Hollowcore concrete sealer

hexosan

Looking at laying a liquid screed on top of my Hollowcore and the supplier has suggested sealing the Hollowcore first with a liquid sealer which is sprayed on top instead of laying down plastic sheeting and taping it back to the walls.

Has anyone come across a product like this or have a name I could look up.

Strolling Bones

I would make the screed installer resposnsible for all above slab. Prep works, UFH pipes, insulations, sealing penetrations and then screed pour.

Unless your are doing all yourself of course. In which case ask the hollowcore guy what he is talking about.

sydthebeat

the main air tightness risk factor is between the slabs and the walls... thats why the membrane should be sealed to the wall under the slab, be carried around the face of the slab and be sealed to the wall over.

thats why sealing the slabs themselves is pretty pointless

Strolling Bones

You need to contain liquid screeds otherwise they litterally go all over the place.

I assume that is the point of the OP query.

sydthebeat

Strolling Bones wrote: »

You need to contain liquid screeds otherwise they litterally go all over the place.

I assume that is the point of the OP query.

That makes more sense, my bad

hexosan

Ye went off on a tangent there alright.

Hollowcore is in and wrapped. It's the screed supplier who suggested liquid sealing the surface of the Hollowcore prior to the screed been poured.
This replaces the need to using polythene sheeting over the floor area which has to be returned up the wall and taped in place.

@strolling bones no screed supplier (I know of) installs the UFH pipes that job would be left to the plumber or your heat pump supplier.

hexosan

Ye went off on a tangent there alright.

Hollowcore is in and wrapped. It's the screed supplier who suggested liquid sealing the surface of the Hollowcore prior to the screed been poured.
This replaces the need to using polythene sheeting over the floor area which has to be returned up the wall and taped in place.

@strolling bones no screed supplier (I know of) installs the UFH pipes that job would be left to the plumber or your heat pump supplier.

hexosan

The reason polythene or a liquid sealer is used is to prevent the slab below from sucking the moisture out of the screed causing it to dry out too fast and crack.

I'm looking for info on the liquid sealer a product name or recommendation.

Strolling Bones

hexosan wrote: »

The reason polythene or a liquid sealeris used is to prevent the slab below from sucking the moisture out of the screed causing it to dry out too fast and crack.

stop the stuff from pouring out all over the place.

I would not rely on any liquid sealer application to stop all gaps.

But do keep us in the loop with this please.

Strolling Bones

hexosan wrote: »

@strolling bones no screed supplier (I know of) installs the UFH pipes that job would be left to the plumber or your heat pump supplier.

Best to keep looking. If the plumber damages the liquid screed containment be it polythene - or liquid sealer - will he take responsibility.

Let one company take on responsibility for all the processes from conc slab up to finished screed.

Seek and you shall find.

hexosan

Strolling Bones wrote: »

stop the stuff from pouring out all over the place.

I would not rely on any liquid sealer application to stop all gaps.

But do keep us in the loop with this please.

I think you'll find your wrong there because from three of the top liquid screed installer they have all stated that the reason for the polythene is to prevent the slab below drawing the moisture out of the screed causing it to dry out to quickly.
That is also the reason for the liquid sealer to seal the surface of the Hollowcore preventing it drawing in the moisture from the screed.

If the whole floor area is to be covered in screed why would I want to contain it ?

I can see where there might be some confusion here I'm applying the screed directly to the top of the Hollowcore. I can see how you assume the polythene contains the screed over PIR insulation boards as it would make it way in between the gaps in the boards causing them to lift.

Can you point me to a supplier who claims differently.

On the point of having the screed supplier do the ufH piping that's just ridiculous as when there's a problem with the heating what's the plumber going to say "that's because an outside party supplied your pipe work and I'm not going to stand over a "concrete guy" trying to do a plumbers job. And again please free feel to supply details of liquid screed suppliers who provide this service (by PM if your not allow mention them here)

Strolling Bones

I think I shall learn more from you.
Keep posting please.

hexosan

Strolling Bones wrote: »

I think I shall learn more from you.
Keep posting please.

Instead of implying your right how about this time you provide some info to back up what your saying.

As I've said the liquid screed suppliers (I assume they know their own businesses) have a stated (in my situation) that the polythene or liquid sealer is been used to prevent the Hollowcore slab drawing moisture from the screed.

The only area in my house where the screed needs to be contained is at the stairs where a board will be fixed to prevent it flowing over.

hexosan

So again back to my original post does anyone have any details about the liquid sealers.

Strolling Bones

What does your concrete guy say - it is his suggestion after all.

hexosan

Strolling Bones wrote: »

What does your concrete guy say - it is his suggestion after all.

See my original post for the answer to that question its there if your take the time to read it.

Strolling Bones

Are you containing UFH pipes in the screed without an insulation layer?

hexosan

Strolling Bones wrote: »

Are you containing UFH pipes in the screed without an insulation layer?

Yes on one floor (there's no issue with thermal bridging as the floor is thermally broken) and I already know it's not considered best practice as it increases the thermal mass of the floor which leads to a less reactive system to temp change.

BryanF

May I ask, Depth of screed minus depth of pipes =

Strolling Bones

How are the slabs jointed?

hexosan

BryanF wrote: »

May I ask, Depth of screed minus depth of pipes =

50mm screed and off the top of my head UFH pipe is 16/17mm. So 33ish mm cover

hexosan

Strolling Bones wrote: »

How are the slabs jointed?

Slabs had a cambered joint which was grouted after they were installed.

Strolling Bones

Liquid screed is VERY liquid.

Provided all slab joints are grouted well and that all wall surfaces are prefectly sealed - it might work.

But I think you are getting a bum steer about a liquid sealer.

Use polythene as seen in this clip (blue )

BarneyMc

hexosan wrote: »

Yes on one floor (there's no issue with thermal bridging as the floor is thermally broken) and I already know it's not considered best practice as it increases the thermal mass of the floor which leads to a less reactive system to temp change.

Surely just 1 inch of insulation would be a good idea?

hexosan

BarneyMc wrote: »

Surely just 1 inch of insulation would be a good idea?

It would be if I had the room to fit it in.

hexosan

Strolling Bones wrote: »

Liquid screed is VERY liquid.

Provided all slab joints are grouted well and that all wall surfaces are prefectly sealed - it might work.

But I think you are getting a bum steer about a liquid sealer.

Use polythene as seen in this clip (blue )

Correct the slabs are perfectly grouted and all the wall surfaces are perfectly sealed.
I'm surprised more than one supplier has stated exactly the same thing it would be unusual(not unknown) for two of them to be telling the same lie

It seems that if liquid screed is laid on Hollowcore without polythene or a sealer the Hollowcore will absorb moisture out of the floor. That explanation makes sense to me, it's like painting a freely plastered wall it soaks up the first cost.

Strolling Bones

Lets know what you do and how it goes.

Good luck in any event (really)

hexosan

Strolling Bones wrote: »

Lets know what you do and how it goes.

Good luck in any event (really)

Will do. Thanks.

Still need a name for the liquid sealer if anyone knows anything about it.

Safehands

hexosan wrote: »

Will do. Thanks.

Still need a name for the liquid sealer if anyone knows anything about it.

You could look up "Liquid Vapour Membrane" by Parex UK. Sounds like it might do the trick. Google it.

hexosan

For anyone looking I've found one sealer called SBR going to look into it and see will it do the job.

hexosan

Safehands wrote: »

You could look up "Liquid Vapour Membrane" by Parex UK. Sounds like it might do the trick. Google it.

Thanks for that. If it doesn't do this job I've another that it could work for.

Safehands

hexosan wrote: »

For anyone looking I've found one sealer called SBR going to look into it and see will it do the job.

Not raw SBR. Maybe a slurry with OPC though. I believe the Liquid Vapour Membrane is SBR based.

hexosan

Safehands wrote: »

Not raw SBR. Maybe a slurry with OPC though. I believe the Liquid Vapour Membrane is SBR based.

Was just talking with a rep who said I'd need to use a 2:1 water mix with the SBR

Can then be sprayed on with a napsack

Safehands

hexosan wrote: »

Was just talking with a rep who said I'd need to use a 2:1 water mix with the SBR

Can then be sprayed on with a napsack

To do what exactly?

galwaytt

hexosan wrote: »

Yes on one floor (there's no issue with thermal bridging as the floor is thermally broken) and I already know it's not considered best practice as it increases the thermal mass of the floor which leads to a less reactive system to temp change.

I know this was the subject of a thread before, and sorry for the hijack, but as it's not done yet, it's still worth restating : the purpose of insulation under the screed is not only insulation, it's to allow for differential movement of the screed relative to the deck and walls. If you do not insulate, how will you accomodate this movement (and the pipes within it remember........)

I have screed on FF, tiled, and believe me when I tell you, it will move.

The thermal issue we will agree to disagree on.

galwaytt

Strolling Bones wrote: »

Liquid screed is VERY liquid.

Provided all slab joints are grouted well and that all wall surfaces are prefectly sealed - it might work.

But I think you are getting a bum steer about a liquid sealer.

Use polythene as seen in this clip (blue )

We had to use polythene on a GF, on a FF I can't see how you'd avoid it. If nothing else, surely polythene is cheaper ?

And I know you say your floors are perfectly grouted etc, but as you say, they're also cambered. Which means your screed will be a different thickness mid-camber to edge -and that alone will promote cracking in the screed.

"not having" space for minimal insulation will be remiss if you get a lot of cracking in the screed after........

BarneyMc

Are these problems possible with sand/cement also if no insulation is laid?

galwaytt

BarneyMc wrote: »

Are these problems possible with sand/cement also if no insulation is laid?

Yes. You've (still) got a heated screed, and colder (heavier, denser) substrate - they won't expand/contract at the same rate no matter what you do.

hexosan

galwaytt wrote: »

I know this was the subject of a thread before, and sorry for the hijack, but as it's not done yet, it's still worth restating : the purpose of insulation under the screed is not only insulation, it's to allow for differential movement of the screed relative to the deck and walls. If you do not insulate, how will you accomodate this movement (and the pipes within it remember........)

I have screed on FF, tiled, and believe me when I tell you, it will move.

The thermal issue we will agree to disagree on.

I have no facility to install insulation not 5mm never mind 25mm. If I could of I would happily of installed it so its a moot point.

I'm aware of your previous posts on the slabs been thermally broken and I don't see it as an issue (for my build)

hexosan

I don't want to come across as smart or ungrateful with this next comment but I'm well aware of the pros and cons to what I'm doing. I've read a hundred threads on these issues and I don't need to be made aware or have the issues pointed out to me. (I seen them pointed out to others)

Only I'm familiar with my circumstances and I'm simply working to what I have on site, all I want from this thread is info on liquid sealers for concrete. We're three pages and 40 comments in yet only one person (safe hands) has attempted to answer my question.

Strolling Bones

hexosan wrote: »

We're three pages and 40 comments in yet only one person (safe hands) has attempted to answer my question.

Well who wants to help a drunk find his car keys....:rolleyes:

hexosan

Strolling Bones wrote: »

Well who wants to help a drunk find his car keys....:rolleyes:

Well that's the joy of the Internet if you don't want to answer your not contractually obliged too.

Strolling Bones

You have received answers.
You just don't like them.

hexosan

Strolling Bones wrote: »

You have received answers.
You just don't like them.

Q. Name of a liquid concrete sealer
A. Liquid Vapour Membrane by partex

So I've received AN answer not answers as you've suggested

BryanF

here ends the witty banter, suitable concrete floor sealer products from now on thanks

hexosan

BryanF wrote: »

here ends the witty banter, suitable concrete floor sealer products from now on thanks

That's all I've wanted for the last 40+ posts

galwaytt

BryanF wrote: »

here ends the witty banter, suitable concrete floor sealer products from now on thanks

Polythene.

hexosan

galwaytt wrote: »

Polythene.

Dancing on the edge of witty banter 😄