Measuring Screed Humidity

[Swindiff]

I have posted on here a while back about my undefloor heating project. I now finally have a floor again

I have had a liquid screed laid, Gylvon Thermio+ at a minumum thickness of 36mm and a maximum of 52mm, average was 48mm. Video of it going down here

screed.mp4 - https://drive.google.com/file/d/0BzMb6WfJ36jmdnhVOFdxZXlHVk0/view?usp=sharing

It was laid 12 days ago now, after the 3rd day I scrubbed the screed with a stiff broom to get the laitence up at the recommendation of the installer, this worked a treat, a lot easier than sanding when it had fully hardened, although in places where it had dried slightly quicker (by windows) it proved stubborn requiring a wire brush and some extra elbow grease.

Going to turn the heating on low in the next couple of days to speed up the drying process a bit. I know I need to check the humidity using a Hygrometer, but is a Tramex or Ball type specific for this purpose really necessary. Could I get away with using a considerably cheaper hygrometer in an air tight pocket sealed to the floor?

 

[Ajax123]

sweeping is suitable to assist in laitance removal but the screed should be mechanically abraded (I.e. Sanded) prior the application of bonded floor coverings. This is actually true of ALL screeds and concretes ... yes I know few people do it on traditional screeds but it is in the screed standards and it is the recommendation of the contract flooring association.

the underfloor heating MUST also be commissioned and run, regardless of drying time, before tiling commences and if you are using Stone Tiles you should use uncoupling.

In answer to your question though yes you can use a cheaper hygrometer. You could buy a hair hygrometer for £20. Place it on a couple of matchsticks or probably tile spacers might be better to create a small gap underneath and then cover the whole thing with a sheet of clear polythene weighted or stuck down at the edges. Make sure the hygrometer is calibrated before use and read it after about 4 hours. If it is over 75% its not yet dry so lift it and wait a while longer. if after the 4 ours it is below 75% leave it in place for 48 hours and then read it. It should be below 75% at this point to be considered dry. As a double check leave it in place for a further 24 hours and re read it. If it has not moved and is below 755 it is dry enough to tile to. If it has moved but both readings are below 75% its dry. If one reading is below and one is above 75% it is usually very nearly dry but not quite and either needs a little bit longer or you may be able to use Ditra as a back stop. If both readings are above 75% it is not yet dry enough and will require further drying.

make sure whatever you stick to the screed is stuck with a gypsum based adhesive.

CLear as mud...

 

[Ajax123]

I just watched the video....I guess theres good and bad in all trades...

 

[Stef]

I just watched the video....I guess theres good and bad in all trades...

Just watched it..

 

[Swindiff]

Whats wrong with the video?

 

[Swindiff]

Using Porcelain tiles, so have been told no need for a decoupling membrane. Going to prime with Tilemaster Prime Plus, mixed 3 part water 1 part primer, so a litre should cover my 30m2. Then use Tilemaster Anhyfix adhesive for the tiles.

I thought the purpose of the sanding was to remove the laitence, if the laitence has been removed why the need to also sand?

Cheers

 

[Swindiff]

So I was thinking of getting a few of these,

Digital Incubator Humidity Meter Fertile Egg Hatching Chicks Hygrometer Uk - http://www.ebay.co.uk/itm/Digital-Incubator-Humidity-Meter-Fertile-Egg-Hatching-Chicks-Hygrometer-Uk/331348043318?_trksid=p2047675.c100005.m1851&_trkparms=aid%3D222007%26algo%3DSIC.MBE%26ao%3D1%26asc%3D20140122125356%26meid%3D4eb6d51993e4480bacf5bce692e5ff44%26pid%3D100005%26rk%3D2%26rkt%3D6%26sd%3D141117008251&clk_rvr_id=1092268619862&afsrc=1&rmvSB=true

sit them on a spacer so they are not in contact with the screed and tape some clear polythene over them so I can see the readings.

http://www.screwfix.com/p/harris-taskmasters-polythene-dust-sheet-roll-50m-x-2m/19574

Can anyone see any issues with this method?

 

[Ajax123]

just sweeping will simply not remove it all. sanding also removes any other debris

 

[Swindiff]

When I say sweeping, it was with a very stiff broom and the top crust came off in big flakes, must have been at least 1mm thick.

 

[jobdone]

What should it surface look like after it has been sanded? I have a liquid screed coming up (1st) it has been sanded but not sure if it is enough.

 

[Lee@emctiles]

Using Going to prime with Tilemaster Prime Plus, mixed 3 part water 1 part primer, so a litre should cover my 30m2. Then use Tilemaster Anhyfix adhesive for the tiles.

Well you are certainly using the correct adhesive, but listen to the advice from @Ajax123 as he's the don when it comes to these screeds. If he advisers mechanically sanding then take heed.

 

[Swindiff]

Cheers, does it matter what grout is used?

Still wondering what is wrong with how it was laid in the video?

 

[Ajax123]

What should it surface look like after it has been sanded? I have a liquid screed coming up (1st) it has been sanded but not sure if it is enough.

It will look similar to a very flat sand cement screed with no loosely bound or friable material on top. Check edges and corners especially

 

[jobdone]

It will look similar to a very flat sand cement screed with no loosely bound or friable material on top. Check edges and corners especially

Thanks bits of it look like a sand screed but most is still smooth and yellowish. I will get it sanded again.

 

[hmtiling]

It will look similar to a very flat sand cement screed with no loosely bound or friable material on top. Check edges and corners especially

Sorry to go off topic here but in another thread people have mentioned gypsum screeds being wavy and the only ones I've tiled(alpha-hemi) have been bang on level and flat. Do different brands go in less wet than the ones I've seen?