Porthole Posted February 12, 2022 Share Posted February 12, 2022 Hi there Had a sand and cement screed said about 3 weeks ago (approx). There is a hairline crack now which is at 45 degrees to the corner of a wall (which supports a steel). The heating has been on at around 40 degrees constantly over last week or so. Don't know if that has caused it. Please can someone tell me what should be done. The builder spoke about raking it out and then putting latex in. Tiler didn't think you need to worry about hairline cracks only if bigger say 10mm. Your views gratefully received. Many thanks Link to comment Share on other sites More sharing options...
nod Posted February 12, 2022 Share Posted February 12, 2022 Short answer is nothing It’s unusual for screeds not to crack Link to comment Share on other sites More sharing options...
Nickfromwales Posted February 12, 2022 Share Posted February 12, 2022 (edited) Hairline cracks in screed are commonplace. Lost count of how many floors I’ve had put down and had subsequently cracked in more than one place, and were tiled over without issue. Relax. At the VERY worst, if the crack was ‘serious’ or lots of them, you’d ask your tiler to install a decoupling membrane ( like Ditra Mat etc ) and sleep well. What size is the screeded area? Edited February 12, 2022 by Nickfromwales Link to comment Share on other sites More sharing options...
Nickfromwales Posted February 12, 2022 Share Posted February 12, 2022 Oh, and turn the heating down! 40oC is too hot for a new / fresh screed. That deffo didn’t help 30oC max for a month. Link to comment Share on other sites More sharing options...
Porthole Posted February 12, 2022 Author Share Posted February 12, 2022 Many thanks Nick - that's really helpful. Tiler is installing ditra anyway so that's good. We'll make sure heating is turned down!!! I thought it was a bit high - should trust our instinct next time. Link to comment Share on other sites More sharing options...
Nickfromwales Posted February 12, 2022 Share Posted February 12, 2022 8 minutes ago, Porthole said: Many thanks Nick - that's really helpful. Tiler is installing ditra anyway so that's good. We'll make sure heating is turned down!!! I thought it was a bit high - should trust our instinct next time. Needs to be off / slab cold for at least 48hrs before going anywhere near it with tile adhesive. That’s for the Ditra too. Mop the dry screed with 50/50 primer and water until pretty much saturated. Old school janitors mop is the weapon of choice, and mopping gets all the dust / surface contamination dealt with. Not lost a tiled floor in nearly 3 decades of tiling. Do NOT turn the UFH back on for a minimum of 2 weeks after laying, and then start at the lowest temp and increase by 2oC every 48hrs. Link to comment Share on other sites More sharing options...
nod Posted February 12, 2022 Share Posted February 12, 2022 1 hour ago, Porthole said: Many thanks Nick - that's really helpful. Tiler is installing ditra anyway so that's good. We'll make sure heating is turned down!!! I thought it was a bit high - should trust our instinct next time. Make sure tiler puts expansion joints across EVERY doorway 1 Link to comment Share on other sites More sharing options...
Nickfromwales Posted February 12, 2022 Share Posted February 12, 2022 Low temp slab can usually get away without expansion joints, but deffo good insurance with screed. ?? Link to comment Share on other sites More sharing options...
nod Posted February 12, 2022 Share Posted February 12, 2022 11 minutes ago, Nickfromwales said: Low temp slab can usually get away without expansion joints, but deffo good insurance with screed. ?? We always put them in regardless of UFH and matting There should be expansion joints in the screed also Nearly always crack in doorways Link to comment Share on other sites More sharing options...
Nickfromwales Posted February 12, 2022 Share Posted February 12, 2022 19 minutes ago, nod said: We always put them in regardless of UFH and matting There should be expansion joints in the screed also Nearly always crack in doorways Got 140m2 of tiles down over a passive raft with low temp UFH. Done loads, zero cracks, not even hairline. The clash of the tiling titans may now commence!! ?? Link to comment Share on other sites More sharing options...
Onoff Posted February 12, 2022 Share Posted February 12, 2022 13 minutes ago, Nickfromwales said: Got 140m2 of tiles down over a passive raft with low temp UFH. Done loads, zero cracks, not even hairline. The clash of the tiling titans may now commence!! ?? A142 mesh? Link to comment Share on other sites More sharing options...
Nickfromwales Posted February 12, 2022 Share Posted February 12, 2022 24 minutes ago, Onoff said: A142 mesh? Yup. Plus ring and intersectional steels. Link to comment Share on other sites More sharing options...
Nickfromwales Posted February 12, 2022 Share Posted February 12, 2022 (edited) 28 minutes ago, Onoff said: A142 mesh? @JSH laid travertine over his constructional raft and no issues. If you talk too loudly around travertine it will break, so good enough for him, good enough for me……good enough for anybody. Edited February 12, 2022 by Nickfromwales Link to comment Share on other sites More sharing options...
Pocster Posted February 12, 2022 Share Posted February 12, 2022 59 minutes ago, Nickfromwales said: The clash of the tiling titans may now commence!! ?? You summoned me ? 2 1 Link to comment Share on other sites More sharing options...
Onoff Posted February 12, 2022 Share Posted February 12, 2022 4 hours ago, pocster said: You summoned me ? That would have been clash of the tiling tits! Link to comment Share on other sites More sharing options...
Pocster Posted February 12, 2022 Share Posted February 12, 2022 8 minutes ago, Onoff said: That would have been clash of the tiling tits! Reminds me of a pornhub film I watched Link to comment Share on other sites More sharing options...
Porthole Posted February 13, 2022 Author Share Posted February 13, 2022 On 12/02/2022 at 10:28, Nickfromwales said: Needs to be off / slab cold for at least 48hrs before going anywhere near it with tile adhesive. That’s for the Ditra too. Mop the dry screed with 50/50 primer and water until pretty much saturated. Old school janitors mop is the weapon of choice, and mopping gets all the dust / surface contamination dealt with. Not lost a tiled floor in nearly 3 decades of tiling. Do NOT turn the UFH back on for a minimum of 2 weeks after laying, and then start at the lowest temp and increase by 2oC every 48hrs. Thanks Nick for your tips Link to comment Share on other sites More sharing options...
Adsibob Posted February 13, 2022 Share Posted February 13, 2022 So having boasted about my screed not having any cracks in it (somewhere else on this forum), I spotted a long, but thankfully thin, crack in my screed. It is about 2.5m to 3m long, but less than a mm wide. Slightly jagged with no real explanation as there is nothing different either side of the crack, it is more or less in the middle of the room. My architect thinks it’s just the building settling. Screed was poured 125 days ago and I only spotted this crack a couple of days ago. UFH went on about 8 weeks ago (around day 70 after the pour). Hopefully there aren’t any more cracks and that this crack doesn’t get any bigger, but I guess it must be fairly common. We are planning on laying a microcement topping which is 3.5mm thick. Not sure whether I need to fill this tiny crack with anything beforehand. Link to comment Share on other sites More sharing options...
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