Terry has a second-floor condo in South Florida where sliding storm doors were installed, leaving a 1 1/2” deep, 12” high, and 13’ wide gap above a built-out section of the interior balcony wall. He wants to know if he can use foam board to fill the space and apply a light decorative stucco skim coat to blend it with the existing walls.
Question from Terry: Hi. Thanks for taking questions. On our balcony here in South Florida, we had our screen replaced with sliding storm doors. Since our second-floor condo required the existing handrails to remain per code and HOA rules, the contractor had to "build out" the interior upper wall a bit to make the install work.
This has left a space above the build-out that is 1 ½” deep, 12” high, and 13’ wide. Is it possible to use something like 1 ½” insulation foam board to fill this area and do a light, decorative skim coat of stucco to match the side walls?
And if so, would that also require using some sort of mesh fiberglass, nylon, or metal? I am not concerned about insulation, but rather just wanting to fill and blend that negative space to match the existing walls. I don’t have stucco experience but do have a fair amount of handyman/artistic abilities.
Thanks much for any thoughts!!
Yes, you can absolutely use foam board to fill in that space and apply a stucco finish over it. Since you’re mainly looking to create a smooth, seamless look rather than needing structural support, foam is a great lightweight option. Here’s how you can approach the project:
Steps for Applying Stucco Over Foam Board:
Prep the Existing Surface: Clean the surrounding stucco to remove any dust or debris. If the surface is very smooth, lightly rough it up with sandpaper to help adhesion.
Attach the Foam Board: Construction adhesive (like Loctite PL 300 or a similar foam-safe adhesive) is the easiest way to bond the foam to the stucco wall. Apply glue in beads along the back of the foam board and press it firmly into place. Use temporary bracing if needed until the adhesive sets.
Apply Mesh for Reinforcement: Fiberglass mesh (the type used for EIFS systems) works well here because it’s lightweight and easy to work with. Spray adhesive helps hold the mesh in place while applying the stucco. Overlap the edges of the mesh slightly onto the surrounding stucco for a smooth transition.
Apply the Stucco Skim Coat: Since this will be a thin coat, use a strongly fortified cement mix base coat with polymer additives to ensure good bonding. Apply the first coat thinly over the mesh, pressing it into the fibers for strength.
Apply The Texture: Once the first coat sets up a bit, apply a second coat to match the existing stucco texture. Feather the edges to blend seamlessly with the surrounding wall. This will take some practice to get the texture down, if you are trying to match it and practicing on drywall or cardboard is recommended first.
Additional Tips...
- If you want added durability, you can use metal lath instead of fiberglass mesh, but it may be overkill for a small, decorative application like this.
- A standard stucco base coat mix will work, but adding an acrylic fortifier will help with adhesion and flexibility, reducing the chances of cracking.
This method should give you a clean, professional-looking finish that blends well with your existing walls. Let me know if you need any clarification or alternative suggestions!
