Framing a Roof on your Porch

So you’ve got a nice porch and you want to frame a roof on your porch it to protect it from the elements and add to its usefulness so that you can enjoy it no matter what the weather. Be advised that if you have never cut a roof before it is not the easiest project to undertake but is quite doable with a basic knowledge of carpentry and the right tools.

As far as tools go, you will need a hammer or nail gun, a set of sawhorses, a skill or miter saw, a framing square, a ladder or scaffold, and a tape measure.

The General Look

For a porch roof add-on to look right, it should mimic the look and feel of the rest of the house. This means that it should be the same pitch as your house’s roof and the shingles should match as closely as possible.

At all costs you want to avoid the “cobbled together” look. The goal is not only functionality but also to protect the value of your property. Does your existing roof have a hip roof? A hip roof is extremely strong and assists in locking the walls together.

How extensive is the roof overhang on your house? Fourteen inches? Sixteen inches? Measure it and plan to make the porch roof overhang match it.

The Layout

Where you start depends on your home’s configuration but in general this is the procedure to follow. First set the end or gable porch truss flush against the porch’s end wall's top plate. Now, start working your way back in the direction of the house, all the while setting the trusses and bracing them together.

After the closest truss to the house is in place and securely nailed, stretch a string line on the level from its peak right to the roof line peak. Now this is where you want to nail the ridge board to the roof.

On both sides, set a valley rafter beginning at the ridge board at your house roof’s point down to your porch truss. Secure jack rafters that are perpendicular to your ridge board down to your valley rafter. The spacing will depend on your local building code. Generally this will be on sixteen inch centers.

Almost all roof designs designate an overhang on the gable end to shield the end wall from rain and snow. Commonly, most overhangs will extend one or two feet, but you will duplicate your house's overhang. As mentioned above, fourteen to sixteen inches is common.

Wrapping It Up

Next you will proceed with the normal roof finishing techniques. First install the sheathing. You will want find out the thickness of the sheathing on your main roof so that you can use the same methods on the porch.

Save yourself some trouble by measuring out your sheets prior hefting them onto the porch roof. Make sure to space your sheet ends at the center points of the truss rafters so that adjoining sheets will share a common nailing surface. Now roll out felt from left to right. Make the first run at the bottom and overlap each run by about six inches.

Be certain to add metal flashing in your roof’s valleys and right along the roof’s lowest edges. This is to safeguard against water. Finally, nail on your shingles matching the ones on your house’s roof. As with the felt, start at the bottom and work your way up.

Now is the time to paint any exposed wood to match your house. When applying your shingles, you will find that the most economical method is to use a staple gun. It would behoove you not to take this approach. In high wind conditions staples lack the holding power of nail heads. Especially on a small porch addition, the extra time to use nails is justified.