I am laying tile in my living room. I have a sliding door to the balcony which have a door casing made of two stacking 2x4s. Previously it was wrapped by carpet as a stair. As shown in picture the people who did the carpet used a piece of drywall to match the thickness of surrounding walls and then just stapled the carpet to it. The drywall degraded due to moisture and the condensation water dropped from the sliding doors.

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What are my options to deal with this step? I could attach 1/2 MDF to both top and side then paint them, then attach baseboard to transition to the tiles, but I worry about the moisture.

1 Answer 1


Don't do it with MDF. MDF is way too soft material, and once water gets to it, it will be ruined very quickly. This is a place that sees lots of dirt and foot traffic. You need a hard and strong material, and durable and washable finish here.

  1. Buy two pieces of hardwood (maple, oak, etc.).
  2. Cut them to size: top piece should have a slight overhang, and front piece should be 1/8" (3mm) less than the height needed.
  3. "Ease" the front edge of the top piece (make it more round): a hand plane would do, or just a piece of sandpaper.
  4. Nail them to 2x4, the front piece should have a small gap at the bottom (it will be covered by tiles, but will allow the wood to move seasonally).
  5. Fill the nail holes, sand and finish them to match your door frame: oil-based glossy paint will be most durable solution.
  • It is a good idea to attach the two pieces of wood together prior to installation. That way, you can nail and glue the two pieces together and not have any gaps. This will allow you to round over the top with a router, and make a much smoother transition since there will not be a lip. The finish should also be done prior to the installation because all exposed surfaces of the wood should be sealed. It would not be possible to do this after installation. Afterwords, the finish can be touched up where the nail holes are. Commented Mar 27, 2017 at 14:27
  • You can also wrap the exposed 2x4 in a self sealing membrane such as Grace to make the wood below impervious to moisture. This, combined with construction adhesive will greatly help the sill from squeaking, and eventually cracking in the future. Long finish nails would hold it in place while the glue sets. Those holes would be easy to fill. Commented Mar 27, 2017 at 14:31
  • Pre-finishing is a good idea, but gluing the two pieces together is probably not. You'll need to replace the top piece much sooner than the front one, and any possible gap will be hidden by the front lip. Worst case, a bead of caulk will hide it.
    – haimg
    Commented Mar 27, 2017 at 14:38

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