Loz Posted July 28, 2021 Share Posted July 28, 2021 Hi, Builder has poured two separate concrete floors either side of a wall, the wall has now come down as going to be open plan area, and turns out floors are at different levels. The next step was going to be insulation board and then pipework on top for under floor heating and a liquid screed poured on top and then the long wait before porcelain tiles to finish. So today there was discussion on how to get floors to same level before putting the insulation board on top, the solution they came up with was to use sand they had on site to bring the lower floor up, don't think there is much difference in levels - about 20mm. Is this an acceptable/regular solution ? The kitchen with island is going on top of what is the lower floor raised with sand, guess will be quite compacted but concerned about movement or compression of floor over time. Area is about 4m by 4.5m. Any thoughts greatly appreciated, Lawrence Link to comment Share on other sites More sharing options...
Oz07 Posted July 28, 2021 Share Posted July 28, 2021 probably fine, maybe erring on a bit to thick. Split the difference? 1 Link to comment Share on other sites More sharing options...
Loz Posted July 28, 2021 Author Share Posted July 28, 2021 5 minutes ago, Oz07 said: probably fine, maybe erring on a bit to thick. Split the difference? Questioned it twice today so going to really annoy them to get them to pull board up and remove sand and go for thicker insulation or maybe extra screed on top, Many thanks, Lawrence Link to comment Share on other sites More sharing options...
Oz07 Posted July 28, 2021 Share Posted July 28, 2021 On most drawings you get told to use a sand blinding layer, not sure anyone ever really goes as thick as 20mm though. Maybe a couple of bags of cement raked into it if you were overly worried? Link to comment Share on other sites More sharing options...
Loz Posted July 28, 2021 Author Share Posted July 28, 2021 3 minutes ago, Oz07 said: On most drawings you get told to use a sand blinding layer, not sure anyone ever really goes as thick as 20mm though. Maybe a couple of bags of cement raked into it if you were overly worried? Cheers, guess as board is laid on top whatever I get them to do now involves them undoing what they did today and probably annoying them as they said twice is okay but really worried about problem further down the line, Many thanks, Lawrence Link to comment Share on other sites More sharing options...
Oz07 Posted July 28, 2021 Share Posted July 28, 2021 Maybe someone else would like to chip in but 20mm is probably okay. Google search for "maximum thickness sand blinding layer" 1 Link to comment Share on other sites More sharing options...
PeterW Posted July 28, 2021 Share Posted July 28, 2021 27 minutes ago, Loz said: Questioned it twice today so going to really annoy them to get them to pull board up What board ..? Insulation ..? 20mm is ok as long as it’s compacted and levelled and not just chucked down. 1 Link to comment Share on other sites More sharing options...
saveasteading Posted July 28, 2021 Share Posted July 28, 2021 Everbody is correct. The only issue with 20mm sand is that, however well laid and compacted, it kicks up as soon as anyone stands on it. Then you get not only loose areas, but differences in thickness. IF they have a way of getting it level and keeping it that way, then all may be well. Next insulation you say? That is strong enough to take pedestrians and spread the weight . Then I suggest putting a board on it and jumping to even the sand under the insulation, or there may be hollows. On the other hand 10mm more screed is 0.4m3, so not a great cost. Or mix sand and cement as mentioned. 0.4m3, with free sand? That seems to be the answer. Link to comment Share on other sites More sharing options...
Loz Posted July 28, 2021 Author Share Posted July 28, 2021 20 minutes ago, saveasteading said: Everbody is correct. The only issue with 20mm sand is that, however well laid and compacted, it kicks up as soon as anyone stands on it. Then you get not only loose areas, but differences in thickness. IF they have a way of getting it level and keeping it that way, then all may be well. Next insulation you say? That is strong enough to take pedestrians and spread the weight . Then I suggest putting a board on it and jumping to even the sand under the insulation, or there may be hollows. On the other hand 10mm more screed is 0.4m3, so not a great cost. Or mix sand and cement as mentioned. 0.4m3, with free sand? That seems to be the answer. Thanks for all the replies, my worry is lack of compaction, sand laid, levelled and then insulation board laid on top, as far as I can tell no compaction been done other than walking on Insulation board, just seems of all the solutions this seems most risky, tempted to ask for either thicker board, more screed or a different mixture as suggested, Many thanks, Lawrence Link to comment Share on other sites More sharing options...
tonyshouse Posted July 28, 2021 Share Posted July 28, 2021 I would rake cement into the sand 8:1 - common practice to level out undulations. Sheet insulation would work too Link to comment Share on other sites More sharing options...
Temp Posted July 28, 2021 Share Posted July 28, 2021 (edited) +1 You can get 20mm insulation board. Check floor is level with laser first. If not level use sand. Edited July 28, 2021 by Temp Link to comment Share on other sites More sharing options...
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