In a Vancouver concrete condo, the floor you can see is only half the job. The slab underneath holds moisture, and installing over a slab that is too wet is the most common reason a new floor fails. Testing first is cheap insurance. Here is how concrete subfloor moisture testing works, the number that matters, and why every slab install in the Lower Mainland deserves it.
Key takeaways
- Concrete slabs hold and release moisture long after they look dry.
- The industry test is ASTM F2170 in-situ relative humidity, with a common ceiling near 75 percent for many products.
- Skipping the test risks cupping, adhesive failure, and voided warranties.
- Always check the specific flooring manufacturer’s moisture limit before you install.
Why concrete is never as dry as it looks
A concrete slab can feel dry to the touch while still carrying moisture deep inside. In a coastal climate that moisture has somewhere to go, and it goes up into your flooring and adhesive. A surface that looks ready can still be well above the limit your floor can tolerate.
The test that matters: ASTM F2170
The recognized method is ASTM F2170, an in-situ relative humidity test using probes set into the slab. It reads the moisture deep in the concrete, not just at the surface, which is why it is far more reliable than older surface methods. Many manufacturers set a ceiling around 75 percent RH, though the exact number is product-specific.
What happens when you skip it
Install over a slab that is too wet and the results show up within months: cupped boards, adhesive that lets go, and trapped moisture problems beneath the floor. Most manufacturers also void their warranty if a moisture test was not done, so the cost lands entirely on the owner.
Reading the result and choosing a fix
If the slab passes, you proceed with the right underlay and adhesive. If it reads high, the options are a moisture-mitigation coating, a vapor-tolerant assembly, or a floating floor over a quality membrane. The reading drives the assembly, which is the whole point of testing first.
How Canadian Home Style handles it
We test the slab before we quote the assembly, match the product to the reading, and prepare the subfloor so the floor lasts. One local team from our North Vancouver showroom, accountable from slab to surface.
Book a showroom consultation or request an in-home consultation, and our team will spec the right floor and subfloor system for your home.
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Frequently asked questions
How long does a moisture test take?
ASTM F2170 probes typically need about 24 hours to equilibrate in the slab before an accurate reading, so plan for it in the schedule.
Can I install if the slab reads high?
Yes, with the right mitigation: a moisture coating, a vapor-tolerant membrane, or a floating assembly. The reading decides which.
Does new construction need testing too?
Especially so. Fresh slabs hold construction moisture for months, which is why new builds are a common failure case without testing.