Sand/cement or liquid screed for floor

ssloan · 06-09-2014 05:09PM #1

Going with UFH in house and trying to decide between sand/cement for floor or liquid screed for the floors? Does anyone have opinions and approx. extra cost of the liquid screed? Is the advantage if liquid screed only in the initial heat up with with UFH?

glashanator · 07-09-2014 09:16AM

ssloan wrote: »

Going with UFH in house and trying to decide between sand/cement for floor or liquid screed for the floors? Does anyone have opinions and approx. extra cost of the liquid screed? Is the advantage if liquid screed only in the initial heat up with with UFH?

Depends what you're looking for. If you both are out all day and home late, then you might want a faster shorter heat up time, liquid screed might suit.

If home all day ,definitely sand and cement.

Best way to think of underfloor heating is like a storage heater, heats up and releases heat all day. thats why the vast majority go with sand cement screed.

Any new builds well insulated and airtight houses now adays are moving away from the heat up fast cool down fast method of heating. Its all about getting heat into the house slowly , then keeping there, topping it up slightly as the temp drops slightly, more efficient and comfortable way to run your home. And again, this is why sand and cement screed is used.

Liquid screed can be up to 50% more expensive in areas, probably more.

declan52 · 07-09-2014 07:07PM

For mine the cost difference was 650 for 140sqm of floor. I went for sand cement as you can have issues with getting tiles to bond to the top of the liquid screed if its not sanded down and sealed correctly.

BarneyMc · 08-09-2014 11:31AM

I am looking at these 2 options also. I will have UFH in a 2800 sq feet house and using a air to water HP as the main source of heat. I'll also be lighting a solid fuel stove and I work from home.

This would tend to lean towards the sand/cement option and use the cheaper night rate electricty. However, I would like to install PV cells in the future and this would work better, I think, with a more responsive heating system, i.e. liquid screed.

It's a hard one to call!!!!

RITwing · 08-09-2014 11:38AM

Opinion only.

The desirbility of seeking fast reponse from UFH comes from our culture of badly built houses. We are used to coming in from the cold to a badly insulated and drafty house and like to boiler to work like buggery to give us hot rads and a warm house in minutes.

But building to current regulations will require high levels of insulation , air tightness and a properly designed and installed ventilation system.
So the manner in which the houses is heated is by a slow constant trickle.

Thin screeds and fast response do not offer any advantage then.

BarneyMc · 08-09-2014 11:42AM

If I'm lighting a stove every day then maybe I'd want the heating system (heat pump) to adjust accordingly and not 8 hours later?

RITwing · 08-09-2014 11:47AM

If you build to b reg standards you should find that you are in fact not needing to light the stove every day. Once the house is warmed up initilally over 3-4 weeks then the HP will be fine save for the most bitter winter days.

BarneyMc · 08-09-2014 12:20PM

Pumping 250mm cavity, HRV, high levels of insulation, etc. My walls will be a good heat 'sink'.

I hope to heat the stove as needed and as I work from home it will not be a bother to light and keep going. For the days that I don't bother to light it or on very cold snaps would it not be better to have the HP respond quickly as needed?

Also if going the PV cell route sometime in the future, if there's an 8 hour delay for the heat to be released from a sand/cement floor then it will only be released late and not during the day when I need it (I work from home)?

DeeJunFan · 10-09-2014 01:11PM

BarneyMc wrote: »

Pumping 250mm cavity, HRV, high levels of insulation, etc. My walls will be a good heat 'sink'.

I hope to heat the stove as needed and as I work from home it will not be a bother to light and keep going. For the days that I don't bother to light it or on very cold snaps would it not be better to have the HP respond quickly as needed?

Also if going the PV cell route sometime in the future, if there's an 8 hour delay for the heat to be released from a sand/cement floor then it will only be released late and not during the day when I need it (I work from home)?

Suppose it depends Barney.

If you are keeping your slab at a constant temp to keep the house comfortable with your levels of insulation and good air-tightness i doubt you will have a situation where you are going to be looking for immediate response from the slab. More likely you will be living in comfortable conditions 95% of the year with your UFH and only lighting the stove on really cold days.

Do you know how much heat you need in your house to get it up to temp?

I have been in a well insulated and fairly air-tight. (not as air tight as people aim now) and when the stove is lit its generally put out within a hour or two as it over heats the space.

BarneyMc · 10-09-2014 04:52PM

DeeJunFan wrote: »

Suppose it depends Barney.

If you are keeping your slab at a constant temp to keep the house comfortable with your levels of insulation and good air-tightness i doubt you will have a situation where you are going to be looking for immediate response from the slab. More likely you will be living in comfortable conditions 95% of the year with your UFH and only lighting the stove on really cold days.

Do you know how much heat you need in your house to get it up to temp?

I have been in a well insulated and fairly air-tight. (not as air tight as people aim now) and when the stove is lit its generally put out within a hour or two as it over heats the space.

Will dig out the heat requirement later and post.

The house where the stove over heats the house sounds like one where the walls are dry lined?

BarneyMc · 12-09-2014 06:01AM

The big advantage I see with going the sand/cement route is to 'charge' the slab at night rate electricity.

In a very well insulated house that is not dry lined and where a stove will be lit daily (as needed) then surely the demand on the HP would be minimal. Therefore would it not be better for the HP to come on for a short period during the day (warmer temps) when and if required and have the heat in 1-2 hours? There is a higher monthly rental for the night rate meter I believe so this could be saved also (just run the HP during the day).

Another factor is the possibility of using PV cells to power the HP. As this could only happen during daylight hours it would be good to have the heat appear in the house within 2 hours rather than 8 hours?

BarneyMc · 12-01-2015 09:25PM

Can anyone else out there share their experience/thoughts of which floor type to go for? Is it possible to have a 3 inch sand/cement floor?

declan52 · 13-01-2015 08:02AM

BarneyMc wrote: »

Can anyone else out there share their experience/thoughts of which floor type to go for? Is it possible to have a 3 inch sand/cement floor?

I have just 70mm of sand cement on mine. It got mixed with fibres to strengthen it. It is down near 4 months and on the bits not covered by flooring there are no cracks. I also added mapie 704 to increase the drying out time. Floor was dry after 21 days.
Takes about 2 hrs to heat up with ufh and stays warm for 5-6 hrs. How long it stays warm will depend on how well insulated and airtight your house is.

BarneyMc · 13-01-2015 08:05AM

declan52 wrote: »

I have just 70mm of sand cement on mine. It got mixed with fibres to strengthen it. It is down near 4 months and on the bits not covered by flooring there are no cracks. I also added mapie 704 to increase the drying out time. Floor was dry after 21 days.
Takes about 2 hrs to heat up with ufh and stays warm for 5-6 hrs. How long it stays warm will depend on how well insulated and airtight your house is.

What are the fibres called?

declan52 · 13-01-2015 08:09AM

Not sure what their technical name is the screed guys brought them. They look like a plastic rope that has been shredded. About 50mm long width of hair type thing. Whoever is doing your floor will know about them.

Hollywood130 · 13-01-2015 02:56PM

I'm looking at floor screeds myself now, not putting in UFH, and not sure whether to go sand/cement or self-levelling floor screed. For supply only from a local company, sand/cement is €100 per meter and the self-levelling is €172. Tilers have said self-levelling is better as they won't have to use any bonder. But the company I rang for a quote said I should only need sand/cement because I'm not putting down underfloor heating... help please...

declan52 · 13-01-2015 03:30PM

You are better of going for sand cement if you have no ufh. The flo screeds all need sanded and sealed and if you are tiling you def need this done or your tiles won't stick to the floor. No matter what screed you will pick you will have to use some sort of bonding solution to help the adhesive stick to the floor.

Hollywood130 · 13-01-2015 03:43PM

Ok, is 80mm ok to go for in sand/cement? That takes the floor level with our front door. The plans say 50mm but that would barely cover the plumbers pipes and it won't bring the floor level with the doors. I was told we could go as high as we wanted, 80mm is definitely sufficient though

declan52 · 13-01-2015 03:46PM

Have you any insulation on the floor.

Hollywood130 · 13-01-2015 03:49PM

Yes the insullation went in with the sub-floor

declan52 · 13-01-2015 03:54PM

OK. 80mm screed will do but you only have 30mm coverage over the pipes. Not much and you might get cracks at these points.

Hollywood130 · 13-01-2015 04:07PM

declan52 wrote: »

OK. 80mm screed will do but you only have 30mm coverage over the pipes. Not much and you might get cracks at these points.

Would you recommend more screed?

declan52 · 13-01-2015 08:58PM

Are you putting the screed down yourself. Sounds like it. The depth of the screed is determined by your door head heights. Can't put 80mm down if there will be 50mm of a gap under the door when its hung or you wouldn't want to be cutting 25mm of the bottom of a door if you put to much in.

Hollywood130 · 13-01-2015 09:10PM

declan52 wrote: »

Are you putting the screed down yourself. Sounds like it. The depth of the screed is determined by your door head heights. Can't put 80mm down if there will be 50mm of a gap under the door when its hung or you wouldn't want to be cutting 25mm of the bottom of a door if you put to much in.

We bought the house at builders finished basically, the plans say 50mm but when you measure to the door theres 80mm room for screed, 50mm wouldn't bring the floor to the door heights, with 80mm its even with the door. No we'll have someone put it down, we wont be doing it ourselves. Just pricing around at the moment, not too many in my area doing

declan52 · 13-01-2015 09:38PM

Measure from the inside of your internal door frames. You need min of 2m to allow for a standard door height and that will give you enough for a 10mm tile. If you are going for a solid floor then you need a bit more.

Hollywood130 · 13-01-2015 10:38PM

declan52 wrote: »

Measure from the inside of your internal door frames. You need min of 2m to allow for a standard door height and that will give you enough for a 10mm tile. If you are going for a solid floor then you need a bit more.

Thats great, thank you so much for your help

delfagio · 15-01-2015 12:00PM

Hi Hollywood130,

Just seen this thread and said I would jump in really quick. You mention that you are going to put down 80mm sand/cement screed and that this would bring you level with the door (exterior front door I assume), just make sure you remember to take into account the depth of floor finishes so that your front door, side door, back door can still open. Floor tiles can be approx. 10mm thick and you may need possibly 3-5mm bed of adhesive, even solid wooden floor can be almost 18mm thick.

No point putting screeded floor in exactly level with front door only to find you only have 5-10mm clearance from the bottom of the door to the top of the screeded sand/cement floor because you would not have enough room to lay your floor finishes and still be able to open the door.

Maybe you have considered this, but just thought I would mention it, as I almost got caught with that myself.

Hollywood130 · 15-01-2015 12:46PM

Initially I hadn't considered this but then looked at the sample tiles and thought 'Oh ya'!!! With 80mm there is still space for floors though. We have a guy calling tomorrow to have a look and give at price on laying the screed so we'll see what he has to say.

delfagio · 15-01-2015 01:25PM

Brilliant, good on ya

, hope all goes well with the screed and finished floors, I'm just in the process of getting ready for laying my own insulation, underfloor heating pipes downstairs & upstairs and then hopefully pouring the screed before end of this month. :eek:

Hollywood130 · 15-01-2015 03:15PM

You too, it's a stressful process, very hard to keep an eye on everything when you're working full time. Wow before the end of this month?? Our plasterer is starting 24th of this month so it will probably be mid-February before I get laying screed. Are you pouring screed before plastering?

delfagio · 15-01-2015 03:26PM

Hey Hollywood130,

No I have all the internal plastering finished.

We went with a timber frame SIP panel construction, so all our internal walls just need to have plasterboard/insulated plasterboard fixed to them and then skim coated.

Be prepared though.....plastering is a messy trade. We were keeping the house clean on a weekly basis which was working fine......then the plasterers came to do their work and the place turned into a bomb site, dust from plaster boards, screws everywhere, off cuts of plasterboards everywhere, skim coat on floors, windows, just a mess, was glad to see the end of the plastering stage ha ha

Yea its tough keeping up with it all and working full time as well, lots of late nights, early mornings & late nights at weekends, we should be in all going well for mid March, paddy's week sometime

Sand/cement or liquid screed for floor

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