I am not a contractor or flooring installer, so most of the info I am reading is beyond my level of understanding.. But my installer is getting a moisture reading (using a moisture meter I think) of my slab of 12% -14%. How reliable is using the moisture meter for assessing compatibility of bamboo with the concrete slab? We are trying to trouble shoot a bamboo floor that has swollen in several sections. Some of the swelling was on the new concrete slab on grade and some on the older slab. Slab was poured in September (for the remodel) of last year and floor installed in January of this year. Problems occurred between April and September. Floating bamboo floor over Aquabar "B" barrier.
What product would you recommend for up in Seattle? How reliable are moisture meters? Should we do the drilling into concrete slab for a confirmation of moisture values? Thanks
11-03-2010, 07:04 PM
(This post was last modified: 11-04-2010, 08:09 PM by Ernesto.)
I like a trowel on vapor retarder like Bostik MVP4. Proven over and over if the concrete is tested properly. Yes, do both rh and cacl if your experiencing problems. And fire the installer/contractor.
I tried to reply to your email but you must have a filter that requires signing my way through.
Where do we start with this situation? There are so many factors to consider.... The old slab must have an intact vapor retarder directly under it (no blotter layer) or you should consider it very wet no matter what the current reading is. If the retarder is old it could be deteriorated and failing. The new slab must have a quality retarder placed directly under the concrete.
Considering you have these retarders in place, proper moisture testing should be done. I don't know what you mean when you say 12% - 14% moisture. That would be extremely high for an electrical impedance meter and impossibly low for an RH test. CaCl tests could be 12 - 14 lbs, but that would be VERY wet. Of course the testing done could be improperly performed and that would explain the numbers.
Swelling in localized areas could be due to concrete cracks, joints or trenches. I'd pop open an areas and take a look.
Concrete Answers for Flooring Problems
I don't know what you mean when you say 12% - 14% moisture. That would be extremely high for an electrical impedance meter and impossibly low for an RH test. CaCl tests could be 12 - 14 lbs, but that would be VERY wet. Of course the testing done could be improperly performed and that would explain the numbers.
Must be using a wood encounter meter. My CME only goes up to 6 %.
CACL test was 4.04 % . ASsuming this is accurate should it be safe to re install the bamboo? Should some sort of sealer go on the concrete + the Aquabar "B" that was used previously?
You need a moisture control system like Bostik MVP4 or better. And NO to the aquabar. Ddin't you read the pdf link I posted?
Ok Yes read the PDF , but not being that familiar with flooring installation I probably did not completely comprehend. OK so given I do not have a plywood sub floor..just the bamboo with a green foam like backing on it's underside going onto a concrete slab on grade (originally over the Aquabar)..you are saying Moistop ultra goes on top of the slab and then the bamboo??? My floor is a floating floor and the specs for MVP4 say it is for glue down floors only!
It's really not that much to understand, just calmly look at your situation. I wish I was there to see what you see.
Let's take things in order:
1: Determine the required moisture emission rate limit of the flooring.
2: Measure the moisture vapor emission rate (MVER) of your slab.
3: Determine if you can trust the MVER readings.
4: If 2&3 are good, install the floor.
5: If 2 or 3 are poor, install a good moisture mitigation system.
Number 3 is where 90% of moisture caused failures occur. Number 5 is where people realize applying snake oil will not give long term satisfactory results.
We have emailed back and forth and I think you need more information about your slab. If it has a blotter layer I would not trust any readings. A blotter layer is a layer of porous and permeable aggregate installed between the vapor retarder and the slab. Blotter layers will allow large amounts of water to move freely below the slab through vapor barrier punctures and rips or from the sides of the slab. A blotter layer can be bone dry one month and soaking wet the next. Never trust MVER readings over a blotter layer.
Can you be sure the vapor retarder is in excellent condition? No cuts, tears, holes? Less than 12 years old? (most older slabs were poured over 4-6 mil polyethylene sheets, and that can degrade significantly over time.) Are there cracks and joints in the slab that may allow water migration?
If you are SURE the vapor retarder is in excellent condition and placed properly, and you get accurate and reliable MVER tests (follow the ASTM to the letter!) then a slab with a 4lb CaCl test reading should be completely suitable for bamboo installation.
But you still need more information. You only have 1 MVER test, and those tests are very susceptible to errors. Your impedance meter is extremely high and you have swelled bamboo. You are missing the key to explaining all these factors.
Don't give up!
Concrete Answers for Flooring Problems