Replies

1. Expert Member
   Michael Maines | Feb 23, 2021 01:58pm | #1

   I've done it several ways but prefer to install either solid wood or a high-quality engineered wood (real wood veneer on a plywood substrate) over 3/4" Advantech screwed and glued to the concrete.

1. 
   arnoldk | Feb 23, 2021 02:38pm | #3

   Hi Michael,

   That was the option I was leaning towards. Did you install any vapor barrier before installing the Advantech on the concrete?

   Thanks,
   Arnold

1. Expert Member
   Michael Maines | Feb 23, 2021 04:22pm | #5

   Arnold, if you know there is a good vapor retarder below the concrete and it's on a layer of crushed stone that allows good drainage and acts as a capillary break, you don't need to add an additional layer of poly. There is a pervasive opinion in construction that any wood that touches concrete needs to be pressure treated. That's not exactly true--if the concrete is well-protected from moisture, as a slab on grade should be, any wood can be installed directly on the concrete.

1. 
   arnoldk | Feb 23, 2021 06:26pm | #6

   Thanks for the that Michael.
   The slab will likely be 4 feet above the surround grade with at least 6 inches of crush stone, 8" EPS and a 10 mil poly (also for Radon).

   I'm starting to see why people simply go with polish concrete but my wife hates it and will not budge on that.

   Arnold

1. Expert Member
   Michael Maines | Feb 23, 2021 06:47pm | #7

   You should have no need for additional poly then. I add poly when going over an existing garage slab or basement slab, but I prefer to glue the Advantech to the concrete when possible. Just be sure to use the short cleats!

   Many of my clients don't like the exposed concrete look, either polished or just sealed. I've started eliminating the concrete from the assembly in those cases, but it's still a new technique. Partly for carbon savings, but also for cost savings and access if anything went wrong such as a burst pipe.

2. 
   arnoldk | Feb 24, 2021 08:47am | #10

   Hi Michael,

   I briefly looked into foregoing the concrete slab but just like using composting toilets for our build, it wasn't worth the headache and very likely higher cost because it falls outside of the norm for the City development department and inspectors.

   Arnold

2. 
   craigcarter | Nov 15, 2021 09:20pm | #13

   Michael,

   I had just posted a question and a link to this thread came up...In reading the attached article I know I will have a good vapor barrier below the slab...however, I think the concrete will/may still be considered wet by the time I am ready for flooring. Is there a way to test the moisture content of the slab to know if any added moisture will be coming from the curing process or should I simply follow the recommendation by Joe Lstiburek and apply a fluid applied vapor barrier prior to installing Advantech subfloor?

   
2. 
   JC72 | Feb 23, 2021 02:10pm | #2

   In 1999 my builder glued the engineered (T&G) hardwood straight onto the concrete. Today there are only a couple of places where I can hear a faint "pop" where a particular plank has let go. It's obviously not the "right way" to install hardwood flooring on a slab but it's what they did in 1999.

1. 
   arnoldk | Feb 23, 2021 02:40pm | #4

   Thank you John for your feedback. I am concern that long term things may not hold very well but I am not sure if the glues are better these days. All my experience is with nailing with L-cleat and they all still in good shape.

   Arnold

3. Expert Member
   Peter Engle | Feb 23, 2021 08:14pm | #8

   There are a number of adhesive systems now that allow direct application to concrete. They work well, but they are very sensitive to installation quality. Make sure to follow all manufacturer's installation instructions. Conditioning the wood in the space is important.

   There are also floating floor systems using clips to join the boards. No adhesive or underlayment required, but special groove in the boards. Just installed over a slip sheet on top of the concrete.

   Any of these systems are acceptable, especially over a slab as well protected as yours. You do need to wait until the concrete has dried out. Testing the concrete for moisture is mandatory.

1. 
   arnoldk | Feb 24, 2021 08:42am | #9

   Hi Peter,

   Thanks for your response. I wanted to go with click floating floor but the manufacture my wife wants to go with (no VOC and Green Guard certified) has very limited option for their click flooring and they only have one plank size, 3/8" x 5-3/4".

   Arnold

4. 
   MaineLaxRef | Feb 24, 2021 10:13am | #11

   You might want to evaluate Steller Flooring. They have developed a plastic locking strip that allows their hardwood flooring to be installed with neither glue nor nails. Their product comes prefinished, so no sanding or finishing after the floor is laid. If a plank gets damaged, then you can use a vacuum grip to pop out a single plank to be refinished or relocated.

1. 
   arnoldk | Feb 24, 2021 10:41am | #12

   I looked into using their product but it's very expensive at around $14-$15 US per sq. ft. which makes it even more expensive since I live in Canada. It's not really a feasible option for me unfortunately.

   Arnold

5. 
   dfvellone | Nov 17, 2021 09:38am | #14

   I installed 2x4 sleepers using construction adhesive and mechanical fasteners over a slab-on-grade that had xps and vapor barrier beneath. Hardwood flooring has held up well with no issues at all some 30 years later.