Finished floor or plaster walls, which first?

BarneyMc

Is there any clear advantage of putting in finished floors before plastering the walls or vice versa? The walls are not being 'dry lined' with any insulated slabs, just plastered.

hexosan

I've plastered the walls first. Then I'll install UFH pipes and liquid screed. Less chance of the pipes getting damaged.
Your plasterers will dislike you for this as it make it awkward moving the slab lifter on the uneven Hollowcore when their doing the ceilings.

BarneyMc

hexosan wrote: »

I've plastered the walls first. Then I'll install UFH pipes and liquid screed. Less chance of the pipes getting damaged.
Your plasterers will dislike you for this as it make it awkward moving the slab lifter on the uneven Hollowcore when their doing the ceilings.

So the plaster goes on the wall and all the way down to the slab and the perimeter insulation then against this.

If you had of put in the floor first why would there be more chance of the pipes being damaged - surely the liquid screed would protect them?

Any reason for using liquid screed rather than sand/cement?

delfagio

Hi Barney,

For me I had all external walls insulated board and internal walls plasterboard and skim coated. I had this stage done before I done my floor insulation, UFH pipes and liquid screed. My screed is almost 3 weeks in now and looking great.

If I was you, then I would plaster first 100% and then do insulation, UFH pipes and screed for these main reasons:

1.) Plastering is messy work as we all know. Show me a clean plasterer???? They are always destroyed head to toe. If you have your floors done first you will end up having your lovely smooth level floor destroyed in splashes of plaster, hard lumps of scratch coat or skim that you will then have to scrap off the lovely floor and could end up damaging the screed floor in the process scrapping off.

2.) Plastering is a wet trade. It's important not to add any moisture to the liquid screed floor after its poured during its curing and drying process, as this can effect the drying time, so if you have the floor done first and then start plastering you will have water going every where onto the screed floor as plasters usually wet down walls, use water to mix skim coats in buckets, wetting brushes to brush the skim coat etc. Trust me you will have water getting onto the screed.

3.) Most liquid screeds are a calcium sulphate screed which can sometimes have a reaction to cement based products. Hence why you must ensure your screed is acrylic primed before tiling so that the cement based grouts and tiles do not react chemically with the screed. Plastering is all cement based so just to be on the safe side you wouldn't want to risk any wet plaster or skim coat lying on the finished screed which could possibly damage it.

4.) Liquid screed is dear enough putting it in the first time around so better not have to redo, or repair in places. I'm not saying all the above would damage or destroy your screed but I wouldn't like to take the risk if it were me.

5.) As the liquid screed is a finished floor, it should really be one of the last things to go in before all 2nd fixes and finishes go in.

Let us know what you decide to do in the end.

Hope this helps

delfagio

Sorry apologies Barney just 're read the thread and I assumed your were using Liquid screed.

But if your using Sand and Cement screed then scrapping off plaster will still scrap and damage the screed, maybe even more so than a liquid screed.

hexosan

Delfagio covers most of the reasons above.
I'm going with liquid screed and I'm tight on my FFL

BarneyMc

hexosan wrote: »

Delfagio covers most of the reasons above.
I'm going with liquid screed and I'm tight on my FFL

Would you not go with sand/cement in the GF?

hexosan

BarneyMc wrote: »

Would you not go with sand/cement in the GF?

Only have 50mm to spare in the floor otherwise it'd effect my door thresholds and stairs hence the liquid screed.

F. Bohan

Hi Barney,

Wrote up this in-depth reply when I saw someone was taking the piss at you, but Internet went down and was unfortunately not able to post it. Posting it now, as it may still be of use to you, or others:

From a purely technical point of view, it is better to first place a leveled screed and only then, after the subfloor has sufficiently dried, to plaster. After all, cement is much better resistant against moisture than plaster. If plaster is exposed to moisture (or moist air) for a long duration, this may lead to the formation of mold on the plaster, weathering of the plastered surface or, in extreme cases, degradation of the plaster layer.


In practice, however, plastering is done first and flooring second. The plasterer plasters the walls from an agreed level above the concrete slab. This level needs to be specified by the client, taking into account the floor build up (fill layers, insulation, screed and floor finishing). In the absence of an agreed level, the plaster is applied from about 10 cm above the supporting floor and placed above any water barrier membranes, preventing moisture from pulling into the plaster.
After plastering, the plaster should be allowed to dry before proceeding with the flooring. Ideally, it is allowed to dry to complete dryness (meaning that, in the case of a gypsum plaster, its residual moisture content should be less than 1%). The drying time depends on many factors, such as temperature, ventilation, the layer thickness of the plaster, the suction of the substrate, its moisture content, air humidity, etc. As an indication, a plaster with a thickness of approximately 10 mm, placed on a dry surface, in a well heated and ventilated home, may already be sufficiently dry after 3 or 4 weeks. A more typical waiting time in the construction industry, however, is two weeks.
Complete dryness is of particular importance if one wants to apply paint or tile to the plaster. If not completely dry, there is a risk of damaging the plaster. Before tiling, the surface should be treated with a suitable primer. In kitchen and bathroom, a standard primer can be used. In the shower area, make sure to use a fully waterproof primer (e.g. a bitumen primer).
If the above ventilation guidelines are taken into account, there should be no issue following this sequence.


This approach has advantages with regards to:


- Spillage: no matter how careful the application, some plaster will always be spilled, and it is better to spill onto a concrete slab than onto a leveled screed or finished floor.
- Finish: it is much easier to plaster to the desired level and ensure a nice, straight finish at the bottom by putting in a leveled screed and finished floor afterwards, than doing it the other way around.


If there is a need to put in a leveled screed prior to plastering (e.g. there are a lot of pipes running across the floor, and one would like to cover these for safety reasons, or the intention is to put in wooden floors later on and additional time is required for the subfloor to dry), then it should be covered with cardboard (not plastic, as it would become quite slippery otherwise).

BarneyMc

Wow, thanks F. Bohan, not bad for a first post! This gives me great knowledge and will help me not get hoodwinked when speaking with the builder and other trades. RESPECT!

delfagio

F. Bohan wrote:

Wrote up this in-depth reply when I saw someone was taking the piss at you, but Internet went down and was unfortunately not able to post it. Posting it now, as it may still be of use to you, or others:

Who was taking the piss???

F. Bohan

delfagio wrote: »

Who was taking the piss???

There was a less than constructive first comment geared towards self-builders, and a number of comments after that stated such a reply was not helpful. I do not know what happened after that, as my Internet went down before I could add my post, but the next day those posts were gone, and there were a number of helpful ones (yours being the most expansive one) instead. I can only assume one of the moderators decided to clean up the thread at a certain point.

galwaytt

..as Delfagio says ^^^^, but also: from a practical perspective, a plasterer once told me that if the floors are in first, then it is not as easy to finish down cleanly & evenly with the trowel against the floor. Also, on the upstroke from the floor there is a tendency for the trowel to draw dust up off the screed into/onto the plaster, making the bottom few inches hard to float to a smooth finish.

Seems logical enough, but not being a plasterer myself, I can only assume.

BarneyMc

F. Bohan wrote: »

In practice, however, plastering is done first and flooring second. The plasterer plasters the walls from an agreed level above the concrete slab. This level needs to be specified by the client, taking into account the floor build up (fill layers, insulation, screed and floor finishing). In the absence of an agreed level, the plaster is applied from about 10 cm above the supporting floor and placed above any water barrier membranes, preventing moisture from pulling into the plaster.

So am I right in saying that the plaster line should finish at the finished floor, e.g. tile, wooden floor level and the perimeter insulation should fit neatly under this?

How then is the airtight layer maintained especially if the plaster finishes 10cm (should this be mm?) above the supporting floor?

homeguru

Plaster walls first its handier and less mess to clean

cork2

Anybody got any tips for cleaning spatters of liquid screed off the finished plastered walls? I just the finished the second fix carpentry in a house that had liquid screed splashed in places on the skim, it was a nightmare to scrape off and infairness the lads pumping it into the house were as careful as possible.

rampantbunny

cork2 wrote: »

Anybody got any tips for cleaning spatters of liquid screed off the finished plastered walls? I just the finished the second fix carpentry in a house that had liquid screed splashed in places on the skim, it was a nightmare to scrape off and infairness the lads pumping it into the house were as careful as possible.

Would a rub of sandpaper be the best thing? Knowing myself, if I was to go scraping it off I'd end up gouging the plaster.

The lesson I'd take from this (will be pumping at some point) is to run the plastic that goes over the floor insulation a good bit up the walls.
How high were the splash marks?

cork2

rampantbunny wrote: »

Would a rub of sandpaper be the best thing? Knowing myself, if I was to go scraping it off I'd end up gouging the plaster.

The lesson I'd take from this (will be pumping at some point) is to run the plastic that goes over the floor insulation a good bit up the walls.
How high were the splash marks?

Sand paper didn't budge it, it was like flint!! The painters kept at it with scrapers but it was a nightmare. In places there were spatters four and five feet off the ground. It's pure liquid so when they turn on the pump for the first gush of it the hose better be way out the floor and don't hold the hose up high of the ground or it'll splash. I know it's easy to say the lads pouring were messy but they were'nt and they tried to wipe off alot of the spatter as the finished the screed.

BarneyMc

BarneyMc wrote: »

So am I right in saying that the plaster line should finish at the finished floor, e.g. tile, wooden floor level and the perimeter insulation should fit neatly under this?

How then is the airtight layer maintained especially if the plaster finishes 10cm (should this be mm?) above the supporting floor?

The attached diagram might help explain what I'm talking about here... then again!

rampantbunny

BarneyMc wrote: »

The attached diagram might help explain what I'm talking about here... then again!

Where are you getting the figures of 10mm/10cm Barney?

FWIW: I have a line of DPC running round the external walls of my house, above the level of the slab. I'll only be able to plaster down to this DPC line, which will leave from there down open i.e. subject to air ingress. I've also been told that this DPC line is a common culprit where air leakage is concerned.

I've already gone around and applied mortar from the slab to the first block (curved it up the block). This ensures that any holes in the mortar under this first row of blocks is completely sealed (if it wasn't already).
This mortar closes the gap between slab and underside of the DPC a little. It will no doubt piss me off completely when I go to install my insulation boards tight to the wall as I'll have to chamfer the edges of the boards, but it was recommended that I do this by an AT installer and general passive house advocate.

Even if the above was not done it shouldn't matter. When the screed goes in I will apply tape from the plastered walls to the top of the screed. It is a specialist tape for the purpose of ensuring airtightness at this junction. I still have to work out the detail but I might be able to plaster over the tape on the wall, and just glue it to the floor. The alternative is gluing it after plastering is done, to both the plaster and the screed.

Not sure if any of that helps at all. But reply back and you can at least hit the 1000 post mark.

BarneyMc

rampantbunny wrote: »

Where are you getting the figures of 10mm/10cm Barney?

FWIW: I have a line of DPC running round the external walls of my house, above the level of the slab. I'll only be able to plaster down to this DPC line, which will leave from there down open i.e. subject to air ingress. I've also been told that this DPC line is a common culprit where air leakage is concerned.

I've already gone around and applied mortar from the slab to the first block (curved it up the block). This ensures that any holes in the mortar under this first row of blocks is completely sealed (if it wasn't already).
This mortar closes the gap between slab and underside of the DPC a little. It will no doubt piss me off completely when I go to install my insulation boards tight to the wall as I'll have to chamfer the edges of the boards, but it was recommended that I do this by an AT installer and general passive house advocate.

Even if the above was not done it shouldn't matter. When the screed goes in I will apply tape from the plastered walls to the top of the screed. It is a specialist tape for the purpose of ensuring airtightness at this junction. I still have to work out the detail but I might be able to plaster over the tape on the wall, and just glue it to the floor. The alternative is gluing it after plastering is done, to both the plaster and the screed.

Not sure if any of that helps at all. But reply back and you can at least hit the 1000 post mark.

Thanks RB. I think I'm with you now. I've setup a site meeting with my friend who is also an expert at all this. I'll grab a few photos and proposed solution.

Didn't realise I was at the 1K mark for posts... is there some sort of prize?

BarneyMc

rampantbunny wrote: »

When the screed goes in I will apply tape from the plastered walls to the top of the screed. It is a specialist tape for the purpose of ensuring airtightness at this junction. I still have to work out the detail but I might be able to plaster over the tape on the wall, and just glue it to the floor. The alternative is gluing it after plastering is done, to both the plaster and the screed.

My airtightness guy is coming back tomorrow or the day after to do any last fixes (had my prelim air tightness test the other week) before plastering begins in a few weeks time.

I think he is steering me to the method described by RB above, i.e. tape the wall floor junction after the screed has gone in.

However, my airtightness advisor has suggested applying a 6 inch tape to cover the wall dpc level (half above and half below). The plasterer will then plaster down over the top part. The radon barrier will then be laid and glued to this tape also. So this 6 inch tape would be covered on the top portion by the wall plaster and by the bottom half by the radon barrier.

For me this sounds like the most secure option but the other (applying the tape at the end) seems like the most straight forward and I suppose should be fool proof also.

What's the opinion out there?

rampantbunny

BarneyMc wrote: »

... The radon barrier will then be laid and glued to this tape also. So this 6 inch tape would be covered on the top portion by the wall plaster and by the bottom half by the radon barrier.

Your radon barrier? Is this not supposed to be under your slab, and the radon sump also?
Are you sure it is not the DPM Barney?

BarneyMc

rampantbunny wrote: »

Your radon barrier? Is this not supposed to be under your slab, and the radon sump also?
Are you sure it is not the DPM Barney?

Don't think so RB, I had to use slabs on my GF floor. Anyway it's fine as my new builder and architect are ok with it.

rampantbunny

What method did you settle on Barney for sealing the wall to floor junction?

BarneyMc

rampantbunny wrote: »

What method did you settle on Barney for sealing the wall to floor junction?

Just going to plaster walls, put in floors and then tape the wall-floor joint. This is what my air-tightness man is suggesting.

ht9zni1gs28crp

I would have thought you need to tape the bottom of the wall to the top of the insulation board, ie under the final screed? So before the screed goes in? Your screed then is you air tight line continuity...

BarneyMc

miller_63 wrote: »

I would have thought you need to tape the bottom of the wall to the top of the insulation board, ie under the final screed? So before the screed goes in? Your screed then is you air tight line continuity...

Not sure the tape would fix well enough to the insulation board or polythene cover that sits over the insulation boards? Would the tape go over the perimeter insulation or the floor insulation? Also if you did this then the tape is your airtight layer and not necessarily your screed?

e.r

What are you floor finishes as liquid screeds need to dry to .5% moisture and unless you have a commissioned UFH system it could be the summer before you install your flooring finishes

hexosan

e.r wrote: »

What are you floor finishes as liquid screeds need to dry to .5% moisture and unless you have a commissioned UFH system it could be the summer before you install your flooring finishes

Apart from turning on the UFH is there anything else that will dry out a liquid screed.

delfagio

hexosan wrote:

Apart from turning on the UFH is there anything else that will dry out a liquid screed.

The drying time takes usually 1 day per 1mm of screed up to about 45mm I think and 2days per 1mm over 45mm.

That's with the air temperature in the air been at approximately 20degrees.

So it will dry naturally in normal air temperature but if you could get your heating on after 7 days that's ideal and gradually bring it up over 3-4 week's to normal working temperature.

I let my screed dry naturally for 9 weeks and then done 3 weeks of heating before doing tiles. Moisture test carried out averaged at 0.3%

One thing to not is that you must bring it up to full working temperature gradually by 1 degree or so and then reduce it down gradually by 1 degree or so so that it does a full heat cycle. This will allow the screed to have expanded and contracted so that if it has to crack slightly it can. This must be done before laying tiles otherwise the tiles could crack.

BarneyMc

delfagio wrote: »

One thing to not is that you must bring it up to full working temperature gradually by 1 degree or so and then reduce it down gradually by 1 degree or so so that it does a full heat cycle. This will allow the screed to have expanded and contracted so that if it has to crack slightly it can. This must be done before laying tiles otherwise the tiles could crack.

For laminate floors does it matter much if the screed is not fully dry?

e.r

BarneyMc wrote: »

For laminate floors does it matter much if the screed is not fully dry?

You'd have to ask the supplier, as you cannot put on a liquid DPM as the moisture cannot escape and breaks down the screed over time.
I'm not sure if you can cover it with polythene so the moisture will not effect the laminate

delfagio

BarneyMc wrote:

For laminate floors does it matter much if the screed is not fully dry?

Again you should wait until the moisture is gone out of the screed.

You don't want to trap moisture under the laminate flooring. Usually the underlay for laminate, especially with UFH, has a moisture barrier in the underlay.

So you really don't want to rush laying flooring and risk trapping moisture under the laminate flooring and underlay

BarneyMc

delfagio wrote: »

Again you should wait until the moisture is gone out of the screed.

You don't want to trap moisture under the laminate flooring. Usually the underlay for laminate, especially with UFH, has a moisture barrier in the underlay.

So you really don't want to rush laying flooring and risk trapping moisture under the laminate flooring and underlay

What practically can be done around the house during this period? Maybe it's a time to tramp round the shops to choose tiles, laminates and just about everything else to go into the house?

hexosan

Can skirting and door frames be hung or should the floors be dry first.

delfagio

BarneyMc wrote:

What practically can be done around the house during this period? Maybe it's a time to tramp round the shops to choose tiles, laminates and just about everything else to go into the house?

We done the ground works out side and drainage, kerbing and stoned up driveway while we where waiting. We also waited about 4 weeks and then started painting, I had our 2nd fix electric been done also.

Oh and lots of shopping around for tiles and laminate, toilets, etc.

hexosan wrote:

Can skirting and door frames be hung or should the floors be dry first.

I am not 100% on this one. I had mixed reviews from carpenter's and builders who said not to do any wood work as the moisture could cause warping of frames and skirting so we held off.

I'm getting door frames and skirting and architrave been fitted this Thursday and Friday coming yay