cracks between bays in screed

[sm_jamieson]

I layed my floor screed in bays using a half-strength SBR mix, and in a couple of bays the mix was a little too wet (easier to lay !), and they have shrunk slightly, opening up some 1-2mm cracks between the bays, and around these edges it sounds a little hollow / unbonded. The centre of the bays is rock solid - its just round the edges. What can I pour into the cracks to fill them up and hopefully penetrate under the hollow sections ? Something that has body to it, and is also very runny. Granite dust comes to mind. I have a few litres of SBR left. Thanks, Simon.

[The Natural Philosopher]

I used half a gallon of PVA to do this. yes, half a gallon. Kept pouring till it wouldn't' take any more.

After a week or so, the floor was rock solid.

Cracks could then be filled with levelling compound or similar. I just tiled over.

[sm_jamieson]

How much did you dilute it ? Simon.

[sm_jamieson]

This is screed on concrete, not over insulation. It it did not have a solid base, I *would* be worried. Simon.

[The Natural Philosopher]

I told you, fill with PVA and dont worry. It really works. No need to joint the tiles or anythink.Tight as a ducks arse.

[sm_jamieson]

Yes, I was just wondering how much you diluted it (if at all). Simon.

[The Natural Philosopher]

In the end I just used up the gallon I had without dilution. It was not glue grade. It was 'size my walls' grade. The carpenters said to do it. I was dubious, but it bloody well worked! I WAS over insulation and with UFH pipes and rebar in there as well.

[JTM]

I've been following this with interest.

I have a screed base about 45 sq. metres, maybe 2 to 3 inches thick over a concrete slab with UFH. There are some fine cracks in the screed and for a while when we turn the UFH on we can 'feel' and hear some slight movement when walking across the room. There are no 'bays' but there is an expansion gap all the way round the room

I was thinking of PVA to fill the fine cracks, but should I cut an expansion gap across the room? The plan is that the floor will eventually be covered with Karndene.

John

[Roger Chapman]

"Can I fit Karndean myself? Karndean is not a DIY product. Your local retailer will provide a supply and fit service ? or will be able to recommend someone who can."

Not for me then.