Joined: Feb. 2018
||Posted: 07 Feb. 2018,14:24
Tony's advice is spot-on. When I see this it's mainly due to varying porosity of blocks and is more noticeable when newly installed, over time it lessens. Another reason can be bagged aggregates being much wetter than others providing a patchy-in-terms-of-dampness screed that's perfectly sound (as long as it's not absolutely soaked and making the blocks pump). That'd take a few months to sort itself out at this time of year. Hopefully it's nothing more serious than either of those - it's not likely to be.
From an installer's POV, the best way to avoid the whole drive looking patchy is to, as we all should anyway, install from a number of packs instead of consecutive packs. It's not always possible on smaller jobs and when your delivery driver has dropped your packs vertically stacked. Instead of large patches you have interspersed individual units remaining wet-looking, these will also "dry off" more readily being surrounded by drier units as they can draw the moisture. Still not ideal from a customer's perspective, but just one of those things.
After the fact, a simple way to lessen the effect is to use a very good quality jointing sand stabiliser such as the multicrete one I prefer. I had to do this on a small job where the packs of block looked identical but were of different batches and dried very differently. This not only ties that jointing sand together and avoids its removal, it also puts a sheen on the blocks that can last a year or more, and a side-effect of this is a much more uniform drying out.
EDIT - sorry, didn't realise this post was from a couple of months ago :blush:
Kevin W. Dempsey kwdConstruction http://www.kwdc.co.uk