A Rotten Window

The window in this second floor bedroom developed a water leak that led to significant wood rot in the window and structural members surround the window. The leak first manifest itself with rain water coming down the inside of the window below the second floor. At least 3 years ago a hole developed in the soffit below and to the right of the window. The previous homeowner patched the hole with drywall mesh tape and drywall compound, followed by paint. This disguised the problem but did not resolve the issue. Extensive caulk was applied to the window sill and brick mold, but no repairs were made to rotten material already beginning to show.


Three months ago, following an extended period of heavy rains, the soffit patch failed and fell to the porch floor. At the same time the water that had flowed down the first window stopped. I was called to repair the soffit and any other damage that might have occurred due to leaky window.

On initial inspection, the brick mold on both sides of the window, the window nosing, both sashes, and the window frame had rotten areas. The sill plate and left leg of the window frame had rot perforation. The left and right legs and bottom rail of each sash had significant wood rot. By examining the hole in the soffit I could also determine that there was some wood rot in the rim joist between the first and second floors. I could not determine the extent of the structural rot until I opened the wall.

After the home owners gave approval to begin, I removed the casing from the interior of the window and cut out a portion of the drywall immediately below the window. This revealed that the jack studs, window sill 2x4, bottom wall plate, and the cripples had significant rot in them. The 2x4 window sill was soaked, even though it had not rained in the previous three weeks.

To make the repair, the entire window needed to be removed from the opening and the decorative 2x6 cedar boards picture framing the window had to be removed. The 2x6 decorative board covering the rim joist was also removed, and the remaining portion of soffit was cut out. This revealed that the OSB sheathing material below and to the right of the window were completely rotten. After consulting with a stucco repair contractor, it was determined that the stucco to the right and below the window needed to be removed and new sheathing applied.

The wall was opened up. The framing under the window was replaced. The subfloor immediately under the wall framing had rotted, but the floor joists and top plates from the first floor showed no evidence of rot or water damage. A new rim joist was set in place, and the wall was covered with OSB and 15# roofing felt in preparations for new stucco to be added. New decorative cedar 2x6's were installed replacing the old ones that also had evidence of wood rot. All 4 sides of the new decorative cedar members were painted with exterior primer before installation. New fiberglass insulation was installed in the wall cavities under the window, covered with 6 mil poly vapor barrier, consistent with the rest of the house. The drywall removed earlier was returned and the interior was prepared for painting.

Because of the extent of the wood rot in the frame of the window and in the sash frames, new members had to be used. The original frame of the window had the exact dimensions of exterior door jamb material. This was used to replace the sill from both sides of the window and to replace the left leg of the window frame. Because the material was already primed on all surfaces, the portion of the frame that would be inside the house was sanded to bare wood in preparation for stain and varnish.

Three of the four sides of each sash frame had substantial rot. Rather than salvaging the top member and replacing only three sides of the sash frame, a whole new sash frame was fabricated from cypress wood, known for its excellent resistance to wood rot. The old sash frames were used as models and the cypress was machined to match the dimensions exactly. The exterior, mortise and tenon ends, and the channel for the insulated glass unit (IGU) were primed, and the interior side was stained and varnished. During assembly, the IGU was caulked into the new frames, and the mortise and tenon joints were caulked. After assembly, finish paint was applied.

After completion of the repairs to the window frame and sashes, a new sill complete with nosing was fabricated, primed, and attached to the sill of the window frame. The unit was returned to the window opening, shimmed and centered so the interior and exterior trim would fit perfectly with its previous installation. In this way the paint lines on the inside would match perfectly. The gaps around the window frame were filled with "Great Stuff" insulating foam. The exterior was trimmed out with PVC brick mold and caulked in.

After the exterior was completed with new trim, caulk, and stucco, paint was applied. The stucco paint was applied to the patch and the rest of the stucco surround the window. The decorative trim and window were painted with the same material that was used the last time the house was painted.