How to Build a Slanted Shed Roof

How to Build a Slanted Shed Roof
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A slanted roof can have a considerable effect on the actual shed style. However, if you want to have a slanted shed roof, notice that one wall of your shed needs to have a different height than the other ones.

If your shed walls are all of the same height, then you will have to build up one wall. You can do it by adding plates on the top, or you can construct a small frame wall and adding it to one of the existing walls. Once you have done that, you can start constructing the roof for your shed.

However, note that constructing a roof might not always be an easy job to do. Therefore, be sure to follow this guide thoroughly, and if you are still a bit confused about something, be sure to check out My Shed Plans website. There, you will find a lot of useful information that will help you out.

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Building A Slanted Shed Roof Steps

Step 1

The first thing that you should do is measure the total span of the shed. Note that the length of your rafters will be based on the rise of the unit and a total run. Basically, it is the total span subtracted by the thickness of a wall. The best way to measure this is to hook tape to the outer side of one exterior wall and then measure it to the inner side of the opposite exterior wall.

That way, you will get the perfect measurement that you need. However, be sure that you measured it correctly, and even do a double measure if not entirely sure. It would be terrible if you measure incorrectly, even for a single inch.

Step 2

Next, you should measure the total rise of the slanted roof of the shed. If you are not a woodworker, you should know that a total rise means how many inches the roof rises per single foot. The best way to do that is to measure how much higher one wall is from the other, and then just add the thickness of the rafter. Then, subtract the seat cut and take that number in inches.

Multiply it into the total run in feet and divide by 12 (because there are 12 inches in a foot). The number you get will show you how long the rafter needs to be to span the shed from the outer side of one wall to the inner side of the other wall. This is a critical step, so be sure that you have done it correctly before moving on.

You might also want to do calculations a few times before proceeding to be sure that you have the correct measurement.

How to Build a Slanted Shed Roof

Step 3

The next thing to do is to measure and cut the rafter seats. These are notches that let rafters rest on the wall plates, and it is imperative to do the cutting properly.

At first, you should measure how long you want the overhang to be, and then mark a line, since it shows where the seat cut line must be located. Then, with a carpenter’s square, mark the outer edge of the square at the 12-inch mark for the unit run, and then mark the outer edge at the unit rise.

Put the square on a rafter with the marks that you made, flush with the edge of the rafter on your line. The unit rise mark will then be on the line and is referred to as a heel plumb line. You will notice that the heel plumb line will be parallel to the exterior wall.

Then, mark the outer edge of the square and move the square to the left until it makes the width of the shed top plate equal, and mark a line there. This is actually the seat cut line.

If all of this seems complicated, you can always check My Shed Plans website and find a perfect plan for your roof. When you open the website, you will notice that they have more than 12,000 shed plans.

Additionally, they will explain to you the easiest way to build anything that you choose, so this is definitely a website that you should check out. Also, their plans are pretty affordable and are even suited for people with absolutely no experience.

Step 4

Now, cut the other seat from your rafter. Then, measure the total run of the rafter starting from the heel plumb line, which we mentioned in the previous step. Put the carpenter’s square on the mark and repeat the last step.

Step 5

Cut the other rafters, lay them out and nail them together. You can also use block stiffeners and fillers. When it comes to overhangs, you will need to make a line where you would like them to end, then mark a cut-off point using a T-bevel.

Then, install the fascia board as well as fascia rafters. After you frame the roof, do the layout and nail plywood. Then, you will have a finished roof. However, notice that step 3 is very important and that everything should be perfectly measured.


As you may have noticed, building a slanted shed roof might not be the easiest thing to do. At first, you should pay a lot of attention to measuring. The fact is that only one, slightly incorrect measure, will lead to a wrong cut, and will, therefore, have an impact on all of the other things.

For example, if only one rafter is not cut correctly, you won’t be able to nail them together and therefore won’t be able to finish the roof.

Always do at least a double measure, and cut slowly and patiently, for the perfect results. However, if you follow our guide, building a slanted shed roof will be a lot easier. Just make sure that you followed all the steps correctly, and enjoy the work!

Shed Plans