normal drying time be for a sand and cement substrate? Is it 1 day per mm as I thought on original post?

 

[dagger]

thanks, dagger, understood but can you or someone clarify what an s2 adhesive is please?
Also on the patching, what would the normal drying time be for a sand and cement substrate? Is it 1 day per mm as I thought on original post?

S2 adhesive is usually a bag of flexi rapid set adhesive that comes with a bottle of "milk" you do not add water,keraquick is s1 add latex plus to it and its s2.and according to Lafarge sand and cement screeds are 1mm per day.best of luck. but going back to the original part of the post you MUST remove all the bitumen coating back to concrete, i asked on your behalf to know for the future!

 

[dagger]

hss will hire you a scarifier or a scabbler, basically its a floor grinder!

easy to use but a bit messy.

 

[aflemi]

Cheers, thanks for help. I have a heavy duty wire bush attachment for the angle grinder which I'll have a go with, as it's an extremely thin layer. With the insulation boards it should be ok, I've read several posts advising simply roughing it up and SBR prime so feel ok about that.

 

[Ajax123]

Because an area has been"dug out" and replaced you effectively have two joints in your substrate. Whilst I would expect no vertical movement I would expect some horizontal movement due to thermal expansion and contraction. The joints are supposed to be reflected through the tiles. Clearly this would be impracticable not to mention look awful. I think this is one where a decoupling mat is appropriate. It will take account of the "different" substrates and then you would not have to wait for the repair to dry either so straight ofroward sand cement mixed in a bucket would do the trick. G-mat says it is sutiable on asphalt - I guess the other are as well. It would also help avoid all that tiresome preparation

 

[aflemi]

Thanks Ajax, I seem to have 2 issues here, the bitumen and plumbers digging.. If I go back to original sand/cement making good, what would the correct procedure be? My guess is...
1/Roughen/remove Bitumen as much as poss.
2/Prime with SBR.
3/Lay uncoupling membrane with S2 flexible adhesive?
4/Lay ufh mat.
5/Cover ufh with flexible adhesive/slc.
Finally 6/........LAY TILES using flexible everything...

Please could someone confirm or offer corrections as I'm due to do the floor tomorrow......
Many thanks.

 

[aflemi]

Because an area has been"dug out" and replaced you effectively have two joints in your substrate. Whilst I would expect no vertical movement I would expect some horizontal movement due to thermal expansion and contraction. The joints are supposed to be reflected through the tiles. Clearly this would be impracticable not to mention look awful. I think this is one where a decoupling mat is appropriate. It will take account of the "different" substrates and then you would not have to wait for the repair to dry either so straight ofroward sand cement mixed in a bucket would do the trick. G-mat says it is sutiable on asphalt - I guess the other are as well. It would also help avoid all that tiresome preparation

Spoke to both Gemini (G-Mat) and Schluter. Both basically same idea but Schluter were slightly more informative. The question of suitability over bitumen is really down to the adhesive/bitumen contact. (I decided to lay a slurry coat after reading advice on here, Mapei were particulary negative on using their products on it.). Schluter say ditra should be tiled onto directly and any movement/cracking underneath will be absorbed so I am following this order:
1/ Slurry coat.
2/ Insulation on rapidset.
3/ heat mat
4/ slc/rapidset adhesive covering
5/uncoupling membrane on rapidset
6/adhesive
7/tiles
(everything flexible of course)