Flooring over UFH

[PaulMJOB]

I am having underfloor heating installed. It's between joists in a weak screed mix.

I want to fix tiles in the kitchen area and engineered wood in the dining area.

Should I fix ply (what thickness?) to the kitchen and tile over. Should the ply be glued or screwed to the joists?

With the engineered board should I get a thick board (20 - 22mm) and fix directly to the joists or glue to the screed, bearing in mind it's a weak mix or should i fix ply first?

I've been given conflicting information and am totally confused. Any advice greatly appreciated.

 

[mac391]

First you need to gather lots of info about the screed. A "weak screed" = not enough info. If if's fairly recent and you can ask, the builder might have a data sheet he's worked off. If you can't ask the builder, then the heating system should have a name to it and you could contact them for the data. There's too many types of screeds to take a chance, i generally stick to what i know on screeds but i know there's someone on here (tradesperson) who is well up on all types of screeds, i'll find his name and get back to you.

Generally though your screed could be sand/cement, analhydrate, power floated, latex etc etc and they all take adhesives differetly.

The use of Ply would solve the issue for you to move on but it also raises the floor height significantly and slows wam up time down.

What would work is,,, ceramic tiles over a latex screed, using flexi tile adhesive & grout, (depending on heating screed!!) and Engineered wood floor over DPM underlay (floating floor)

I am having underfloor heating installed. It's between joists in a weak screed mix.

I want to fix tiles in the kitchen area and engineered wood in the dining area.

Should I fix ply (what thickness?) to the kitchen and tile over. Should the ply be glued or screwed to the joists?

With the engineered board should I get a thick board (20 - 22mm) and fix directly to the joists or glue to the screed, bearing in mind it's a weak mix or should i fix ply first?

I've been given conflicting information and am totally confused. Any advice greatly appreciated.

 

[mac391]

Sorry, i should have read it right, you're having it installed so just get the data sheet.

First you need to gather lots of info about the screed. A "weak screed" = not enough info. If if's fairly recent and you can ask, the builder might have a data sheet he's worked off. If you can't ask the builder, then the heating system should have a name to it and you could contact them for the data. There's too many types of screeds to take a chance, i generally stick to what i know on screeds but i know there's someone on here (tradesperson) who is well up on all types of screeds, i'll find his name and get back to you.

Generally though your screed could be sand/cement, analhydrate, power floated, latex etc etc and they all take adhesives differetly.

The use of Ply would solve the issue for you to move on but it also raises the floor height significantly and slows wam up time down.

What would work is,,, ceramic tiles over a latex screed, using flexi tile adhesive & grout, (depending on heating screed!!) and Engineered wood floor over DPM underlay (floating floor)

I am having underfloor heating installed. It's between joists in a weak screed mix.

I want to fix tiles in the kitchen area and engineered wood in the dining area.

Should I fix ply (what thickness?) to the kitchen and tile over. Should the ply be glued or screwed to the joists?

With the engineered board should I get a thick board (20 - 22mm) and fix directly to the joists or glue to the screed, bearing in mind it's a weak mix or should i fix ply first?

I've been given conflicting information and am totally confused. Any advice greatly appreciated.

 

[PaulMJOB]

The detail from the UFH company states that the screed mix is to be 8:1. It is "!pug" or "biscuit" mix between and flush with the joists. It is not structural.

 

[WoodYouLike]

Most wood-engineered manufacturers recommend that their floor should be fully bonded to the screed when there is UFH involved (to prevent air-gaps, which could play havoc with the UFH efficiency). Use flexible adhesive for this with a correct notched trowel
Or indeed secret nail load-bearing engineered boards directly onto the battens/joists - which should be high and wide enough and not further apart than 35 - 40cm. Plus every board should connect with at least 3 battens

Also important to know how to treat your UFH before, during and after installation - even if you have it professionally installed.