How to build a garage from the ground up Roofing is fun and easy

How to build a garage from the ground up Roofing is fun and easy

Step 12: Roofing is fun and easy

Roofing IS fun AND easy, as long as you are watching someone else do it. But having come this far, there is no reason to quail at the prospect of falling to an ignominious end while trying to catch a sliding hammer. In the following sketches, the sheathing is not shown on the structure because I was too lazy to draw it, your garage should be sheathed before roofing. Get to it!

A word about roof pitch. Premade trusses and roofs in general are rated by their rise over a fixed distance, usually 12 feet. So a 5/12 pitch means that for every 12 feet of horizontal travel, the roof will rise 5 feet. Many older homes, like mine, have a pitch that is closer to 10/12. Let me tell you that unless you are a planning a loft over the garage or are a huge stickler for detail and want your new garage to match the pitch of the existing house, then do yourself a favor and go with a lower pitch. Additionally, local building codes often limit the height of accessory structures and a steeper pitch can push you over the limit so that you will need to secure a variance permit which will require approval by people who don’t like to give variances. I thought I was being smart by choosing 5/12 over the more standard 4/12 in order to gain a few more inches of storage space, and by the end of the job I cursed my incompetence and inexperience roundly. It turns out that right below 5/12 is the slope that shingles and other objects will stay put on a slanted surface covered in roofing felt. So unless you like making frantic grabs for stuff that is sliding inexorably down the roof like Lando into the maw of the Sarlacc then I suggest you opt for a modest 4/12 roof. This advice would have been helpful during the planning and purchasing phase, but like those tests where the first instruction is to read all the instructions sometimes the devil is in the details. Muhahahaha!

OK, before we begin roofing, you will need to switch your tool belt to the "roofing’ configuration pictured below. The key differences are that now you only need roofing nails and staples, you will want to switch blade styles in your utility knife, and it can be helpful to have a cat’s paw for removing nails without damaging shingles. Contrary to the photo, it is helpful to have two utility knives for roofing, one with a standard straight blade for cutting roofing felt and a hook blade for cutting shingles. Another note, I only had a framing nailer for my project and shingled by hand. Hammering the roofing nails by hand is not too bad since the nails have a big head, are shorter, and not that many nails are used. You may want to track down a roofing nailer however, especially if it is really hot out. Surprisingly, a black felt covered roof is not top on any lists of summertime hang out spots.

With the garage below fully framed and sheathed, the roof sheathed, and the eaves and truss tails trimmed, we can begin on covering the roof. The first step is to get your D-style drip edge and haul it up on the roof. Using the 1 1/4" roofing nails, you want to nail this drip edge all around the edge of the roof. Use nails every 12-16" or so. Cut the metal drip edge to length with a pair of tin snips, which will also come in handy when installing vinyl siding. On the slanted gable ends, be sure that the sloping drip edge overlays the horizontal drip edge so that water does not get channeled under the drip edge and cause rot. Also, if you plan on putting gutters on your garage, then you will want to use a different drip edge style on the lower, horizontal edges. This is called gutter flashing or fascia or something. You will find it in the same place as the regular drip edge at your local building supply center.

How to build a garage from the ground up Roofing is fun and easy

After the edging is installed all around, get a broom and sweep the roof to remove any sawdust, nails, or other junk. This helps the ice and water barrier stick to the roof deck, improves traction, and protects the roofing felt from damage. Then you want to unbox your ice and water barrier and install it along the lower edge of the horizontal sides of the roof. Strictly speaking this ice and water barrier is only really needed if you heat your garage and you live in a cold climate with snow. Heat escaping through the roof melts snow which runs down to the eaves which are cold and refreezes the water. A dam forms and water builds up and can penetrate the roofing material. The membrane seals nail punctures and prevents water infiltration. If you live in a snowy climate this barrier is cheap insurance against water damage so I installed it anyway even though I don’t plan on heating the garage. Peel the protective backing off the barrier as you go. It helps to have two people. You can pop a few staples through along the way to help hold it in place as you press the sticky side down to the roof. Working this close to the edge may be easier for you from a ladder. You want the ice and water barrier to stick to the drip edge but not completely overlay it. Repeat the installation on the other side of the roof. It is OK to have a seam in the barrier, overlap cut edges by a foot or so and press the adhesive down firmly. Take care when installing to avoid air bubbles.

Next get the rolls of 15# black roofing felt (AKA tar paper) and start rolling it out parallel to the ice and water barrier. You should overlap the horizontal seams by a good 6" inches, do not make any vertical seams if at all possible. Cut the roofing felt with a utility knife and make sure that it overlays the drip edge somewhat but doesn’t hang all the way out beyond it. Roofing felt is cheap so don’t be shy. It should be noted that all seams in your roof should be made such that the uphill layer is on top of the downhill layer. Use a hammer tacker or stapler to staple the roofing felt to the roof. When tacking the sheets in place, measure to make the roofing felt layers are as horizontal and parallel as possible. If you do so, then the lines printed on the paper can be used for guiding shingle placement. Continue laying layers of roofing felt up the roof until you reach the peak. Since we are using a ridge vent, we want to trim the felt so that it does not obscure the slot for ventilation. If you have any protrusions in your roof for lavatory vent stacks, chimneys, etc you will have to cut holes in the roofing felt for them as well as do any needed flashing. I’ll let you figure that out, because you should have planned a hole-free roof. Repeat the process on the other side of the roof.

With the roof felted, it will withstand some light rain in a pinch but the best plan is to push through the whole roofing project in a single sprint if at all possible. See the sketches below for clarification on the layers involved in the roofing.

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