Room-in-Attic Trusses: Turn Wasted Attic Space Into Living Space
When you look at the roof of a modern home, there can be a surprising amount of space hiding underneath it. In a conventional roof system, much of that attic may never become anything more than storage space, or it may not be usable at all.
But what if that space could become a bedroom, bonus room, office, bathroom, or even an entire apartment?
That's where room-in-attic trusses come in.
Room-in-attic trusses, sometimes called attic trusses or bonus room trusses, are engineered roof trusses designed with an open area through the center. Instead of separating the roof structure from the upper living area, these trusses allow the two to essentially be framed together.
For the right project, that can turn space that would otherwise be hidden inside the roof into valuable square footage.
What Is a Room-in-Attic Truss?
A room-in-attic truss is a roof truss specifically engineered to create usable space within the truss itself.
A typical roof truss uses a series of webs between its top and bottom chords to efficiently transfer loads through the structure. With a room-in-attic truss, the web configuration is designed differently to leave an open area in the center.
That opening becomes the future room.
The result is a structural system that can provide both the roof framing and the framework for an upper living area at the same time.
Create More Living Space Without Adding a Traditional Second Story
One of the biggest advantages of attic trusses is the ability to create additional usable space without framing a conventional second story.
With traditional construction, creating another level may require a separate floor system, walls, and then the roof structure above them.
A room-in-attic truss combines portions of those systems.
The bottom chord of the truss becomes part of the floor structure for the upper space, while the top chords form the roof above it.
This can reduce the amount of material and labor needed compared with conventionally framing a similarly sized two-story structure.
As Chad explains in the video, on some projects the cost per square foot of this space can be significantly lower than constructing a conventional second story.
Room-in-Attic Trusses Are Great for Space Above a Garage
One particularly popular application is creating a bonus room or living space above a garage.
Garages often benefit from having large, unobstructed areas without posts or bearing walls getting in the way. Properly designed attic trusses can span from one side of the structure to the other while creating usable space above.
That means the area upstairs could potentially become:
A bonus or entertainment room
An additional bedroom
A home office
Storage space
A bathroom
A guest suite
An apartment above the garage
Meanwhile, the garage below can remain open and flexible.
Of course, the exact configuration and required supports depend on the individual building and engineered truss design.
How Much Room Can You Get Inside an Attic Truss?
The amount of usable space available inside a room-in-attic truss depends heavily on the dimensions and design of the building.
Two particularly important factors are the building span and roof pitch.
As a general example from the video, a building approximately 36 feet wide may be able to accommodate a room around 18 feet wide. A 24-foot-wide building may result in a room closer to 12 feet wide.
Those aren't universal dimensions. Every project has different loads, geometry, bearing conditions, roof pitches, and design requirements.
However, they illustrate an important point: the larger the available roof structure, the more opportunity there may be to create useful space within it.
The roof pitch also affects the wall and ceiling heights available inside the finished room.
It Can Feel Like a Real Room, Not Just an Attic
When people hear "attic room," they may picture a cramped space where you have to duck underneath the roof.
That doesn't necessarily have to be the case.
The room-in-attic trusses shown in our video create a surprisingly large interior space. The example Chad walks through has usable areas extending toward the outside walls and a nine-foot ceiling, making the space feel much more like a conventional room.
Depending on the design, the sloped portions of the roof can also become an architectural feature.
Furniture can sit along the walls. Cabinets can be installed. Bathrooms can be incorporated into the layout. The space can be finished according to the intended use of the building.
In other words, you're not simply creating a bigger storage attic. You're designing the roof system around usable living space from the beginning.
Why Do Room-in-Attic Trusses Use Larger Lumber?
If you've seen some of our other Truss 101 videos, you've probably heard us talk about how engineered roof trusses can often use 2x4 lumber for their top and bottom chords.
Room-in-attic trusses are different.
In the example featured in our video, the trusses use 2x12 top and bottom chords.
There are several reasons for this.
The bottom chord is supporting a usable floor, so it needs to provide the stiffness necessary for a comfortable living space without excessive bounce or vibration.
The larger top chord can also provide additional depth for insulation within the roof assembly.
And when an attic room is located over an unconditioned space such as a garage, insulation requirements for the floor assembly also need to be considered.
Ultimately, the specific lumber sizes and configuration are determined through the engineering of the individual truss.
More Flexibility for the Space Below
The benefits aren't limited to the room upstairs.
Room-in-attic trusses can also provide more flexibility for the floor plan underneath them.
Because engineered trusses can be designed to span significant distances between bearing points, some designs can reduce the need for interior bearing walls or posts.
That can be especially valuable when the goal is an open garage, large living area, or flexible floor plan below the attic space.
Instead of designing the lower floor around numerous supports for the upper level and roof, the truss system can potentially transfer those loads to strategically designed bearing locations.
Planning for Room-in-Attic Trusses Early
If you're interested in creating usable attic space, it's worth having that conversation with your builder, designer, and truss manufacturer early in the process.
The size and shape of the room aren't arbitrary. Roof pitch, building width, loads, insulation requirements, bearing locations, ceiling height, and the desired finished space can all affect the final truss design.
Simply tell your truss supplier that you're interested in room-in-attic trusses and discuss what you're hoping to accomplish.
The earlier those goals are incorporated into the design, the more opportunity there is to develop a truss package around the space you actually want.
Make the Roof Part of Your Living Space
A large attic doesn't necessarily have to become wasted space.
With properly engineered room-in-attic roof trusses, the roof structure can create opportunities for additional bedrooms, bonus rooms, offices, storage, bathrooms, or even a living space above a garage while maintaining flexibility in the rooms below.
At Truss Components of Washington, we work with builders and designers to create engineered truss packages for the specific needs of each project.
If you're planning a new build and wondering whether the space inside your roof could be doing more, a room-in-attic truss system may be worth exploring.