Roof framing generally falls into two types or styles. Standard American framing and trusses. Framing members for roof rafters are sized according to the height, slope and span of the roof. A small shed may be framed with two by six or two by eight rafters where a house will have two by ten and two by twelve rafter sizes.
The shallower the roof slope the larger the framing members used to carry the roof and snow loads. A flat roof roof is possible but requires the use of beams and horizontal framing to carry the roof loads. Usually a sloped roof is far more prevalent.
Standard framing will consist of multiple rafters and a ridge beam. A much quicker frame is to use a shed style framing system. This requires no ridge beam, can be installed by one person and with no ridge is less costly as well. It is desirable to obtain a four on twelve slope for your roof.
That means the roof will drop from the high side to the low side by four inches per foot of travel. If your shed is twelve foot wide, then the drop should be forty eight inches. If your slope is less than that, say three on twelve or two on twelve, you will have to use larger rafters and a product called rolled roofing in lieu of standard shingles. This helps prevent ice backup under the shingles due to the flatter roofs lesser ability to shed water quickly.
Once you have your framing completed one of the fastest roofs to install is plain plywood with rolled roofing. If you wish something more eye appealing and the ability to let light into your building, use fiberglass sheets as discussed in paragraph one. These go up quickly and once nailed into place, become a finished product. They are inexpensive and require virtually no maintenance.
Fiberglass roofing panels require a slightly different framing method than conventional roofs. In addition to the standard rafters or trusses you must install what are known as Girts. Typically two inch by four lumber they are installed in a continuing line perpendicular to the rafter framing at two foot intervals with one at the top and one at the bottom of the roof edges and two foot spaces or less in between.
The fiberglass panels will span across the girts and the girts will provide adequate places to fasten the panels. If a panel is not long enough to span the entire roof, panels may be lapped over each other and by using lap sealant, provide a very sturdy roof.
Panels are usually fastened with ring shank nails and a rubber grommets to seal nail holes from seeping in water. Screws are quite often used as well as they will not back out or loosen over time. Cost is a few dollars more but much less maintenance later on.
There are also available sponge seals for both ends of the sheets where they sit on the edge beams or plates and for any sheet laps that are made. These are very inexpensive and avoids having to custom cut some type of wooden closure strip at the sheet ends.
Another quick roof but not in my opinion as attractive, is the use of roll roofing. Roll roofing will last for many years and really requires only minimal checking to assure the lapped seams have not opened to the weather. After your framing is completed, install your plywood sheets.
If you are using twenty-four inch spacing of the rafters a minimum plywood size is 5/8 of an inch thick. 3/4 inch ply is better but costs a great a deal more. You want to minimize substrate movement to avoid cracking of the asphalt seals on the rolled roofing material. The stiffer the substrate, the less trouble you will have in the future.
If you framed at sixteen inch centers, 5/8 ply is more than sufficient. Roll roofing is applied somewhat like regular fiberglass shingles but uses far less nails and covers much roof area more quickly with each course.
Standard roll roofing is thirty or thirty-six inches wide. It is available in several colors to pick from. Warm areas pick white or light colors, Northern areas pick dark colors if you are heating the shed or garage. The dark color will help absorb the sun’s heat and aid in melting snow and providing a little free solar warmth to the roof area.
Starting at the bottom edge or eave of the roof install the starter course nailing the sheet firmly down with at both the top and bottom edges. The use of galvanized roofing nails is mandatory. Install the second sheet overlapping the lower sheet by the manufactures requirements.
Roofing is usually marked with a different colored line to show the required overlap. I have seen both four inch and six inch laps required. Note that each layer on the bottom of the sheet has an asphalt coating on the underside. Once the sun heats the sheets, this asphalt will melt and seal the joints between the two sheets.
If roofing is being installed in the winter time, roofers will use a torch to heat and seal the laps. Be very careful if you attempt to do this. Over heating the roofing can cause the roofing to melt and in the worst case, set fire to the structure below. It takes very little heat to seal the sheets so work very carefully so as not to damage them. Once done, apply roofing sealant using a caulking gun to any exposed nail heads.
On larger structures such as a full sized home, metal roofing sheets are used in lieu of fiberglass sheets. Although more expensive than conventional shingles on the outset, many companies guarantee their sheeting for fifty years or longer. Roll roofing is generally not used on homes as the appearance is not as nice looking as shingles.
One word about safety. when working on any roof make sure you always have safe and secure footing. A safety harness is always a good idea and can save you a broken leg or worse from a fall. Make sure ladders are properly secured in place as well unless you want to sit on a roof all day waiting for someone to come and stand the ladder back up. Be careful.