Some time ago I received a question from one of the readers asking how to finish the top edge of a shed roof. Finishing the top edge of a standard, single sloping shed roof is different from other roof types such as gable or gambrel. Using the appropriate type of shingles and installing them to maximize water resistance is critical when applying the top row.
So how to finish the top edge of a shed roof? Installation follows the same principles as the other rows of shingles, using either three-tab or architectural shingles. However, there are a few key differences. Here’s how to shingle the top edge of your shed roof:
- For the final row, cut shingles into strips
- Ensure strips are wide enough to cover nails
- Install your strips
- Apply sealant over exposed nails on the last strip
- Use more sealant along the top edges of all shingle strips.
In this guide, we’ll take a look at how to properly lay and install your final row of shingles for a single slope and lean-to style shed roof.
How to Finish the Top Edge of a Shed Roof
Shed roofs come in all shapes and sizes, but we are looking specifically at two types: single slope and lean-to. Later on, we’ll investigate the finer points of applying shingles to the top row of a lean-to type shed. Remember, a lean-to shed is just that – a lean-to! It leans against another structure, like your house, garage, or another shed.
Right now, let’s look at a regular, single sloping shed roof. Finishing the last row of your shingles isn’t as easy as throwing one last course of shingles on and calling it a day.
You could, but you would have tons of exposed nails, which is a recipe for leaks. Instead, you are going to cut your three-tab or architectural shingles into strips to minimize the number of exposed nails.
Below is how to install the last row of shingles on a standard shed roof. This method will ensure your shed is completely weatherproof.
Tools and Materials
- 1 ¼” galvanized roofing nails
- Shingles, cut into strips
- Roofing utility blade
Your last course of shingles should come as close to the top as possible. If you have overlap, that’s fine. You’ll use your utility knife to trim the edge so that it is flush with the top edge of the roof. If the adhesive strip of the shingles is beyond the top edge, then avoid laying another row.
Cut your shingles into strips. Each strip should be wide enough that, when placed perpendicular along the top edge of your shed roof, it covers the nails of the previous course of shingles.
Lay your first shingle strip so that it is flush to the rake end and covers any exposed nails of the shingles below. An overhang of about 1 ½” beyond the top edge is ideal.
Nail each shingle strip so that it overlaps the nails of the previous shingle. Remember, you are laying these in a perpendicular fashion so that the adhesive strip points towards the top edge of the shed.
When you get to the other edge, you will have one shingle strip with exposed nails. Nail the shingle with four nails – two in the adhesive stirp and two at either corner.
Use bitumen-based roofing cement to cover each nail head. Trim the edges on the rake and top edge so that they are flush with the other shingles.
Apply the same roofing cement to the edges of the shingles along the top edge. You will apply the cement to the parts of the shingles that are exposed.
When installing your last row of shingles, we are basing this on the assumption that you’ve already installed your drip edge. However, there is a better solution for finishing the top layer of shingles on your shed roof and it involves putting on your top edge drip edge over the next-to-last layer of shingles.
If you’ve already put your drip edge on the top edge of your shed, then don’t move it. Adding more nail holes to a finished roof is not recommended. The method described above is an excellent way to finish your shed roof.
On the other hand, if you have not yet completed your shed roof, then consider this method as a sturdier alternative to typical top row shingle installation.
- See step 1, above. Your goal is to get your last row of shingles as close to the top edge as possible while keeping the adhesive strip on the surface of the roof. If the strip is beyond the edge, then there is not enough room for another course of shingles.
- Install drip edge so that the top lip goes over the last course of shingles. Nail drip edge accordingly. Before you install the drip edge, be sure the shingles are flush with the top edge. Otherwise, the drip edge will not sit properly against the top edge fascia board.
- Continue shingling as you did in the manner described above, with your shingle strips.
- After you seal your last four nails with roofing cement, you will not need to seal along the top edges of the shingles as you did above. Since the drip edge goes over the previous course of shingles, any water that goes under the shingle strips will be directed to the other shingles, below.
This method reduces the need for roofing cement along the entirety of the top edge and gives water an improved path down the surface of the roof. High winds and heavy rain could potentially get under the top layer of shingles.
While roofing felt provides a last line of defense, it is better to keep water off it altogether. A drip edge that goes over the shingles ensures felt will not be exposed to water via the top edge.
How to Finish the Lean To Roof Leading Edge
A lean-to shed leans up against another structure. Waterproofing on type of shed is important, but it is doubly important with a lean-to style shed.
Water that infiltrates a lean-to style shed not only risks the integrity of the lean-to but also the structure it leans against. Thus, ensuring a watertight connection between the lean-to roof and the other structure is critical.
Unlike a stand-alone shed, finishing the top row of shingles on a lean-to does not involve cutting strips. However, you will need a couple of different types of sealers to ensure screws and gaps are not exposed.
Here’s how to shingle the last row of a lean-to roof:
Install your shingles to the top edge of your lean-to roof. Ideally, the top edge of the last shingle row is flush with the top edge. If there is only a little space left, then you’re fine and don’t have to lay another row yet.
If the gap allows you to put another course of shingles, then do it. You may have to trim some off the back to allow it to fit flush against the top edge, which is fine as long as the adhesive strip is still there.
You now have a final row of shingles with lots of exposed nails. These must be covered. Instead of using roofing cement, you will run a final course of shingles.
Overlap the final course of shingles, being sure to stagger them just as you would your other shingle rows. Make sure the last course completely covers the nails of the previous row.
When nailing the final course, make sure you nail as close to the top of the edge as possible. Be careful that you are still nailing into the roof sheathing and not the fascia board.
Cover the nail heads with roofing cement.
Use a heavy-duty exterior thermoplastic sealant to seal the gap between the top edge of the shingles and the adjacent structure.
The most important part of this procedure is installing the thermoplastic sealant. Water that gets between the two structures can damage two buildings at once, so you want to ensure no space is left unsealed.
Making sure your last row of shingles is flush against the other structure makes using the sealant easier, the gap smaller, and will result in a better connection between the two structures.
Sometimes sealant is not the best option when covering the gap between the lean-to and main structure. The sealant can crack or peel, particularly if regularly exposed to direct sunlight.
Using aluminum flashing as a “connector” between the lean-to and adjacent structure is an even better way to waterproof the roof of your shed and the adjoining wall.
Although this solution is more likely to produce a solid, long-term result, it does require a little more work than simply applying sealant along the top edge. Here’s how to use flashing along the top edge of a lean-to shed when finishing the top row of shingles.
- Remove sections of siding immediately adjacent to the top edge of the roof. If the siding is vinyl, use a siding removal tool to pop out the bottom edge.
- Finish the shingles up to the top edge of the lean-to as described in steps 1-5, above.
- Using a coil of aluminum flashing like this, cut a length that will run the length of your top edge, with an extra inch on either side.
- Bend the length of flashing in half. A piece of lumber the length, or longer, of the flashing clamped with three or four quick clamps, will allow you to bend the piece in half quickly.
- Install the flashing first against the wall of the adjoining structure. Use the same galvanized roofing nails you use for your drip edge. Be sure to nail flashing into studs wherever possible.
- Flashing goes under any house wrap you have beneath the siding.
- Once flashing is secure against the wall, you can re-install the siding and house wrap. Let the sections of vinyl lay flat against the lean-to roof. You may have to trim some of the siding to have to rest flush.
- You do not need to nail the flashing to the roof of the lean-to. Ensure that the width of the flashing is such that it covers all the nail holes of the last row of shingles.
Depending on the type of siding you have, it might not be possible to utilize this method. Any vertical siding, whether wood, aluminum, or vinyl, would make cutting and getting under the siding much more difficult. In those instances, the original method for completing the last row of shingles on a lean-to shed is recommended.
However, if you have regular vinyl siding, this method can drastically improve the water-resistance of your shed. Flashing guarantees no exposed nails or roofing cement, which are typically entry points for moisture in a shed roof structure.
Installing a shed roof that is impermeable to the elements is not easy, and the top row of your shingles is often the most vulnerable to water. Following the above steps to finish the roof of your lean-to or single-slope shed will help you keep your shed dry for many years.
As always, I hope you found this guide helpful and it helps you successfully install the top row of shingles on your next shed roof project. If you have any questions, concerns, or comments, please feel free to leave some feedback, below.