You’re in the middle of a build and it’s time to begin framing your shed roof. You know there are a variety of ways how to attach rafters and trusses to the top plate, but you aren’t sure which is best for your project.
What is the best way to attach rafters and trusses to a top plate? Several methods can be used to accomplish this job, including toenailing, hurricane ties, and even screws. In this article, we’ll review each method to help you determine which works best for the roof you’re building.
- What Are Trusses And Rafters?
- How to Attach Rafters to Top Plate
- How to Attach Roof Trusses to Top Plate
What Are Trusses And Rafters?
Both trusses and rafters can be used to create the roof of a building. While they function similarly, they have unique differences that affect how they attach to the supporting walls.
Let’s begin by comparing these two different roof styles. Rafters are beams that run from the peak of the roof to the top plate of the supporting walls. They join at the peak of the roof by connecting to the opposing rafter or to a ridge beam that runs the length of the peak of the house or shed. Rafters are installed piece-by-piece during the construction of the roof.
Trusses, like rafters, form the profile of the structure’s roof. However, unlike rafters, trusses are pre-assembled before being installed. Trusses consist of two lengths of lumber that create the upper edge of the truss, a bottom chord that connects the two opposite ends of the top chord, and a series of supporting webwork in the middle.
Trusses are usually assembled in a warehouse and then installed as one piece. Due to the additional supporting members, trusses are typically much stronger than rafters and can, therefore, handle longer spans.
For more information on trusses and rafters, check out my article on rafters vs. trusses.
Before we get started, it’s important to consider why attaching your roof, be it a truss-style or rafter-style roof, to your structure is such a critical step in the construction process. It’s important to understand that not all the methods we will discuss in this article are equal.
Some methods can handle greater uplift loads. What’s uplift? Uplift is the pressure created when the wind blows upwards on the roof of your structure. During some natural disasters such as tornadoes and hurricanes, the amount of uplift your roof can handle might determine whether the roof stays on or not.
While this article won’t go into great detail about all the factors that go into determining the upload rating of a roof, which includes everything from the span of your roof to the type of lumber you use, we will discuss which attachment methods are stronger than others.
When determining what’s right for your roof, consider where you live and what weather conditions your building will need to withstand. Certainly, if you live in a coastal region that is subject to hurricane activity, you should use hurricane ties.
How to Attach Rafters to Top Plate
It’s essential to have a solid connection between a rafter and a top plate to ensure that your roof is stable. The gravitational forces on a roof cause the rafters to want to push outward. As such, it’s important to have rafters properly secured, so these forces don’t win out.
Part of this has to do with creating a birdsmouth cut to facilitate the joining of top plate and rafter. A birdsmouth cut involves taking a notch, shaped like a bird’s mouth, out of each rafter where it meets the top plate.
This notch allows the beam to rest flush onto the top plate. Is it necessary? While you may be tempted to avoid the admittedly tedious process of making birdsmouth cuts in each rafter, don’t do it.
First of all, the notch creates more surface area in the connection between the top plate and rafter, allowing for a better connection for fastening the two together.
There’s also gravity to think about. Those gravitational forces we mentioned earlier are pushing outward on each rafter, from peak to eave. By cutting a birdsmouth notch, those forces are redirected downward onto the wall plate and wall, which is exactly where you want those forces to go.
After all, it’s the job of the walls to hold the roof up. This prevents the rafter from potentially shifting, causing your roof to sag, or worse, collapse inward.
For similar reasons, you should also consider using collar ties if you plan on using rafters. A collar tie is a length of lumber that attaches to each opposing rafter near the peak, preventing your rafters from spreading apart. Collar ties also take the stress off of your wall plate and rafter joint.
For additional support, you can use ceiling joists, which are lengths of lumber that run from the end of one rafter to another.
Toenailing is one of the time-honored ways of securing your rafter to your top plate. It involves attaching the rafter to the top plate by driving nails through the rafter and into the wall cap at an angle on opposing sides of the rafter. This method is used because it simply isn’t possible to drive straight through the plate into the rafter because of the wall studs.
How many nails you should use depends on the size of the top plate. For a 2×4 top plate, use three toenails, alternating sides. For a 2×6 top plate, use five toenails, again alternating sides with each nail.
Using an 8d nail, drive each nail in at about a 30-degree angle with a distance from the joint so that about 1/3 of the nail length goes into the rafter and the remaining 2/3 into the wall cap.
These are commonly called “slant-driven” nails. What’s the point of this?
The slant driven nails on opposite sides prevent the nails from being pulled out. It also makes the nails less likely to be sheared off by the weight of the roof.
2. Hurricane Tie
Not interested in fooling around with toenailing that involves estimating angles and depths? Want a more secure joint. Then spring for Simpson Strong-Tie Hurricane ties.These ties, which look similar to deck joist hangers, consist of a metal plate that cradles your rafter while butting up against the wall plate. As with a deck joist hanger, there are designated nail holes, making the installation process somewhat foolproof.
Once your rafter is in place, slide the plate into place and attach with Simpson Strong-Tie structural screws or galvanized 8d nails.
Simpson Strong-Tie also offers another style, which attaches to the front of the top plate and the side of the rafter. As with the other style, these connectors offer convenience as well as strength. Line them up and drive your structural screws into each of the ten predrilled holes.
As the name implies, these ties are designed to keep your roof firmly in place in high winds or even an earthquake. Although you’ll pay a little more for these, it’s worth the convenience and added strength you get.
3. Ridge Rafter Connector
As the name suggests, these handy connectors are typically used to attach rafters to the ridge beam at the peak of your roof. They work just as well to connect rafters to top plates. They work especially well with a lean-to shed.
These connectors attach to the lip of the top plate with galvanized nails through predrilled holes. The rafter is then inserted into the bracket that is attached to the plate and secured with nails via predrilled holes.
4. Attaching Rafters Without Birdsmouth – Variable Pitch Connector
If you’re really against the idea of cutting birdsmouth notches into your rafters, then you might consider Simpson Strong Tie’s variable pitch connectors. The connector attaches to the top of the wall plate and includes an adjustable bracket that accepts and secures the rafter.
This bracket will adjust to accommodate slopes ranging from 3:12 to 12:12.
With this bracket, you eliminate the need for notches and toenailing. Just install the bracket and install it via predrilled holes with 10d nails. This variable pitch connector can save you a lot of time, but it won’t save you money as these brackets don’t come cheap. Decide if the time saving is worth the added cost when considering this option.
5. Special 6” Screws – TimberLOK
Toenailing is typically used when it’s impossible to nail through the top plate into the rafter. Well, TimberLOK has another option. You may not be able to nail through the top plate into the rafter. But you can drive a screw through it.TimberLOK 6-inch long screws secure your rafter to the top plate by driving a screw at an angle from the joint between the wall stud and top plate, through the top plate and into the rafter. Is this strong enough? Rest assured it is. TimberLOK’s screws meet the IRC 2012 national code requirements for rafter or truss to top plate connections.
Requiring only a single screw per rafter, this presents one of the fastest ways to join your top plate and rafter. A TimberLOK screw doesn’t even need a pilot hole.
How to Attach Roof Trusses to Top Plate
Although many of the attachment methods for trusses are the same as rafters, attaching a roof truss to the top plate is a little more complicated due to the nature of trusses.
Unlike rafters, which are installed piece by piece, trusses are installed after they have been completely assembled. This means lifting and placing an object that can weigh hundreds of pounds depending on the size of the roof you are constructing.
For homes, trusses must be lifted into place using a crane. For sheds, trusses are typically light enough to maneuver into place by hand, but you will likely need a couple of extra sets of hands to accomplish this task.
Because the bottom of the truss is held together with a bottom cord, no birdsmouth cut is required for attaching the truss to the top plate. The bottom cord should rest squarely onto the top plate, making attaching the truss a comparatively simple process.
To make this connection, keep in mind that, as with rafters, most building codes require hurricane tie brackets to protect your roof against high winds. Whether hurricane ties are required is largely dependent upon where you live, so make sure to check your building code to see if this is necessary.
Even if they aren’t required, it’s best practice to use hurricane ties to ensure your structure is properly protected.
The general rule of thumb for truss installation is that you’ll need to install one at least every 24”. With that in mind, determine the space from end to end and space your trusses evenly. After attaching your truss, make sure it is plumb before proceeding to the second one.
Use bracing to keep the trusses in place as you work your way across.
As with rafter-style roofs, toenailing is one of the most common ways of attaching a truss-style roof to a wall plate. Toenail a truss into the top of the wall plate by nailing through the sides of the bottom chord at a 30-degree angle.
Given that this section of the bottom chord is likely where one of the connector plates that hold the truss together is located, you may need to nail through a metal plate on one side of the truss. It’s okay to do this. Just make sure not to damage the plate when you do so.
As with rafter installation, use an 8d nail, making sure that about 2/3 of the nail length ends up in the wall plate. Make sure to toenail on both sides of the truss on each end. Use three nails for 2×4 chords, two on one side and one on the other, and four nails for 2×6 chords, two on each side.
2. Twist Strap
If you’re looking for an option that creates a more secure connection than your standard toenailing, consider these twist straps from Simpson Strong-tie. These straps wrap around the joint between the truss and the top plate. The strap attaches to the underside of the top plate, then twists over top of the truss top chord, holding both firmly together.
Simply bend the straps around the connection, then install with the specified fasteners. Although these might be trickier to install than toenails, they do offer more strength, resisting uplift better than nails. If you live in an area susceptible to damaging high winds, this is a great option for you.
TimberLOK’s alternative to nails and plates is also usable for trusses. Installation is similar to rafters; only you’re driving the 6” screw through the underside of the top plate into the top and bottom chords of the truss instead of into the rafter.
As with the rafter, make sure you drive the screw in at the point where the top plate and wall stud meet. To ensure a secure connection, make sure that the screw does penetrate all three pieces: top plate, bottom chord, and top chord.
4. Hurricane Tie
Hurricane ties are a great option for securing your truss to your top plate. Installation is the same for trusses as for rafters (see above). Instead of attaching the tie to the rafter, you will be attaching it to the bottom chord of the truss. Hurricane ties offer a strong connection that will provide you with the strongest resistance against uplift.
5. ML Angle Connector
Simple, strong and effective. These angle connectors from Simpson Strong-Tie create a solid connection between truss and top plate and are relatively easy to install. They work by creating a connection right at the 90 degrees joint of the truss and top plate.
Once your truss is in place, apply angle connectors to both sides of the bottom cord and install using Simpson’s 1/4” x1.5” strong-drive screws.
There are many good options to consider when determining how to attach your roof to the walls of the structure you’re building. Toenailing is one of the more straightforward methods of attaching rafters or trusses to the top plate, while hurricane ties offer superior strength to ensure your roof stays where it belongs.
When it comes time to attach your roof, be it trusses or rafters, be sure to consider what best suits the needs of the structure you’re building.