Big ish refurb - a few questions

[EternalOptimist]

Moved out of the house while the builders are in - starting to get close to finished now, but there are a few questions you might be able to help me with. The ground floor hasn't changed - it's a solid slab which had 25mm of polystyrene insulation on top, with a 22mm chip floor sitting on top, screwed though to the slab. That had a solid wood block floor on top of it.

All that has been ripped up (except the slab). There are a couple of bits of new floor that have gone down where we've changed the shape of a couple of rooms - there's 60mm of screed that was put down last week to the same height as the existing slab.

Drying time at 1mm/week is a bit of a problem - I want to get a floor down so I can get the kitchen in which will allow us to move back in - usual story!

I've read about the adhesives I can use on green screed - Not sure that wil work for what I want to do - I'm thinking about using a marmox type tilebacker board, (c.40mm) electric underfloor heating, then tiles on top (in the kitchen and utility)

Does that sound sensible? NB the slab is rough - nothing like as smooth as a screeded surface, not sure if the tile backer would sit nice and flat....

All advice greatfully appreciated....

[david campbell]

you could level the backer board onto the slab with a flexible adhesive!

[EternalOptimist]

Cheers - how much height variation will the flexi adhesive cope with? Would that be OK over green screed?

[grumpygrouter]

If the floor is not too uneven, you may well get away with laying a decoupling membrane first. This will allow your new screed to dry correctly.

SCRUB THAT....JUST RE-READ THE POST. MISSED THE BIT ABOUT UFH....

[Dave]

When you say rough finish, then how rough...?

[doug boardley]

I'd be tempted to cover in a flexible slc to start with

[Dave]

Not onto a green screed doug....won't take with the residule moisture in the screed..

[david campbell]

I'd be tempted to cover in a flexible slc to start with
good thinking doug!

[Daz]

Drying time at 1mm/week is a bit of a problem

I normally allow 1mm per day. I.e 60mm screed is 60 days drying time.

Still not ideal for you but saves waiting a year for the screed to dry .

[EternalOptimist]

When you say rough finish, then how rough...?

Around 10mm high to low - looks like the original builder got it level with the edge of a board rather than smooth with a float.

[doug boardley]

Not onto a green screed doug....won't take with the residule moisture in the screed..

never saw that bit (60mm) in thread, laptop playing silly games on me!

[Dave]

Around 10mm high to low - looks like the original builder got it level with the edge of a board rather than smooth with a float.

OK.....Use a green screed adhesive mixed slightly wetter than normal and float the ridges in to get it flat....then when set use the green screed adhesive again to lay a vapour equalisation membrane...this will allow the floor to dry out and cope with any curling of the screed...

You can then lay your ufh on top of the Ditra and float the mat in with flexible adhesive to hold it down and give a better surface to tile too..


You cannot apply SLC to the new screed the residule moisture will pop it off...as the slc sets to fast to cope with the moisture..

hope this helps..

[Uheat]

Moved out of the house while the builders are in - starting to get close to finished now, but there are a few questions you might be able to help me with. The ground floor hasn't changed - it's a solid slab which had 25mm of polystyrene insulation on top, with a 22mm chip floor sitting on top, screwed though to the slab. That had a solid wood block floor on top of it.

All that has been ripped up (except the slab). There are a couple of bits of new floor that have gone down where we've changed the shape of a couple of rooms - there's 60mm of screed that was put down last week to the same height as the existing slab.

Drying time at 1mm/week is a bit of a problem - I want to get a floor down so I can get the kitchen in which will allow us to move back in - usual story!

I've read about the adhesives I can use on green screed - Not sure that wil work for what I want to do - I'm thinking about using a marmox type tilebacker board, (c.40mm) electric underfloor heating, then tiles on top (in the kitchen and utility)

Does that sound sensible? NB the slab is rough - nothing like as smooth as a screeded surface, not sure if the tile backer would sit nice and flat....

All advice greatfully appreciated....

Hi ya,

We have got insulation boards similar to Marmox which are cheaper they are called PCS and for a 40mm board you are looking at £16.91 per board. We also do another board called Ekoboard which does not have the reinforced skin to it but is still load bearing up to 30 tons/m2 and has the same U values. These would be £9.20 per board for 40mm.

If you have an idea of room sizes or even a plan send them to my email address aaron.frogley@pedarson.com and i will be happy to work out a costing for you.

Thanks

[Dave]

Aaron..this is a fresh screed and the boards will not allow the floor to dry out...

[EternalOptimist]

Aaron..this is a fresh screed and the boards will not allow the floor to dry out...

There's the nub of the problem - I've got to lay some insulation over the slab then the ufh then tiles to get the right final height - I can't lay tiles straight onto the slab

[Dave]

Just going back over your opening post...

How long has the screed been down..?

[EternalOptimist]

A week now.

I'm amazed how quickly people respond on this site!

[Dave]

Ok...A screed will be ok for normal flexible after 2 to 3 weeks normally....

If it's concrete then it's longer but screed is faster drying.

So a latex slc and then flexi adhesive and insulation boards from Uheat....

And if you want an even better deal then let Uheat quote for UFH and boards..

[EternalOptimist]

Thanks - very helpful