Hi
Work is finishing on our new build extension - single room 6m x 7m. We have wet UFH (John Guest SpeedFit) with 3 loops in 75mm screed (4-1 sand mortar plus fibres) and we plan to glue a very good quality engineered oak board to it.
We left the screed 90 days to cure/dry, before commissioning the UFH. There have been two problems which have caused a number of 1mm cracks to appear:
1. Initially only one of the three flow valves was opened, meaning that for about 24 hours two of the loops remained cold while one heated up. This caused one third of the floor to expand, causing two cracks to appear in the cool section. These cracks go for about 2/3 of the 7m length of the room (same direction that the flooring will be laid), and run along the joins between the bands in which the screed was laid. They are wavy, with about +/-25mm deviation from a straight line. In a few places they have forked and rejoin.
2. I had been carefully warming up the UFH by 1-2 degrees a day as per instructions, but yesterday it somehow got cranked up by 6 degrees to 45 degrees. As a result, a number of new cracks have appeared, at right angles to the earlier ones.
My questions are - and sorry this is such a long post:
1. Are the cracks anything to worry about? Will things get worse over time? The screed itself seems to be sound, and the cracks have only appeared when something stupid happened.
2. What treatment, if any, should my builders use to repair them? Obviously I will make sure that everything else is done by the book from now on, though sometimes there is conflicting advice depending on who wrote "the book".
3. What is the very best flexible adhesive (regardless of cost), given any concerns about the cracks? BTW the manufacturer insists the boards should be glued down, and I do not want to use anything that would impair the efficiency of the UFH.
4. Any other Top Tips, except of the Captain Hindsight variety?
Thanks!
Work is finishing on our new build extension - single room 6m x 7m. We have wet UFH (John Guest SpeedFit) with 3 loops in 75mm screed (4-1 sand mortar plus fibres) and we plan to glue a very good quality engineered oak board to it.
We left the screed 90 days to cure/dry, before commissioning the UFH. There have been two problems which have caused a number of 1mm cracks to appear:
1. Initially only one of the three flow valves was opened, meaning that for about 24 hours two of the loops remained cold while one heated up. This caused one third of the floor to expand, causing two cracks to appear in the cool section. These cracks go for about 2/3 of the 7m length of the room (same direction that the flooring will be laid), and run along the joins between the bands in which the screed was laid. They are wavy, with about +/-25mm deviation from a straight line. In a few places they have forked and rejoin.
2. I had been carefully warming up the UFH by 1-2 degrees a day as per instructions, but yesterday it somehow got cranked up by 6 degrees to 45 degrees. As a result, a number of new cracks have appeared, at right angles to the earlier ones.
My questions are - and sorry this is such a long post:
1. Are the cracks anything to worry about? Will things get worse over time? The screed itself seems to be sound, and the cracks have only appeared when something stupid happened.
2. What treatment, if any, should my builders use to repair them? Obviously I will make sure that everything else is done by the book from now on, though sometimes there is conflicting advice depending on who wrote "the book".
3. What is the very best flexible adhesive (regardless of cost), given any concerns about the cracks? BTW the manufacturer insists the boards should be glued down, and I do not want to use anything that would impair the efficiency of the UFH.
4. Any other Top Tips, except of the Captain Hindsight variety?
Thanks!