Gents, your thoughts please... Went to look at a job yesterday where a new 4" thick concrete subfloor [looks like a typical sand/cement jobby] had been laid literally 1 week ago. [its was 4" as i could see the end profile] it had a mechanical dpm underneath. I had expected the subfloor to be reading very high m/c levels of 18-20%, as i measured a similar recently laid subfloor last week and that one was showing between 18-22% on my Testo 606-2, however much to my surprise, the readings were much lower than i expected, between 2.6 - 5.8 % [10 readings] It looked like a typical sand/cement mix with a lot of curved depressions where a float trowel has been used to move the material, i have however asked the client to ask his builder exactly what the mix was... I had already informed the client that it would likely be around 150 days before the subfloor is in a suitable condition to apply leveller and lay the new parquet floor he wants, the area is 28m2 btw... Does anyone have any input as to why the m/c levels are so low ??
The Testo works on pins doesn't it? If so it's just reading the mc at the top crust. With the dry weather we've had it would read low. Only way to get a reading of what's going on lower down is a box hygrometer or plug set in hole in the slab. Although it could be an additive as Mario says
Gaz we've mentioned about using hydrometers to you before ? If you keep using a pin meter to read concrete slabs you going to continue to have "Subfloor dilemma's" Just get your self a digital hydro box for £100 job done sorted !
Pin Meters are for wood aren't they? Get a hygromaster mine only cost £100 on eBay brand new complete with box.
As above...Dodgy using a pin meter on concrete...Flying blind there mate...I'd consider using a full spec dpm (98% RH) aswell. For the extra cost and piece of mind, it's well worth it IMO. I know you've got your favourite system though mate
Cheers for the input chaps, i do get it with the pins & concrete i do... i've told the client its gonna be 120 days minimum before a floor goes down, and he's happy to wait, i just can't get my head round why 2 recently laid slabs show such different readings with the same piece of kit...
Gazhugs, when you did a floorskills course, well what was you advised by the instructors about reading moisture? How did the instructor advice you to read moisture and what equipment did he advice you used? Did the instructor tell you that a pin meter will ONLY read wood moisture? Did the instructor advice you that a pin meter will not give a accurate reading on concrete, some concrete will read very wet when dry and other will read dry when actually wet ? why is this ? a pin meter works on electrical resistance. In theory, the more water present then teh higher the resistance, hence a higher reading, BUT if there is minimal water present at surface OR there is a ADDITIVE that has LOW conductive present at the surface then it will tell you its dry . Come on Gaz, put in to practice what you learnt. PS........ wood moisture is read on a scale of 0-30 depending on which meter you use. CONCRETE moisture is read in MC / CME on a scale of 0-6.9% depending on which meter. 6.9% being 100% RH. Bs Reads in RH... 65% max for stick down wood.
I was listening but in my defence i've slept a few times since then...I knew the s/f was obviously wet as it had only been laid a week ago, surprisingly dusty as well tbh, it was the lowish m/c levels that threw me hence the question, no worries about laying a floor on that subfloor till mid october at the earliest... A tramex expert2 has been ordered, I certainly do put into practice what i've learned at Floorskills and all the other courses i've been on, never a day goes by that i don't learn a bit of something to do with floors and all the issues they throw up...
