Roof trusses make up the structure that supports shingles or other roofing materials. You can use timber to build this structure yourself. Sturdy roof trusses will improve the structural integrity of your roof, support heavy roofing materials, and prevent damage in areas with heavy precipitation. Here is what you need to know about how to build roof trusses if you want to create this framework yourself.
Make Sure Roof Trusses Are Your Best Option
Rafters and trusses are the two most popular roofing options. It's essential to consider your budget and the roofing material you will use for your project.
Trusses tend to be more affordable and support slate and other heavy materials. However, rafters make more sense if you want to have some open space in your attic. There are roof truss designs that leave room for storage, but rafters are the most convenient option if you want to use your attic as a living space.
Installing insulation is easier if you use rafters to support your roof. The open space gives you easy access to the rafters, and you can fill in spots as needed. Installing insulation inside of the truss structure is more complicated.
However, roof trusses tend to be easier to install. You can build a truss framework with several small elements that you can assemble and get on top of the house yourself. Depending on the scope of your project, you might be able to lift each component of the framework without renting special equipment.
Regardless of the option you choose, check your building code. Find out about the framework designs and materials you can use for your project. Pay attention to size requirements for your roof structure.
Explore Different Truss Configurations
There are different ways to assemble trusses. The best framework design depends on the size and weight of your roof. Some plans will support more weight, while others will leave more open space for storage.
The truss configuration you choose will impact the cost and complexity of your project since some designs require more elements and result in heavier trusses.
The different types of truss frameworks share a common triangular structure. Each truss includes two triangular shapes facing each other. You will notice differences in the truss web that connects the top and bottom chords of the trusses.
If you are wondering about how to build roof trusses with a simple structure, think about using a classic M-shape. This design uses three vertical posts to support the top chords and two diagonal pieces to distribute weight evenly.
Scissor trusses are another design option to consider. The bottom chord isn’t a flat piece. Instead, scissor trusses use slanted bottom chords to create a cathedral ceiling in your attic. You can combine the classic M-shape with the scissor design to have a cathedral design on one side of your attic.
There are other configurations to consider, including a mono-pitch design if you want to build a slanted roof, a simple king post design if you are using lightweight roofing material, or an open plan design if you're going to turn your attic into a livable space.
You can also find templates for flat truss designs, fan frameworks, fink shapes, and dual-pitch roofs. These designs spread weight slightly differently by using a variety of truss web configurations.
If you are using heavy roofing materials, look into using a double-fink or double-home framework. These designs include more elements that help distribute weight.
Regardless of the type of truss configuration you choose, you will also need to build gable trusses to frame your roof. You can typically use vertical pieces to create a gable truss but might need to use a scaffolding design that combines horizontal and vertical pieces to build higher gable trusses.
How To Build A Roof Truss
It’s easier to build roof trusses if you understand the purpose of the different elements:
Design elements will vary from one type of truss framework to another. Some designs use a central king post while others use two or three vertical posts to distribute weight more evenly. A fink or double-fink framework doesn’t use vertical pieces and relies on a crisscross design with diagonal pieces instead.
Some truss designs use additional elements. You can improve the structural integrity of a roof truss by connecting the top chords to the bottom chord with a rectangular piece of plywood or gusset. It’s best to use this technique if you need trusses that can support heavy materials.
Braces are another option to explore if you want to improve the strength of the roof trusses.
You can build trusses with square or pointed extremities depending on the type of overhang you need. You can create a pointed overhang by connected the extremities of the top and bottom chords with a soffit block and heel wedge.
You will need to add a heel spacer between the extremities of the top and bottom chords if you want to create a square overhang.
Materials And Sizes
Timber is the most common choice for roof trusses. You can use 2x6 or 2x8 timber depending on how much weight the trusses will support. It’s usually best to use a 2x8 piece for the bottom chord.
You can also work with steel or aluminum. These materials are more durable, but timber is more affordable. Steel and aluminum trusses typically don’t do well in hot climates. However, these materials are worth considering if you live in a cold and humid environment.
You need to carefully measure the different elements of the trusses so you can build identical pieces for your framework. Don’t forget to add a few additional inches to create an overhang.
Look for roof truss templates to find the right angles and proportions for the truss design you want to use. Figure out the length of the bottom chord and calculate the length of each element to create a structure that is proportional to the length of the bottom chord.
Connector plates are crucial elements that you need to use to assemble your roof trusses. You need to secure the different pieces with connector plates to create a sturdy structure that can support the weight of your roof.
You need to use a connector plate at each intersection of the truss design. Use galvanized steel connector plates since other materials won’t be sturdy enough.
You should use galvanized steel screws to secure the plates to the timber. Ideally, you should use screws that are at least 2” long. The thickness of the screws depends on how thick the pieces of timber are.
You can use simple nails to attach the pieces of timber and form the triangular shape of the truss. Your next step should be to secure connector plates to each intersection with a hammer. Connector plates have a face with multiple spikes that will get into the timber and secure the intersection. The best way to create a sturdy wood-to-wood connection with those plates is to attach them with a roller.
You can then secure the connector plates to the timber by adding screws. Aim to use four or six screws per connector plate.
Figure Out Truss Spacing
Spacing is an important design element to figure out since it determines how many roof trusses you will need to build. You would typically place trusses 18 to 26” apart when building a framework for your roof.
Placing the trusses closer together will increase the weight of the framework, but it means you can use heavier roofing materials. You need to find the right balance between spacing and increasing the weight of the frame.
We recommend purchasing roofing templates or having an architect design a template for you. A professional will be able to figure out the ideal spacing depending on the size of your home, roofing material, and truss configuration you want to use.
Getting The Trusses On The Roof
You will need three or four people to get trusses on a roof safely. Remember to always lift the trusses upside down so you can easily maneuver them. It’s also best to always use two points of contact to lift trusses. Using a single point of contact might cause a truss to spin due to its triangular shape.
Start by figuring out spacing. You can then place trusses on the ground to roughly reproduce the spacing pattern. It will be easier to assemble the framework if you can get trusses up on the roof as close as possible to the spot where you need to attach them to the bearing walls.
Renting a crane is the easiest way to lift trusses on your roof. However, equipment rental can be expensive, and you might not know how to operate a crane.
Using scaffolding is a more affordable alternative to explore. You can use ropes or chains to lift trusses along the scaffolding. If the roof of the house is low, you might be able to have two or three people on the ground lifting the trusses and handing them to the roofers.
Take safety into consideration when figuring out the best way to get trusses on the roof. Don’t hesitate to spend a little more on your project to rent equipment or build sturdy scaffolding.
How To Secure Gables And Trusses
It’s best to begin your project by securing the two gables. Gables are larger than trusses, and getting the last gable on the roof can be difficult once you have installed all the trusses.
Make some marks in advance to keep track of where you should secure the trusses. You should also make marks on the trusses to indicate how much overhang you will leave. Use as many points of connection to bearing walls as possible since these walls can support more weight.
You will need to attach the trusses to double top plates installed on the bearing walls. If the bearing walls don’t already have plates, install them before getting the trusses on the roof.
Use top plate anchors to create a sturdy connection between the bottom chords and the top plates on the bearing walls. Check the angle of the trusses to make sure they are perpendicular to the ground before securing them.
If you need to attach a truss to a non-bearing wall, it’s best to use slotted anchors. Make sure you use plates or slotted anchors that are large enough for the weight and thickness of the timber.
Common Mistakes To Avoid
Here are a few mistakes to watch out for when building and installing roof trusses:
You should have a better idea of where to get started with your roofing project now that you know more about how to build roof trusses. If you aren’t confident about your ability to build roof trusses, think about ordering those pieces from a manufacturer. You can easily find pre-assembled trusses to create a wide range of framework designs.