Minimum thickness concrete screed??

[knonuffin]

Hello all,

What a fantastic site, I will recommend it to my friends here in France! OK creeping over, I have a terrace above garage attached to rear of house, which is 33m2, (3 x 11m). Please bear with me on this one, I’m having trouble getting the advice I need.

Basically, the previous owner began building the garage and terrace about 10 years ago, but sadly died before finishing the job. It was left with a concrete base which has, over the years deteriorated (house left empty all this time). I want to tile this terrace, but beforehand the floor needs screeding to provide a good base for the tiles, it is full of 'pock marks' at present.

There is a smaller terrace at the front of the house that is already tiled with about 20mm thick slabs and meets the larger, untiled terrace, leaving a difference of about 25 – 30mm depth.

There are two options that I am considering, one is to just screed the main terrace with a ‘self-smoothing’ screed that they sell here in 25kg bags (quite expensive at £18 per bag), then tile up to the level of front terrace. The other is to tile all round including over the existing slabs at the front. This would necessitate bringing the level of the side terrace up to that of the front, as said a difference of about 25-30mm. This is my preferred option due to the difference in materials.

Can I lay a concrete screed at this thickness, 25-30mm? It will be tile over and only foot traffic on it. Or is this too thin for concrete screed.

Thanks for taking time to read my ramblings, I will try to keep future postings shorter!

Regards,

Bob

[knonuffin]

OK, so what if I go ahead and lay the concrete screed at about 1", how about just a little hint at what mix ratio would be best, I've had all sorts of advice from friends, anything from 5-1 down to 2-1!!

Come on guys, help me out here. I know I waffled on a bit in my first posting but hey, we all do now and then, just be thankful I'd not had a few drinks; then I really do waffle!!

regards,

Bob

[knonuffin]

Well thanks for the replies!

I'm going ahead with this concrete screed at 30mm (1 1/4"), probably 3-1 mix, I will put on a good coating of adhesive, PVA or french equivelant.

It has been suggested that I incorporate fine gravel into this mix, is this neccessary?

Any other tips? I have been looking at the main pages, but I just need a bit of reassurance! Come on people, help me out here!!

Regards,

Bob

[Tony McC]

Don't panic if you don't get an immediate reply. Many of us have lives to lead and can't be in the Brew Cabin every day. In general, everyone gets a reply within 5 days, although it can drag on a bit if I'm away with my family in Ireland.

For your screed, I'd suggest using 6:1 coarse/sharp/grit sand with cement and possibly use a bind improver such as SBR or Ronafix, if they sell it in Franceland. I'm not a fan of PVA - it never seems to do what it is supposed to do and, as a bond enhancer....merde!

[simeonronacrete]

Bonjour Msr Knonuffin

Did you sort out your screed problem (I've just come across it).

Tony's right; Ronafix is technically superior to PVA and will last longer, especially if subject to water and frost.

See Ronafix For Screeds

Regards