How to Build Shed Roof Trusses

Last winter was bad for snow and ice, and my neighbor down the street had a very large, unfinished shed roof cave in. Fast forward to this fall, and my neighbor comes down to chat about how to build shed roof trusses. He decided to buy pre-made trusses from our local home reno store to save time, even though I convinced him he could do it on his own.

In this article, we’ll take a look at how to simply build solid shed roof without any fancy tools or complex math. We’ll use two different types of material, some fasteners, and a couple of power saws to get the job done.

There are a million different methods for build trusses, but I find this to be one of the most straightforward. It also negates the use of expensive hardware and extensive calculations. Take a look below for a more detailed outline of how to make trusses for shed.

Note: construct your roof trusses before erecting your shed walls!

Shed roof trusses

What is a Truss?

A truss is the timber structure that holds up your roof. They also function to keep the walls of your shed together – so they’re pretty important.

These days people seem to use the term “truss” and “rafter” interchangeably, which is inaccurate. Picture your attic. If you have large width lumber holding up your roof, and a relatively open attic, then you likely have rafters. Trusses use smaller width lumber, such as 2x4s, to create a web of triangles to hold up your roof. Just as effective, but creates less space in your attic.

If they take up more space, then why use a truss? First, they are much cheaper than rafters. Roof trusses 2x4s, whereas rafters may use 2×8, 2×10, or even 2×12 boards. A 16’ 2×12 is expensive, and if you did your entire roof structure with those, you are looking at a seriously large lumber bill. But if you are using all 2x4s, then your cost goes down exponentially.

Secondly, trusses are not difficult to make and are easy to install. They are lighter and can be prefabricated. So if you are building a shed, you just need another pair of hands and the better part of a day to install them. Installing rafters is onerous and requires much more time to install.

Common Types of Trusses Used in Sheds

There are tons of different truss designs out there, and many are used based on the span of the structure they are covering. Typically, the more complex the truss looks, the longer the span it is bridging.

For our shed, we’ll be installing a king post shed truss design, which is pretty much the simplest truss design for a shed you can build. Let’s have a look at the other truss types for a shed that you can use below.

King Post

King PostAs I just stated, we will go over how to install a king post truss system in your shed. A king post truss utilizes two top chords, a bottom chord, and a piece that connects the bottom and top chords vertically – called a king post.

Simple to make and require a small amount of lumber, king post trusses are ideal for small structures. They are only good up to 16’, as larger structures require a greater weight distribution.

Queen Post

QueenPostAlso known as a fan truss, this type of truss is just like a king post, except that it has two diagonal braces, or web runners, emanating from the bottom of the king post to the top chords on either side. They make a fan-type design, hence then name “fan truss”.

These trusses are capable of handling spans up to 22’ long. The bracing gives these trusses added strength, but also require more lumber, gussets, and time. If you are building a shed in an area that gets lots of snow, then consider this type of truss instead of a king post.

Fink

FinkAlso known as a “W” truss, this type of truss is one you’ll commonly see for sale at your local home reno store. Capable of handling up to 33’ spans, these types of trusses are found in many new home builds.

The Fink truss does not utilize a king post, but instead relies on four web runners in the shape of a “w”. While effective, they require several angle cuts and extra lumber. This would be overkill for most DIY sheds.

Howe

HoweThe Howe truss is also known as a “K truss”. It handles spans up to 36’ long. One of the differences between the Howe and Fink is the use of a king post. This makes a Howe even more complex to construct than a Fink because you are cutting 3 different lengths of web bracing, besides the top and bottom chord.

As with the Fink, a Howe truss is likely unnecessary for your shed. If you are building a large garage, workshop, or even a tiny house, then consider purchasing a pre-fab version of these trusses. You’ll save time and likely won’t spend much more than if you’d do it yourself.

Double Fan

DoubleFanA double fan truss combines elements of the Fink and single fan truss. It is a Fink truss, but with a brace between each fan.

Also capable of spanning up to 36’, this truss would require 3 different cuts to accommodate the different lengths of web bracing. This is another type of truss best left to purchase pre-fabricated.

Gambrel

GambrelA gambrel roof is a four-sided roof that people typically associate with being a barn-style roof, or something similar. A traditional gambrel roof has four sides that fit within a semicircle, or the top half of an octagon. If you are building a gambrel-roofed shed, then this is likely what you would use, coupled with a bottom chord.

However, a gambrel truss roof uses a Howe truss design beneath the top chords of the gambrel to reinforce the roof structure and extend the span.

How To Build Simple Roof Truss for Shed

Now let’s look at how to build a simple roof truss for a shed. Remember, as stated above, this process is much easier if you have your shed floor already built, but not your walls. The reason is that you can use your unfinished shed floor as a template for your trusses.

Again, for the sake of simplicity, we’ll be building a truss for a gable roof. A gable roof is your typical, two-sided roof that meets at a point in the middle. Even if you don’t know how to build a truss, any DIYer with confidence can construct a simple roof truss for a shed.

1. Determine Your Shed Roof Pitch

Calculate Roof PitchPitch is how steep you want your roof. You’ll see a roof referred to as 3:12 or 6:12, which means that for every twelve inches of horizontal run, the roof will go up 3 or 6 inches, respectively.

A run of 12:12 is a 45-degree angle. A 4:12 roof is around 19 degrees. We will be going over how to do a king post truss on a shed with a 4:12 roof, but it can be done on any type of pitch. Many building codes do not allow a roof on a shed to be less than 3:12, as flatter roofs are more prone to leaks and snow damage.

2. Choose the Right Truss Type

Take a look above to decide which type of shed trusses are right for your shed. Don’t overthink this part – a small shed only needs a king post truss. If you have a large shed or workshop, then you’re looking at a fan truss.

Now, if you have a large garage or tiny house, then I recommend a pre-fabricated Howe truss. Yes, you could make it yourself, but you’ll save time purchasing them already made. Plus, you don’t want to compromise safety just to save a couple of bucks on building shed roof trusses.

 

3. Create a Detailed Shed Roof Truss Design

Shed Roof Truss Design
Before you start cutting wood, you need to have shed truss plans with all the relevant measurements. The most important being the span of your shed, the length, and the pitch.

The span will dictate the length of the lumber you’ll need, while the length of the shed will indicate how many trusses you will need.

The span of your shed is from the outside edge of one outer wall to the other, running the width of the shed. It does not take into account any roof overhang you may, or may not, have.

An overhang is another consideration. Do you want your roof to hang over the edges of your shed? If so, by how much? Adding an extra foot will increase the amount of lumber you use and your total cost. However, an overhang can be decorative as well as functional, channeling water further away from the base of your shed.

4. Determine Roof Truss Spacing

24” on center is fine for shed trusses. If you live in an area where you get absolutely tons of snow and have a low pitched roof on your shed, then go ahead and put them 16” on center.

Homes have 24” truss spacing. However, most homes use pre-fabricated engineered trusses designed for 24” on center. Since you are building the trusses yourself, you really can’t say how much load each of your trusses can withstand.

But if you take your time and construct the truss properly, there is no reason why 24” on center spacing can’t work in your shed. If you aren’t comfortable with that, then build a few more and install them 16” apart.

5. Prepare Tools and Materials Needed

See below for the tools and materials you’ll need to complete your shed roof trusses.

Tools

  • Miter saw
  • Circular saw or jigsaw
  • Sawhorse
  • Hammer
  • Cordless drill
  • Measuring tape and speed square

Materials

  • 2x4s – not pressure treated
  • ⅝” plywood
  • Truss connector plates– 3×6
  • Nails
  • 1 ½” deck screws
  • Construction adhesive

6. Cut the Top Chords of the Truss

Now it’s time to get to work. Earlier I mentioned that building the trusses is much easier when you have a bare shed floor to work with, without any walls. You’ll see why in a second. Now that you know how steep you want your shed roof – the pitch – and how much overhang you want, you can jump right to this shed roof truss design calculator.

Before you input your values, be sure to account for the extra 4” on each side for the span of your shed. Why? Because we are going to avoid cutting notches – also known as birds mouth cuts – in our top chords. Instead, our bottom chord will rest fully on the tops of the shed walls. This allows us fewer cuts without compromising structural integrity.

Now you have your length and the angle at which you’ll cut both ends of your top chords. For this shed, our 4:12 pitch requires an angle of 18.5 degrees. Using our speed square, we’ll place the pivot point (speed square apex) at the top corner of our 2×4, lying flat on your work surface. Rotate the pivot point until the angle 18.5 on the hypotenuse of the speed square lines up with the long end of the 2×4.

Draw a line from the pivot point down across the 2×4. Use a miter saw to make this cut, turning the saw until it aligns with your mark. Now, use the same process to make the same cut on the other end of your top chord. Please note: make sure your angled cuts are parallel to each other!

7. Create a Bottom Chord

The bottom chord runs between the bottom of the two top chords. It will be exactly the length of your shed span. Use your shed base to achieve an exact measurement.

Both ends of your bottom chord will need angled cuts, but they will be perpendicular to one another, unlike the top chords. To find the angle of your bottom chord angles, simply subtract your top chord angle by 90. Then use the same method to find and mark your angles. Again, the ends of your bottom chord will be perpendicular to each other.

I use a jigsaw to make cuts my miter saw cannot. Some people prefer a circular saw, but I find the jigsaw faster and easier to handle. Whichever tool you prefer, make your angled cuts.

Now, line up your top chords and bottom on the floor of your un-walled shed. The top chords should mesh perfectly with your bottom chord. Your bottom chord should also overhang either side of the shed walls by about ½”. This is so your top chord edges don’t rub up against the shed walls.

8.Measure and Cut the King Post

Find the center of your bottom chord. Measure from there up to the bottom of where the top chords meet. Cut a 2×4 to this length – this is your king’s post.

Next, on the top of your king’s post, find the center. If your 2×4 is 3.5” wide, then it will be exactly 1.75” from the edge.

You will make an angled cut on either side of the point you just marked. It will be the same as the cut you made for your top chord – 18.5 degrees. Use your speed square with the pivot at the center mark, and rotate. You’ll find that the speed square is too big for this specific task. Alternatively, you can use the top chord cuts as a template instead.

The top of your king’s post should look like a point or an arrow. The bottom is flat and should be centered on the middle mark of your bottom chord. You are now ready to assemble the truss!

9. Cut Plywood Gussets

Now it’s time to cut your plywood trusses. Place a piece of ⅝” plywood on your sawhorses. You want your gussets to be twice the length of the stock width. So a 2×4 is just under 4” wide, so you’ll make your gussets 8” long on each side, for a total of 16” across. For height, 8” is suitable.

Outline your gusset on the plywood using a speed square. I use a piece of cardboard beneath the truss apex to outline the top part of the truss, 8” down on each side. Then I take the cardboard out from under the truss and draw a straight line across to meet either end – done! This is your template. Cut it out.

Use the cardboard template to draw an outline on the plywood. Cut the plywood using the jigsaw. Remember, you need a gusset on either side of the truss. To make things simple, you can use this gusset on the bottom of the king post and bottom chord, as well. So, for one truss, you’ll need four of this size of the gusset.

Now cut the gussets for the sides of your truss. You can use your original cardboard template, but you’ll only need half. Fold the cardboard in half, outline it on your plywood and cut. You’ll need four of these, too. Now you are all set for assembling.

10. Assemble the Shed Trusses

Lay your truss out on the floor of your shed. Align the bottom chord to the width of one end of your floor. Check the alignment and dimensions of the truss compared to the floor. Make sure the bottom chord overhangs each end by no more than ½” and that the apex of the truss lines up with the center of the shed’s width.

When attaching the plywood gussets, you’ll need construction adhesive. The stronger, the better – I use PL Premium Polyurethane Construction Adhesive. You may end up needing more than one tube. Also, I recommend nailing or screwing the 2×4 pieces together before installing gussets. Make sure you pre-drill or the 2×4 can split.

Starting with the top gusset, apply adhesive to the truss 2×4’s that will be covered by the gusset. Put the gusset over the adhesive, and use 1 ½” wood screws to attach gusset. I would use four screws per side, plus two in the king post.

Continue installing the gussets in the same manner as above. When complete, flip the truss and install the gussets on the other side.

Option: Use Steel Gussets to Assemble Trusses

Use steel gusset plates, also called truss connectors, to attach shed trusses. Before installing the connectors, I like to fasten them with 3” deck screws. This holds everything together while hammering away at the truss connectors. I also advise that you pre-drill if you choose to drive screws first, as 2x4s are prone to splitting.

It is critical that the connectors you use are load-rated. Many home reno stores carry only non-structural metal gussets or connectors. Do not use them to construct your trusses.

When you are ready to hammer your connectors in, you’ll need a scrap piece of 2×4 to put over the connector that you can hammer on. If you hammer directly onto the connector, it will get bent and not connect properly. If you have a flat piece of steel instead of wood, this works even better.

Hammer the connectors at each joint using the scrap. Make sure each connector is fully nailed into each piece of wood. Use connectors on both sides.

When connecting trusses with steel gussets to the shed, you can use Simpson H2.5A Hurricane Tie. Sometimes the steel gusset won’t fit within a connector, so I’ve given you two options to choose from – either works just fine.

Conclusion

I hope you’ve enjoyed learning how to build roof trusses for a shed. Hopefully, you’ll be able to use this guide when you tackle your next shed building project.

Remember, safety is always the most important. Never tackle truss installation without a couple of sets of helping hands.

And if you still aren’t completely sure how to build shed trusses, you can always buy pre-fabricated ones from your local home reno store. Not as fun, but much faster than building your own!

As always, please leave any feedback or comments below if you found this article helpful.

Leave a Comment