Building Recessed Roof Dormers

man with tools in an attic
What You'll Need
Plumb bob
Nails, 1 1/2 inch
Measuring tape
Circular saw
Plywood, 3ft by 4ft
Galvanized metal valleys
Staples and a stapling gun
Tool belt
Wood, 2ft by 4ft
Safety harness
Cordless drill driver
Dormer window

Roof dormers light up the interior and add living space in the attic. When turning the attic into a bedroom or other living quarters, it is important to build at least two roof dormers for ventilation and to reduce humidity. There are various styles of roof dormers, from arched to polygonal, and you can choose depending on the design needed.

Step 1 - Map the Design

Illustrate the design on a paper to estimate the size of the roof dormers and to help you in estimating the cost of your project. Visit a supplies store with the draft to get the required amount of supplies.

Step 2 - Put Your Illustration on Visible Ground

Draw the window plan on the attic floor close to where you want to make the opening. The diagram should be plumb. Insert a nail on each of the corners of the roof with the measurements you made. Make the outline of the sides using a plumb bob to direct you, and draw straight lines using a chalk. If the cut will touch the rafters, hammer a 2ft by 4ft support on the top and bottom that will be in place until you attach the new rafters on the recessed roof.

Step 3 - Prepare the Surface

ladder leaning against a roof

Prop the ladder up against the side of the roof you will be working on. Attach all the carpenter’s tools into the tool belt, and attach the safety harness to a higher ground, like a tree. Install the scaffold for support, and then get on the roof. Draw the line using the nails that extend from inside. Remove the shingle on that section, and cut out that part of the roof.

Step 4 - Create the Wall

Attach new rafters on the revealed edges. Hammer the nails six inches apart, and check the level. Have the same number of new rafters in the same position and number as the first. Lay four 2x4's on the illustration you made on the floor, and hammer the nails on all sides to form a square. Inside the square, outline the window opening, and use the measurements to cut the lumber. Fit them on the window and raise the new recessed roof wall to its place. Fit the top plate on both sides using wood to join the wall to the roof. Place the level on top of the top plate to check that it is plumb. Measure the distance from the top plate to the edge on the roof as it slants down, and mark at least six inches apart. Cut the lumber to measure, and fix the studs on that side of the wall on the marks you made.

Step 5 - Fix the Rafters

man marking a spot on a board

Attach a ridge board by measuring the distance from the end of the opening to the new wall. Place the rafters sloping from the ridge board to the top plate. Add two studs that extend from the last rafters down to the window opening.

Step 6 - Sheathe the Surface

Measure the size of the new roof and the sides, and cut out the pieces of plywood needed. Fit them on the structure, and place the waterproofing membrane on the sides where the new wall meets the old roof.

Step 7 - Final Touches

Fit the felt on top of the new roof using the adhesive. Give it a few minutes and attach the metal valley on the joint between the end of the rafters and the old roof. Place the shingles on top of the felt and fix the window in the opening.