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Discussion Starter · #1 ·
Will this work? Planning a new project and there will be no baseboards on walls. Rather than leaving a reglet reveal at the floor, or taking the drywall right down to the floor, I am considering a new application (for me).

The plan is to hang the bottom course of drywall about 4-5 inches above the subfloor (concrete) using spacer blocks. Drywall the ceilings then walls as usual. Later, install the tile flooring up to the stud walls. Then, come in and install 1/2" MDF base in the gap over the tile floor and up to the bottom course of drywall. The MDF base will have a wide chamfer to match the taper of the drywall. Tape and mud that interface.

If this detail works as planned, the modern style wall will have the durability of having a flush baseboard and the baseboard will not be visible once the wall is painted.

Here are a couple pictures of a small prototype wall. Will this work and last? Any potential problems?





Comments appreciated.
 

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I have successfully taped drywall to MDF so there is no issue there. The only thing that concerns me is that you have zero room for expansion and contraction and could have potential issues down the track leading to cracks.
 

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Discussion Starter · #3 ·
Yes, I was concerned about that potential issue, but have had no experience with this particular detail. So, I did a little research about the expansion and contraction of MDF and drywall. Drywall is sufficiently stable. MDF moves less than natural wood, but it will move with significant temperature and humidity changes, about .3 to .5 percent. Searching the web, I found a couple of references to taping MDF to drywall, one recommended installing backing so the fasteners for the MDF and drywall seam would be secured into the same piece of lumber. The other reference recommended beveling the MDF for the tape and mud, but no warning of movement or potential cracking.

In Arizona, we generally have low humidity, and the temperature inside most homes with air conditioning would normally be held to 65-80 F approx. Perhaps movement between these two materials would not cause a serious issue, more thinking and thoughts would be helpful. I emailed this question to USG technical, but no response, yet.

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we tape drywall to MDF on each job.....actually when we do aluminium doors or inside windows for 99% of them reveal is made of MDF.....with that answer USG just covers its back... everything is about insurance... and now for ex you can't take them to court .....now the ball is in your court
 

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Our crew has completed quite a few of these flush baseboards using the method @AZ Build described.

Key takeaways from our experience:
  • Apply RedGard on the MDF base first, then apply mud. This will allow drywall mud to stick to the MDF base much better.
  • For the transition between the drywall and MDF base, use a fiber-reinforced compound, such as 3M FPP-32-BB. This will strengthen the connection and prevent cracking.
  • Use flexible caulk for the transition between the flush baseboard and hardwood floor (or do not caulk the gap). This will allow the floor to expand and contract without causing hairline cracks in the drywall mud coat.
Alternatively, we use Dorsis Linus flush recessed baseboard - the L-shaped housing bracket provides the baseline for drywall and completely eliminates the need for spacer blocks. The insert is typically a painted hard-wearing MDF board which you can re-paint or even replace as needed, and for wet areas like bathrooms, you can glue in tile and have the same flush baseboard appearance.

It looks like this:

Wood Rectangle Beige Wood stain Floor


There are additional specs at Modern flush baseboard Dorsis Linus | Angelbau
 
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