The answer is yes, it’s very easy to add 3 1/2 or 5 1/2 inches of overhang on all 4 sides without needing any fancy rafter cuts or complicated soffit trim.
Additional materials and cost
There will be a small additional cost but not as much as you might think. The biggest expense will be additional labor.
You will need an additional 6 to 8 clean 2×4’s or 2×6’s for the overhang but you will save the same number of trim strips. And this will allow you to buy just 1 sheet of no groove siding instead of 2.
And you will need 0 to 2 more sheets of roof sheeting, depending on the size shed you are building and how carefully you plan your cuts and use your cutoffs.
You should be able to get all of your narrow roof strips out of the end cut offs on small sheds like 8×8 through 8×12.
Good value
If you’re willing to spend the extra time and labor this roof overhang is a good value. On small sheds it will be break even because you can use the cut offs from the roof sheeting and the savings in trim material will offset the additional cost of the 2×4’s or 2×6’s for the overhang.
It will improve the looks of your shed as well as being functional.
Install the small roof sheeting
See Table 2: For 3 1/3 inch overhang cut the small roof strips 2 inches wider than called for in dimension “H”.
For 5 1/2 inch overhang cut the small roof strips 4 inches wider than called for in dimension “H”.
Cut them long enough to allow 3 1/2 or 5 1/2 inches overhang on both the front and back gable ends. Remember to add 1/2 inch or so more for the thickness of the siding. For example rather than being 24/48/72 inches long it would be (24/48/72 + 4) or (24/48/72 + 6).
Install these small pieces first at the top of the trusses and be sure to space the trusses as per Step 8.
This will put a full width piece of sheeting on the bottom edge to give the overhang plenty of strength thereby eliminating the need for fancy rafter cuts or complicated soffit trim.
Install the large sheets
Install the full sheets as per Step 8 making sure everything is square.
When you are finished you will have 3 1/3 or 5 1/2 inches of unsupported overhang on all 4 sides of your shed.
Horizontal trim
See Figure 8a: Cut a 14 degree angle across the wide side of four straight and clean 2×4’s (or 2×6’s). Don’t worry about the length yet. Just use full length and cut them to fit as necessary.
Use screws: Attach them to the underside of the gable overhang with 1 inch to 1 ½ inch screws. You will not be able to hammer a nail in because it will bounce around too much (unless you have a nail gun).
You can use “C” clamps to hold the ends in place if you don’t have a helper. Attach the 2×4 trim to the front and back gable ends and then under the eaves on both sides.
Use plenty of fasteners on the ends to prevent the 2×4’s from warping and pulling away. Mark and cut the excess off the gable end trim pieces.
Now you will have a nice 3 1/2 or 5 1/2 inch overhang on all 4 sides. The 2×4/2×6 trim will give the overhang plenty of strength, give you backing to nail the shingles and drip edge into, and make the finished shed look good.Vertical trim
The 2×4 or 2×6 boards for the overhang will act as your horizontal trim so nothing else is needed there. Now you can go straight to installing the vertical trim.
Cut to fit and install the corner trim so that it fits flush with the bottom of the siding and runs up to the roof trim.
Nail with galvanized nails every 4 to 6 inches as per Step 9.