Adding a dormer can brighten up small attic room

Dear James: I use my dark attic just for storage, but the underside of the gable roof is low. I think adding a dormer would help a lot in the area. What is a good plan to build one for my home? — Steph T.

Dear Steph: In addition to providing more headroom, dormers can provide much additional natural light in an attic so you won’t need electric lights. I recommend installing a minimum of two, because it looks more balanced from the street. Making two of everything is not much more work.

With a gable roof, a small doghouse dormer is an easy-to-make design. It is called “doghouse” because it looks much like a small doghouse. Attics are meant to have ventilation, so your dormers do not have to be airtight. Your main concern is to make them and their seams to the existing roof watertight. A leak can ruin the attic floor insulation.

The first design concern is the size of the dormer. This depends primarily on the vertical height of your roof from the gutter to its peak.

In northern climates, roofs have a higher pitch for snow loads than roofs in southern climates do, so almost any size works. In either climate, a larger house will have a greater vertical height.

If possible, there should be at least 1 foot of space from the peak of the dormer roof to the house roof and 1 foot from its bottom to the lower edge of the house roof. This simplifies installation and allows adequate room for flashing to eliminate water leaks. It also looks much better with some space at the top and bottom.

Another size factor to consider is the size of the windows you want to install. In general, for aesthetic reasons, the dormer windows should be smaller than the size of the windows on the floor below them.

Check at your local home center store to see if they have some custom windows, close to the size you want, that the buyer did not end up buying. These are usually priced at a steep discount.

Once you have selected your dormer windows, this will determine the height and width of the front face of the dormer.

Now you have to determine the pitch of the dormer roof, which allows for the 1-foot clearance under the house roof peak. If there is adequate clearance, making the dormer roof the same pitch as the house roof looks best.

It is not difficult to build much of a dormer yourself. Most of the work can be done on the ground or inside the attic if there is enough headroom. Unless you are experienced and comfortable working on top of a roof, have a professional remodeler do the final installation and finish work.

The most critical measurement when building a dormer is the pitch of the house roof. The best method to measure the house roof pitch is from inside the attic. Select a point on the top of a rafter and measure the run (horizontal) distance and the rise (vertical) distance to the peak.

Use this exact pitch when building the sloped sidewall of the dormers. The rest of the construction is similar to building a mini framed house.

Have a question for the author? Send your questions to Here’s How, 6906 Royalgreen Dr., Cincinnati, OH 45244, or visit www.dulley.com.