Floor Screed Recommendations

Rushy Fields

Looking for advice on floor screed types.
I have 150mm insulation on ground floor and 50mm insulation on first floor. I am putting down underfloor heating in both ground and first floors. My geat source is Geothermal Hoizontal collector type.
I am just wondering wich is the best type screed to use for this type of heating.
Floor coverings will be engineered timber and tiles.

Sand & Cement? Heard it is good for retaining the heat?
Liquid Cement based screed?
Calcium based screed?
OR
Anhydrite Screed? Good for letting out heat quickly?

I have 38mm insulated slabs on walls and 150mm pumped cavity. And Airtightness membrane and tape installed.
I dont think the gouse willbe cold so i am just looking for an all rounder screed.
Any advice is welcome.

self_builder

With 150mm insulation how much room is left for insulation? Afaik you will need a deeper screed if it is sand & cement

sydthebeat

self_builder wrote: »

With 150mm insulation how much room is left for insulation? Afaik you will need a deeper screed if it is sand & cement

Still asleep methinks

Sligoronan

I have used cement base screeds for years. But 2 years ago I started useing a hemihydrate calcium sulphate screed. Works out about €2 a square meter more expensive but by far a superior job. It goes in at 50mm and is light weight as well. I believe it works far better for underfloor heat. Here is a link for it.http://www.harringtonconcrete.ie/products-details.php?pid=157
Pm me if u want to see it as I had a house poured with it last week.

Tifosi

nealger wrote: »

Looking for advice on floor screed types.
.

Sand & Cement? Heard it is good for retaining the heat?
Liquid Cement based screed?
Calcium based screed?
OR
Anhydrite Screed? Good for letting out heat quickly?

.
I dont think the gouse willbe cold so i am just looking for an all rounder screed.
Any advice is welcome.

Normally a sand cement finish is sufficient, the key is to retain the heat once the screed has heated up. worth asking your underfloor installer what they recommend. You have a 100mm floor build up on the upper floor, what flooring system are you proposing.

Rushy Fields

Tifosi wrote: »

Normally a sand cement finish is sufficient, the key is to retain the heat once the screed has heated up. worth asking your underfloor installer what they recommend. You have a 100mm floor build up on the upper floor, what flooring system are you proposing.

I am using underfloor heating from Geothermal. I dont think i should be retaining the heat. I want the heat to emit into the rooms, thats why i was veering towards the thinner screeds.
I heard the sand and cement screeds are thicker and retain the heat. Maybe im wrong!. Thats why i am here asking the questions, looking for answers.
I have 60 to 70mm for the screed. It means that if i go lower on the groun floor i will have to use a thicker tile or timber flooring.
I have 50 to 65mm depth upstairs.

Sligoronan

nealger wrote: »

I am using underfloor heating from Geothermal. I dont think i should be retaining the heat. I want the heat to emit into the rooms, thats why i was veering towards the thinner screeds.
I heard the sand and cement screeds are thicker and retain the heat. Maybe im wrong!. Thats why i am here asking the questions, looking for answers.
I have 60 to 70mm for the screed. It means that if i go lower on the groun floor i will have to use a thicker tile or timber flooring.
I have 50 to 65mm depth upstairs.

hemihydrate calcium sulphate is your answer.

Rushy Fields

Sligoronan wrote: »

hemihydrate calcium sulphate is your answer.

How much for a 255sqm two storey house?
Is it priced per job, per sqm, or per cubic mtr?

Sligoronan

It is priced by the sq meter at 50mm thick. I paid 4600 for 260sq at 50mm thick. Took a little crying to get him down to that. Works out at €18 per sq meter.

AnarchistKen

I would avoid hemihydrate if you need a quick drying time. As it goes in fully liquid it's just going to take longer to dry. I've heard horror stories about having to use expensive DPM products so floor finishes can be laid

A sand and cement semi dry screed will be a faster drying screed. It's goes in at a low moisture content and one crew would knock out over 250m2 a day.

Sligoronan

AnarchistKen wrote: »

I would avoid hemihydrate if you need a quick drying time. As it goes in fully liquid it's just going to take longer to dry. I've heard horror stories about having to use expensive DPM products so floor finishes can be laid

A sand and cement semi dry screed will be a faster drying screed. It's goes in at a low moisture content and one crew would knock out over 250m2 a day.

Why would u be using a expensive DPM on top of insulation that has hundreds of penetrations from the clips of the under floor heat.
My grief with sand and cement screed is the cracking that comes when the heat goes on.

sydthebeat

Sligoronan wrote: »

Why would u be using a expensive DPM on top of insulation that has hundreds of penetrations from the clips of the under floor heat.
My grief with sand and cement screed is the cracking that comes when the heat goes on.

i think s/he meant that, because the floor was slow drying, a DPM was placed OVER the floor screed before the floor finish was installed.

This wouldnt be affected by the UFH.

highdef

Sligoronan wrote: »

hemihydrate calcium sulphate is your answer.

Agreed, I used this place and have been very happy. Got a good price too. Can't remember how much I paid but it was not nearly as bad as I thought it would be - http://www.fastfloorscreed.ie/

tootsy70

Sligoronan wrote: »

My grief with sand and cement screed is the cracking that comes when the heat goes on.

Any cracks ive seen in sand and cement screed dont really cause any problems. Once the other layer of floor goes on ie-carpet,wooden floor,tiles etc.. then the cracks dont get seen so no need to worry about them IMO

AnarchistKen

tootsy70 wrote: »

Any cracks ive seen in sand and cement screed dont really cause any problems. Once the other layer of floor goes on ie-carpet,wooden floor,tiles etc.. then the cracks dont get seen so no need to worry about them IMO

I've always been advised to carry these joints through the screed and into the finish for example a PVC expansion strip in vinyl. OP mentioned timber flooring so should be fine

Rushy Fields

AnarchistKen wrote: »

I would avoid hemihydrate if you need a quick drying time. As it goes in fully liquid it's just going to take longer to dry. I've heard horror stories about having to use expensive DPM products so floor finishes can be laid

A sand and cement semi dry screed will be a faster drying screed. It's goes in at a low moisture content and one crew would knock out over 250m2 a day.

Im not stuck for time but from a curiosity point of view, how long does it take for the screed to dry out if using the hemi hydrate screed?
Anyone hear of a screed called "cement based fast dry geo floor"?
Sounds like a made up name!

Sligoronan

Hydrate dryes in 3 days to be able to work on it. When I use it I usually turn the underfloor heat onto floor drying mode after a week and it is dryed out after about 2 more weeks.

AnarchistKen

nealger wrote: »

Im not stuck for time but from a curiosity point of view, how long does it take for the screed to dry out if using the hemi hydrate screed?
Anyone hear of a screed called "cement based fast dry geo floor"?
Sounds like a made up name!

Depends on the climatic conditions at the time of pouring. With weather like this you wouldn't be waiting too long say two weeks to reach <5% MC. However throw your mind back to March with the cold spell you could have waited over 8 weeks to reach 5% MC

Oisinmurff

I used a pumped self levelling screed last year on geo thermal my ground floor 65mm screed and same on first floor heating working very good it was a cement base with 6mm lime stone chip which my underfloor heating company wanted to use as they said it was better for the geo thermal so I went with what he asked for!!
Climate control were underfloor contractors and screed was done by a company from ballinrobe was very happy with them they also fitted our insulation prior to underfloor company which saved us time and money a lot cheaper than local hardware as they told me they buy direct from kingspan

zrejvpx

nealger wrote: »

I am using underfloor heating from Geothermal. I dont think i should be retaining the heat. I want the heat to emit into the rooms, thats why i was veering towards the thinner screeds.

With GSHP I think you'd want to run the pump at night (cheaper electricity) and then let the heat slowly release from the thermal mass in the floor over the day so a thinner screed mightn't be best. If you're away all day, then maybe you'd want a quicker response time in the evening but then I'd think you'll be running the pump on the higher electricity rate.

(I put in 100mm sand and cement)

Waters10

Oisinmurff wrote: »

I used a pumped self levelling screed last year on geo thermal my ground floor 65mm screed and same on first floor heating working very good it was a cement base with 6mm lime stone chip which my underfloor heating company wanted to use as they said it was better for the geo thermal so I went with what he asked for!!
Climate control were underfloor contractors and screed was done by a company from ballinrobe was very happy with them they also fitted our insulation prior to underfloor company which saved us time and money a lot cheaper than local hardware as they told me they buy direct from kingspan

Would appreciate if you could PM me details of screed company from Ballinrobe as I'm at that stage of build
Using geothermal UFH with HVRS and air tightness first phase test of 0.8 ac/hr.

Currently looking at screed suppliers;
1. Fast floor screed- Alpha hemi hydrate screed @ 50mm depth. Like all the pros with fast drying and levelling
2. Sand and Cement based.

Floor levels speced by engineer are ;
Ground Floor = 150mm thick (75mm insulation + 75mm screed)

First Floor = 75mm thick (25mm insulation + 50mm screed)

Concerned with sand and cement finish .i.e cracks, dust, labour intensive damage to doors etc.
Any suggestions welcome
Thanks

AntrimGlens

Our ufh pipes went in yesterday and speaking with the plumber last night he asked what sort of floor i am putting in. Its 100mm sand cement on ground floor over 150mm kingspan insulation and on first floor 75mm sand cement screed over 75mm insualtion. He says to use a 10mm chip in the screed as it will retain the heat much longer, which is obviously a benefit but obviously its going to cost more to buy and to get laid as it will be harder to pump and to screed.
Anyone used it previously and would it really have the added benefits over same thickness sand cement screed??

Waters10

Oisinmurff wrote: »

I used a pumped self levelling screed last year on geo thermal my ground floor 65mm screed and same on first floor heating working very good it was a cement base with 6mm lime stone chip which my underfloor heating company wanted to use as they said it was better for the geo thermal so I went with what he asked for!!
Climate control were underfloor contractors and screed was done by a company from ballinrobe was very happy with them they also fitted our insulation prior to underfloor company which saved us time and money a lot cheaper than local hardware as they told me they buy direct from kingspan

Would appreciate if you could PM me details of screed company from Ballinrobe as I'm at that stage of build using climate control also.Thanks

Safehands

nealger wrote: »

Looking for advice on floor screed types.
I have 150mm insulation on ground floor and 50mm insulation on first floor. I am putting down underfloor heating in both ground and first floors. My geat source is Geothermal Hoizontal collector type.
I am just wondering wich is the best type screed to use for this type of heating.
Floor coverings will be engineered timber and tiles.

Sand & Cement? Heard it is good for retaining the heat?
Liquid Cement based screed?
Calcium based screed?
OR
Anhydrite Screed? Good for letting out heat quickly?

I have 38mm insulated slabs on walls and 150mm pumped cavity. And Airtightness membrane and tape installed.
I dont think the gouse willbe cold so i am just looking for an all rounder screed.
Any advice is welcome.

I would suggest either sand/cement or Anhydrite. The sand/cement would need to be applied semi dry rather than wet. It should allow you to fit your floor finishes quicker than an Anhydrite, which takes longer to dry. You will need to make sure that you have a minimum of 35mm thickness of either screed on top of the pipes