Self leveling compound over new screed???

[Jamie25]

Been building an extension to my bungalow and made my first big mistake (that I've found so far).

Attempted to lay 7 tonnes of ready mixed screed in a day covering just over 42m2 and soon realized that after I'd shoveled and wheel barrowed it in up the steps then it was going off too quick for my dad and I to lay properly.

Rather than waste half of it we went for the 'just get it down quick and worry about a perfect finish later'. To add to that problem I tried to work it for too long on about the last quarter of the floor. After letting it cure for a couple of weeks the top 10mm was dusty in places and came up easily. The layer underneath seems to have cured properly stronger.

Looking at the self levelling options but as some areas are upto 10mm too shallow it's looking very costly. Don't think I can re-screed over this as a 10mm layer would be too thin. Don't want to rip it all up because of the UFH pipes.

The floor construction is Block and beam, DPM, 100mm insulation, VCL, underfloor heating water pipes, poorly laid screed circa 65mm+. I shall be tiling once I get a level floor.

Is water based self levelling compund my best option? If so how long should I let the screed dry out before using the SLC?

Cheers, Jamie

 

[Jamie25]

So having researched it some more I can only think that SLC is my only option. Looking at Mapei Ultraplan Renovation Screed as it seems to get good reviews and is competitively priced. That said it's still going to cost me 22 bags and £400.

Can anyone tell me if I have to let the original screed dry out properly? About two months using the '1 day per mm' rule???

 

[dazlight]

If your laying ceramics down on top you should be ok to screed ontop now.
If using a water mix though make sure you prime the floor 1st.

 

[Jamie25]

Thanks Dazlight. Not sure which kind of tiles I'm going to lay but definitely tiles.

Don't mind not laying the tiles for a couple of months, plenty of plaster boarding, skimming, kitchen installing, wiring, boiler installing to take up evenings and days off before tiling!

Just keen to get the floor leveled asap. I can only think that as they're both cement and water based I should be okay laying now.

Cheers again.

 

[dazlight]

If your going the Karndean type tiles. Vinyl, you will need to let the floor dry out to below 75% RH.
When you do the screeding get a spike roller as this will help alot mate