Ply floor - UFH - Ditra mat - Tiles

[mog]

Hi there

1st time poster - long time lurker so be gentle!

I'm in a bit of a quandary and would be grateful for some advice.

Currently have a new ground floor extension being completed (kitchen and bathroom) around 25 sqm in total.

The kitchen part is 18mm ply (external I'm told but not sure) and the joists underneath have been made narrower to provide greater stability with extra noggins all around esp at joints and with screws at every say 200mm. The floor is stable and there is no movement. I've noted however that in some places the ply has expanded (maybe some water dropped) at the edges so that some are overlapping other joints (laterally not vertically). So will have to ask builder about that.

I intend to install either retrofit water based or electric mat UFH and then porcelain tiles on top.

My questions are as follows:

1. I am worried from reading on forums that 18mm ply may not be a sufficient enough base and further ply can expand and contract at different rates to the tiles which can cause cracks. I therefore intend to put Warm Up insulation boards on the floor and then the electric UFH on top. Is this sufficient or do you think I need to use a ditra/durabase mat product?

2. If I go for the retrofit water based UFH (from Wunda floor) on top of the ply these pipes comes embedded in a polysterine insulation mat which I can tile direct on top of. Do you still think I need ditra/durabase over this?

3. Assuming I go for electric what would be the best method? i.e. insulation board then UFH then Ditra or vice versa? Also what adhesives are recommended?

4. I have purchased BAL flexi tile adhesive for the tiles - is this suitable for ditra/surbase mat?

Sorry for all the questions but the builder seems a bit clueless and just wants to finish the job quickly and is relying on me to tell him what I want so I'm having to learn very fast!

Thanks in advance all.

M

 

[Qwerty]

My advice is to get tradesmen in who are experts in their trade.

Have you seen the builders abilities in this type of work? His cluelessness is worrying and ultimately could cost you thousands if his methods are incorrect.

Whichever route you want to go down you will need to ensure floor is solid, sound condition and correctly primed (not PVA!). Insulation board, UFH, self levelling compound then tiles is my advice. No real need for Ditra in your circumstance. You will require a bagged cement flexible single part adhesive for the project though

 

[mog]

My advice is to get tradesmen in who are experts in their trade.

Have you seen the builders abilities in this type of work? His cluelessness is worrying and ultimately could cost you thousands if his methods are incorrect.

Whichever route you want to go down you will need to ensure floor is solid, sound condition and correctly primed (not PVA!). Insulation board, UFH, self levelling compound then tiles is my advice. No real need for Ditra in your circumstance. You will require a bagged cement flexible single part adhesive for the project though

Thnks for the response.

The builder seemed ok when I saw his previous work. But now if I ask anything remotely technical ie. Ditra he seems to have passed the buck over.

Any reason why you think I don't need Ditra? I though as I'm on ply (albeit therma boards on top) it'd be necessary?

thanks

 

[beanz]

I don't think I'd be happy tiling directly on to polystyrene!?!
if you were tiling directly to the ply, I'd recommend Ditra, but I think the thermal boards will negate the need for this.
I'm not sure about your lateral overlapping!?! Has there definitely been movement? Or were they layed slightly staggered, due to the room being out of square?

 

[Qwerty]

I would be avoiding tiling to any wet UFH insulation like the plague. My post was directed towards the electric UFH route.

 

[mog]

I thought the warmup boards are concrete backed like tile backer boards?? I thought it odd at first myself but that's what everyone said you have to do...

 

[Stef]

This might help.
http://www.schluter.co.uk/underfloor_heating.aspx

Haven't used it personally but I have heard good things about it..

 

[One Day]

Don't use Wunderfloor. It's far from wunderful for tiling.
I'd suggest Ditra Heat-E as it would solve all your issues in one go.
Bekotec Therm is great but expensive.

 

[mog]

Would I still need insulation boards underneath the heat-e ? I got a quote for it and it's about twice as more expensive than standard warm up. Plus then I imagine you'd still need the insulation beneath it.

I'm swaying towards insulation, ufh, tiles ..

 

[beanz]

Yes, you'd still need the insulation..

 

[mog]

Thanks. So the consensus is No need for ditra here?

 

[TJ Smiler]

Hi there

1st time poster - long time lurker so be gentle!

I'm in a bit of a quandary and would be grateful for some advice.

Currently have a new ground floor extension being completed (kitchen and bathroom) around 25 sqm in total.

The kitchen part is 18mm ply (external I'm told but not sure) and the joists underneath have been made narrower to provide greater stability with extra noggins all around esp at joints and with screws at every say 200mm. The floor is stable and there is no movement. I've noted however that in some places the ply has expanded (maybe some water dropped) at the edges so that some are overlapping other joints (laterally not vertically). So will have to ask builder about that.

I intend to install either retrofit water based or electric mat UFH and then porcelain tiles on top.

My questions are as follows:

1. I am worried from reading on forums that 18mm ply may not be a sufficient enough base and further ply can expand and contract at different rates to the tiles which can cause cracks. I therefore intend to put Warm Up insulation boards on the floor and then the electric UFH on top. Is this sufficient or do you think I need to use a ditra/durabase mat product?

2. If I go for the retrofit water based UFH (from Wunda floor) on top of the ply these pipes comes embedded in a polysterine insulation mat which I can tile direct on top of. Do you still think I need ditra/durabase over this?

3. Assuming I go for electric what would be the best method? i.e. insulation board then UFH then Ditra or vice versa? Also what adhesives are recommended?

4. I have purchased BAL flexi tile adhesive for the tiles - is this suitable for ditra/surbase mat?

Sorry for all the questions but the builder seems a bit clueless and just wants to finish the job quickly and is relying on me to tell him what I want so I'm having to learn very fast!

Thanks in advance all.

M

Where abouts in London are you, i can come and have a look and give you a quote if you like or i am sure somebody else on here local to you will do the same......... if your builder is clueless then for christ sake don't let him carry out the work, you are asking for problems.

Type Sparkles bathroom into our search box and read..... Don't make the same mistake

 

[TJ Smiler]

PS; There is a difference between work looking good and work being good.

 

[Uheat - Keith]

Agree with others here.
Insulated Construction boards, Electric Under Floor Heating, a powdered flexible self-leveling compound to cover the underfloor heating and fix the floor finish.

Warm regards.

 

[mog]

Cheers guys.