I am doing a bathroom and lavatory refit. I will have to replace most of the floor screed in the toilet. An area of about 1m x 1.5m 25mm thick.

I will use a 4:1 mix

I expect similar problems in the bathroom and will repair screed and tile walls first leaving the bottom cut row until I can tile the floor.


How long do I need to wait before tiling the floor ?

Can I reduce the time using a fast set cement ?

hi best to let it dry naturally 1mm needs 1 days drying if its 25mm thick give it 25 days why did the screed need replacing

Poor mix some 50 years ago. I had a similar problem 20 years ago when I was tiling sitting room. I suspect some areas were too dry. The area under the toilet seems OK. Some areas are a bit pitted and dusty where old thermoplastic tiles laid on a bitumen layer were removed. I will have to seal those areas somehow after replacing the screed to make the toilet accessible. I will do the screed late today so that the toilet is out of operation just overnight. (We have a caravan we can use).

Easy T

Don't really fancy having to leave it for 3 weeks.

take it you use a slurry coat before screeding

I think mapei have brought out a green screed adhesive

Floor with part screed removed showing plastic sheet over concrete and remaining screed.

Originally Posted by jay

take it you use a slurry coat before screeding

I was just going to lay on plastic membrane. No slurry coat. pva the existing abutting edges and a little in the mix.

I am open to advice though.

if you have a concrete base remove plastic to let screed to stick

dont repeat dont use pva find an acrylic primer dampen concrete slightly apply primer mixed with water (check directions) sprinkle neat cement on top mix together using stiff brush (slurry coat) then lay screed on top make sure slurry coat stays wet and this will help it to bond hope this helps

Thanks for the advice Jay. As all the existing screeds are laid on a visqueen (SP?) layer over the concrete I assumed that this was to do with damproofing.

Originally Posted by easyt

Thanks for the advice Jay. As all the existing screeds are laid on a visqueen (SP?) layer over the concrete I assumed that this was to do with damproofing.

if you have any concerns with damp you can use a waterproofing over the top of the new screed contact wetdeck he knows his stuff hope this helps

Can I reduce the time using a fast set cement ?

Yes, use BAL Quickset Cement in place of OPC in your screed mix and you can be tiling in 24 hours

BAL Adhesives - Products - quickset cement

Originally Posted by jay

if you have a concrete base remove plastic to let screed to stick

dont repeat dont use pva find an acrylic primer dampen concrete slightly apply primer mixed with water (check directions) sprinkle neat cement on top mix together using stiff brush (slurry coat) then lay screed on top make sure slurry coat stays wet and this will help it to bond hope this helps

Do you always have to use a slurry coat on concrete before screeding, or is it just best practice/reccomended?
What are the likely consequences of not using a slurry coat?

Cheers

Wetdec has gone/is going on his hols

i use ultra slc tile over day after

about fortnight or Bal do an adhesive called Bal Green Screed which u can use 24hrs after laying ur new screed

Originally Posted by JamesBrownLive

Do you always have to use a slurry coat on concrete before screeding, or is it just best practice/reccomended?
What are the likely consequences of not using a slurry coat?

Cheers

more chance your screed wont stick to substrate if you dont use slurry coat

if you put in 4:1 sand cement screed at 25mm expect to be re laying it pretty soon. It is much too thin. If you are laying on an existing concrete or screed floor it needs to be 50mm minimum. If you are stuck with 25mm I would mix 3:1 and add SBR and polypropylene fibres. This would also dry significantly quicker as the SBR will reduce the water content and the water cement ratio will be lower meaning more of the water in the mix is used up by the cement hydration.

Originally Posted by Ajax123

if you put in 4:1 sand cement screed at 25mm expect to be re laying it pretty soon. It is much too thin. If you are laying on an existing concrete or screed floor it needs to be 50mm minimum. If you are stuck with 25mm I would mix 3:1 and add SBR and polypropylene fibres. This would also dry significantly quicker as the SBR will reduce the water content and the water cement ratio will be lower meaning more of the water in the mix is used up by the cement hydration.

I know that it is too thin. Having said that there was no noticeable problem until I ripped up the thermoplastic tiles. The house is 55 years old. If the problem recurs in half that time it is unlikely to be my problem.

I think that I will keep the mix on the strong side. When they built the house they must have had poor control over the base concrete levels. Screed about 23mm in toilet - In bathroom about 45 - In sitting room it was over 50mm.

I will probably remove the plastic membrane from the failed area and bond the screed directly to the floor slab. In the adjoining bathroom there was no general problem. Screed has failed over existing pipes in a small 500mm x 75mm area. Cover to pipes is probably only 20mm.

Why not bed 20mm wedi type board onto the floor with adhesive then tile that the same day.

Every one is a winner

Good luck

Terry
On The Tiles - Professional Tiling Service - High Quality Tiling London

dohh. Thanks Good idea.

(Wish I hadn't just laid the screed).

Originally Posted by terrygrant

Why not bed 20mm wedi type board onto the floor with adhesive then tile that the same day.

Every one is a winner

Good luck

Terry
On The Tiles - Professional Tiling Service - High Quality Tiling London

Do you still need to use an isolation membrane with Wedi boards? Or does the fact they have a styrofoam core provide that functionality?

Cheers

No membrane required. Wedi is dimensionally stable in all conditions excepting perhaps a house fire. Its quick and easy to fit, it allows you to level out a floor, it has great insulation properties.....I just whish I had developed it!

Terry
On The Tiles - Professional Tiling Service - High Quality Tiling London

Originally Posted by terrygrant

No membrane required. Wedi is dimensionally stable in all conditions excepting perhaps a house fire. Its quick and easy to fit, it allows you to level out a floor, it has great insulation properties.....I just whish I had developed it!

Terry
On The Tiles - Professional Tiling Service - High Quality Tiling London

In your professional opinion, how do you rate it next to Marmox?

Cheers