How to Build Roof Dormers

Tips for Building Roof Dormers

Introduction:

So you bought an older house that has limited window space in the upstairs or you want to turn a large attic into additional living space. This can be accomplished by building a roof dormer. A roof dormer can add to the look of your house as well as provide the window space in the upstairs that is otherwise dark. Building a roof dormer can be a DIY project if you have a reasonable amount of carpenter experience. Building a roof dormer requires several carpenter skills that include the basic construction of framing as well roofing.

Before deciding on a roof dormer, consider what you want for a completed project. Do you want a small dormer or two in the front of the house or do you want a shed dormer in the back of the house. Keep in mind that you want the final outcome to be in balance with the rest of the house and meet you objective. Also consider skylights as opposed to dormers. Installing skylights involves less work and can most likely meet you requirements.

In nearly all cases you can add a dormer to any existing roof. The complexity of the task depends on how your home was constructed. If it has traditional roof rafters and an open attic you should have no difficulty adding a dormer that you can install a window. If your home was constructed with roof trusses you can still install a dormer although the task becomes a little more difficult. In both cases you can cut into roof rafters or trusses and modify them to make a make the dormer.

Tips for Building a Dormer

Before starting this task, drawn a detailed building plan to scale. Don’t make the dormer too small or too large. You can get a feel for this by looking at houses that have dormers that appeal to you. Nothing will look worse than an undersized or oversized dormer for the roof size.
The first step is stripping off the roofing material in the area where the dormer is going to be constructed. Before beginning, ensure that you have the necessary tarps to cover the area in the event it rains.
If you’re building a dormer on a roof framed with common rafters you’ll need to double or even triple the rafters on either side of where the dormer will be built. This will transfer the roof load to the rafters on either side of the open space.
Start to build the dormer by constructing the three walls that make up the front and sides of the dormer. Once the walls are in place, construct the roof to accommodate the slope of the existing roof and the dormer.
Install roof flashing down the full length of the base on each side of the dormer and across the front. I highly recommend installing a generous amount of rain guard before installing the flashing to make it completely waterproof.
Install the roofing shingle being careful to completely tie the new shingles into the existing shingles.

Now that you have completed building the roof dormer it’s time to install the window (s) and complete the inside.

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