I've been to see a job today where the tiles have lifted (i never laid them, i was too busy so the customer had to get someone else) 300 x 300 ceramics on ordinary ply. don't know what thickness yet. the ufh heating wire is of course ruined too, it was switched on fully almost immediatley after tiles were laid the customer is getting a joiner to change boards to 25mm marine ply and after me recommending she has got some new ufh cable from u-heat. i will be priming the boards prior to re-laying the tiles with rapid set flexi. would you lay any differently? i've done this many times but just checking due to the tiles already failing. i know it's prob due to heating on straight away and wrong ply. cheers guys. mike

I always like to lay the matting on an insulation board or a cement board so if you could add that into the equation that would be good. The SLC and addy stick much better to the boards than ply.

I would over board with a cement board as well if given the choice, also I woulnt prime the ply as the manufacturer I use (Mapei) doesnt recommend it. May be different with other brands tho. 1 last thing, make sure that the heat mat is recommended for ply

Originally Posted by Brian J

I always like to lay the matting on an insulation board or a cement board so if you could add that into the equation that would be good. The SLC and addy stick much better to the boards than ply.

Beat me to the punch

6-10 mm wedi over the ply,should act as insulation aswell,,or so im told.Prime the ply and fasten wedi with adhesive and mechanically.place underfloor heating then 2 part mappei levelling compound over the wires....Then ditra to top it all off.This is the system the contractor i work for uses on very high end properties in london and he has not had any complaints,,,

i thought you coulnt put slc over the ufh as its on ply not concrete? and there s no matting , it's just the cable only type

Slc on ply Is fine as long as it's specified for that purpose.....

i tank and tape all the wedi first in the joints and corners,,,I am new to this particular system,what is the problem with slc and ply?

Originally Posted by russ

i tank and tape all the wedi first in the joints and corners,,,I am new to this particular system,what is the problem with slc and ply?

i was led to believe it wasnt flexible enough unlike flexi addy. also i've never seen it mentioned on the instructions of the different slc's i've used

Use the Mapei Fibreplan.

i'll try get that tomorrow thanks john

Originally Posted by timeless john

Use the Mapei Fibreplan.

Get Mapei Renovation screed, its half the price and awesome stuff to use.
ultraplan renovation_uk.pdf

Originally Posted by timeless john

Use the Mapei Fibreplan.

Last time I asked for Fibreplan, was asked if it was a diet, walked out

I often use Ardex Arditex NA over slc on ply, but would always prefer to overboard prior to installing the UFH.

Originally Posted by tectonicfloors

I always like to lay the matting on an insulation board or a cement board so if you could add that into the equation that would be good. Place under floor heating then 2 part mapped leveling compound over the wires. Thanks.

that's how i did it, a long time ago i may add, this is an old thread

Originally Posted by tectonicfloors

I always like to lay the matting on an insulation board or a cement board so if you could add that into the equation that would be good. Place under floor heating then 2 part mapped leveling compound over the wires. Thanks.

That is uncanny Bri's post no 2 is word for word the same as yours, apart from the last sentence. I know they say great minds think alike, but I wonder.........Ummmm?????

Originally Posted by Mike

I've been to see a job today where the tiles have lifted (i never laid them, i was too busy so the customer had to get someone else) 300 x 300 ceramics on ordinary ply. don't know what thickness yet. the ufh heating wire is of course ruined too, it was switched on fully almost immediatley after tiles were laid the customer is getting a joiner to change boards to 25mm marine ply and after me recommending she has got some new ufh cable from u-heat. i will be priming the boards prior to re-laying the tiles with rapid set flexi. would you lay any differently? i've done this many times but just checking due to the tiles already failing. i know it's prob due to heating on straight away and wrong ply. cheers guys. mike

I know this is an old thread but..

When I install a heating mat down, first I trowel Mapelastic HPC over the plywood.."waterproof/anti fracture membrane"

Then I stick the mat or mat's down leaving 4-6 inches on the outer perimeter of the room.

Then I secure some 1/2" inch Cement board down with thinset and screws around the perimeter of the room..

Then mix some Modified Thinset with some fine sand and water and fill in the center between the 1/2'' boards using them to screed off of...

After it dries for 24-48 hours depending on heat/cold apply another coat of Mapelastic HPC..Let dry and start tiling on a flat sturdy floor..Read directions on materials used always..

Originally Posted by Mortarforker

I know this is an old thread but..

When I install a heating mat down, first I trowel Mapelastic HPC over the plywood.."waterproof/anti fracture membrane"

Then I stick the mat or mat's down leaving 4-6 inches on the outer perimeter of the room.

Then I secure some 1/2" inch Cement board down with thinset and screws around the perimeter of the room..

Then mix some Modified Thinset with some fine sand and water and fill in the center between the 1/2'' boards using them to screed off of...

After it dries for 24-48 hours depending on heat/cold apply another coat of Mapelastic HPC..Let dry and start tiling on a flat sturdy floor..Read directions on materials used always..

wrong way round imo, what's to stop you piercing the ufh when overlaying? personally I lay the backer boards then matting then slc.

Originally Posted by doug boardley

wrong way round imo, what's to stop you piercing the ufh when overlaying? personally I lay the backer boards then matting then slc.

I use a LOUD MOUTH..You hook it up to the wires during installation...It tells you if the wire has been cut ....And I also use a fiberglass trowel to skim over the UFH..Make any sense now..Doug? No cut wires No self leveling cement that "REALLY DOES NOT SELF LEVEL" You have to push it into place...haha..self leveling is for home owners that know no other way..

Originally Posted by Mortarforker

I use a LOUD MOUTH..You hook it up to the wires during installation...It tells you if the wire has been cut ....And I also use a fiberglass trowel to skim over the UFH..Make any sense now..Doug? No cut wires No self leveling cement that "REALLY DOES NOT SELF LEVEL" You have to push it into place...haha..self leveling is for home owners that know no other way..

I'm with Doug on this one . but its interesting different parts of the world different methods. and slc will level if done right

I am with Doug & Jay too.
The underfloor heating system goes on top of the cement board.
Cement boards / Construction boards etc have insulation inside them and will stop the heat passing onwards into the room above.
Cement boards first then the underfloor heating system goes on top.

Originally Posted by Mortarforker

I use a LOUD MOUTH..You hook it up to the wires during installation...It tells you if the wire has been cut ....And I also use a fiberglass trowel to skim over the UFH..Make any sense now..Doug? No cut wires No self leveling cement that "REALLY DOES NOT SELF LEVEL" You have to push it into place...haha..self leveling is for home owners that know no other way..

Really??, good to know I've been doing it wrong for 30 years then.

Originally Posted by doug boardley

Really??, good to know I've been doing it wrong for 30 years then.

UFH matting has been around for 30 years? Really? Right way/Wrong way..There are many ways to do the same job..Im not saying any way is wrong or right..It's up to the installer to be inventive and try new idea's..Did'nt mean to ruffle any feathers..Cheers..

Originally Posted by Mortarforker

UFH matting has been around for 30 years? Really? Right way/Wrong way..There are many ways to do the same job..Im not saying any way is wrong or right..It's up to the installer to be inventive and try new idea's..Did'nt mean to ruffle any feathers..Cheers..

I was actually referring to slc'ing, to long in the tooth to have my feathers ruffled.

Maybe this has been read wrong..

I take it as cement board cuts around the perimeter of the room and then you screeded over the ufh.. so in theory it is the same as using the SLC's that we use in the uk..but you use thinset instead.. Have i got that right.?

So you are not laying cement boards over the ufh, just around the perimeter as screed levelling heights..?

Originally Posted by Dave

Maybe this has been read wrong..

I take it as cement board cuts around the perimeter of the room and then you screeded over the ufh.. so in theory it is the same as using the SLC's that we use in the uk..but you use thinset instead.. Have i got that right.?

So you are not laying cement boards over the ufh, just around the perimeter as screed levelling heights..?

Correct..I have had too many failures with self leveling compounds..They either don't stick to the primer..Or too much water or not enough water...it has to be the right enviroment for it to work perfectly..I use thinset because I can control how wet I make it and how I can burn it into the flooring beneath..Then I alway's let it dry all the way...Then continue to install a membrane over the top of it..This is just my method and I let my customer know that I warranty my work for 5 years..Everyone has there own way..But this is mine and I trust it..

I thought some had read your method wrong..

We have Fibre modified slc's here now and they are perfect foe UFH etc.. really good compared to what slc's were 2 yrs ago or so..

Originally Posted by Dave

Maybe this has been read wrong..

I take it as cement board cuts around the perimeter of the room and then you screeded over the ufh.. so in theory it is the same as using the SLC's that we use in the uk..but you use thinset instead.. Have i got that right.?

So you are not laying cement boards over the ufh, just around the perimeter as screed levelling heights..?

I am installing a heating mat this week..I will take pics of how I do it and post them..

my apologies for mis-reading your post.......but I'll still be using the slc's that I use and trust

That would be good... .. look forward to them.