Options to repair cracked screed

[Alex 200274]

Hi All

 

I know there are numerous posts on screed cracking, however I have a question about options to repair my cracked screed flooring prior to tiling the floor at some point later in the year and wanted to get some thoughts. 

 

I had an extension done several years ago which was screeded with UFH installed (approx 70 sqm). The extension has been on pause due finances so it’s basically unfinished with the screed flooring still exposed. 

 

Over the past few years numerous hairline cracks have formed and some have remained as a hairline but several have widened to 2-4mm across with the cracks extending in a crazy paving fashion across the width of the room which is 4m. Some of the cracked ‘islands’ have dropped by a few mm compared to the level of the rest of the floor and I only assume if I had laid tiles a few years back these vertical movements may have caused cracking in the tiles. 

 

I think the cracking has happened due to celotex  which had a see saw effect prior the screed being poured. I was wondering if the sections dropping by a few mm or more is due to voids between the celotex and slab and some sections of the screed floor might be floating causing it to crack and settle at different heights (plumber said a slight see saw was fine and the weight of the screed would pin them down, I fell out and not seen him for the past few years). Logically I thought the weight of the screed would pin down some of the celotex, but now wondering if they should have pinned it to the slab. 

 

I plan to lay tiles towards the end of this year and I will add a decoupling layer but I’m aware this is only ok for lateral movements but not vertical and worried if new cracks appear with vertical drops then it may transfer as cracks through the tiles.

 

1. Do you think the larger cracks could be filled with resin using something like the Uzin repair kits (basically resin with bridging strips inserted between the cracked sections)
2. As there is no expansion joints - room is L shaped - 10m by 4m and then 5m by 5m, should I leave some of the cracks open, wasn’t sure if this acted as an expansion joint?
3. I wasn’t sure if I should leave the floor as is and the prior to tiling overboard with OSB or ply and then place a decoupling layer  - I was thinking the boards could act as a bridge future proofing any possible further cracking once tiled. The boards could be glued and screwed (although this could be a recipe for disaster as the UFH pipes may be struck)
4. Alternatively, if resin kits don’t work and the issues I have is probably symptoms of a poor substrate then worse case I could lay a floating wood floor, and I was thinking this might have some flex, but for practicality being a kitchen area and walkway from the garden + UFH, I wanted tiles

 

The main advantage I have is time on my side as we have a temporary working kitchen. I don’t have the option to rip it up and start again. Photo attached is an example of one of the cracks, that one is  3m in length and then narrows but oddly the screed doesn’t rock, in fact it doesn’t rock in any of the places, but there are hollow sounds when tapping but not sure if that is typical with screed. 

 

 

 

 

 

 

[nod]

There is no need to repair prior to tiling 

Though it would benefit from matting prior to tiling