Fixing water damage and structure in Dormer

Fixing water damage and structure in Dormer

Originally, a built-in bookcase was situated on the landing between the main main level and second floor of our house which was part of a dormer structure. While it was not in the best shape, with a little cosmetic work we thought it would be the perfect place to keep our family photo albums.

book case
The built-in book case under the window hid the water damage.

However, as the demolition of the second floor progressed due to the insulation issue, I decided to rip out the bookcase and build another one later. As I proceeded with the removal, I discovered the drywall behind was severely damaged due to a water issue.


water damage
The water damaged framing that was hidden behind the drywall and book case.

The water infiltration could have come from two possible sources. The eaves trough had been nailed directly to the siding (there was no fascia board) and water came in through the nail holes. I had witnessed this during a particularly heavy rainfall. When the roof and eaves troughs were replaced, I had a fascia board installed to solve this issue. The other source of leaking could have been from the old window, an issue that should have been solved after we had a replacement window installed. As I was demolishing the bookcase, siding was being installed on the exterior of the dormer so I was confident that any water infiltration was a thing of the past, though I would find out later that it was not..  However, I still had to deal with the damage that had already been done.

The two horizontal 2 x 4’s were the top plate of the main floor structure and the bottom plate of the dormer structure. They were so severely rotted that I was able to crumble them with one hand with very little effort. The studs were also significantly damaged.

The “mickey mouse” fix

I attached a 2×4 across the studs and propped it up with a 3 or four other 2 x 4’s supported by the floor of the landing (not shown).  I then surgically removed all the damaged portions of the top plate and the studs.  The new top plate in this area is somewhat lower than the original so that it could be securely fastened to 4×4 posts on either side of the landing area using Simpson Strong Ties.  The studs were sistered and toe screwed to the new top plate.  The sheathing was reattached to the new structure from the inside using L-brackets (also by Simpson).

dormer wall

I was fortunate that all the damaged wood was easily accessible once the wall was opened up.  The rest of the dormer is part of the bedroom and the top plate supports the floor joists.  That repair would have been truly nightmarish.

Serious problems with the window structure

I was concentrating so much on replacing the rotted wood that I missed another obvious problem.  At some point in this house’s past, the original windows in the dormer were replaced with larger windows, but the installer did not properly modify the structure.  Instead, he had just cut a larger opening and slapped the window in place.


You can see how the studs had been cut to accommodate the window, but without a proper header supported by jack studs, the window is actually supporting some of the weight of the roof.

The repair I had done may have been adequate for replacing the existing structure, but it did not address the lack of structure around the window. I decided it was time to call in a professional contractor who had the experience and confidence to properly fix the dormer.


Proper structure for window and door openings

Graphic courtesy of Used with permission.
Graphic courtesy of Used with permission.

The header transfers the weight of the structure above the opening to the jack studs which are reinforced by the king studs. The size of the header depends on the size of the span and the weight it supports.

The Proper Fix

window framedThe window was removed and set aside.  The 2×4 studs that were completely in this area were removed.  The other studs were cut off at floor level.

A 2×6 bottom plate was installed, supported both by the studs and the floor of the landing.  Next, the 2×6 top plate was added to the existing top plate.  Then the new studs were installed.  The header over the window, comprising of 2 2×8’s with OSB sandwiched in between as a spacer, came next, followed by the sill and remaining studs.  What was once a mish-mash of sloppy or questionable workmanship (including my own) is now a strong and sturdy structure.   As an added bonus, we took the opportunity to move the window over so that it is now centered in the landing area.

Structural Repairs: How to “unbutcher” a house

The Back Dormer: Repairing water damage and fixing framing problems
The Back Dormer:  Adding ventilation and eliminating water leaks
The Sunken Tub
Supporting a house from the basement up
Load-bearing walls