When you bring outdoor items to your garage, your garage space becomes cluttered. The best way to free your garage is by storing the items in your roof truss. But the question comes – how much weight can you hang from a roof truss?
As roof trusses are made to support the roof of the structure, it can’t bear heavy loads. If you cross its load capacity limit, your building’s safety and stability will be compromised.
How much weight can a roof truss bear?
Before jumping into the main topic, you need to know about the design, load types, etc., of roof trusses.
What is a Roof Truss?
Roof trusses are made to support the structure of a roof. As a roof truss uses very little material, it requires minimum labor and costs. Again, roof trusses can carry a specific amount of load. If this load is exceeded, the structure will be in danger. That’s why before putting any load on the roof truss, garage owners must know how much load they can put on their roof truss.
Design of the Roof Truss
Roof trusses are built to spread the load of the item downwards and outward sides of the building. This becomes possible with the help of top chords.
These top chords are entangled with the bottom chords horizontally. Again, these horizontal bottom chords play a crucial role in carrying the loads.
2 Types of Loads – Truss Bottom Chord Dead Load & Live Load
It’s a temporary load that puts pressure on the structure. Some of these live loads are- precipitations, foot traffic, winds, and so on.
While designing the roof truss, engineers will have to follow the local building guidelines for live loads and build the roof truss accordingly. Usually, if the bottom chords work as a floor joist for residential space, the load capacity will be around 40 pounds per square foot.
Unlike live loads, this type of load is permanent. The load of the structure, materials, furniture, drywall insulation, a load of the stored items, etc., are some of the examples of live roads.
Roof trusses are made in a way that can handle both live and dead loads. If the overall load exceeds the cumulative limit, the structure of the building will be in danger.
The dead load capacity of a roof truss depends on its materials, such as the drywall insulation. Usually, the dead load capacity of a roof truss is about 7 to 10 pounds per sq. foot. However, you’ll have to include the hanging weights as well to calculate the exact dead load of the roof truss.
Factors to Consider – Roof Truss Weight Calculator
Local Building Code
Before you build your roof truss for your garage space, you need to understand your local building code. Usually, these local building codes follow the IRC or International Residential Code.
According to the IRC, the minimum live load capacity of a roof truss for non-sleeping areas should be around 40 pounds per square foot. Again, if it’s built for sleeping areas, it should be around 30 pounds per square foot.
Apart from this, you’ll have to know about the deflection of the floors as well. According to the IRC, floor deflection cannot exceed 1/360 of the total floor.
This table is used to determine whether a roof truss design will meet the local building guides or not. In this table, strength is measured by the Fb value, and the stiffness is by the E value.
Generally, these values are used by engineers while building roof trusses for buildings.
Apart from local building code and span tables, you’ll have to consider the dead loads and live loads of the roof truss. As I mentioned above, the live load of a roof truss should be around 40 pounds per square foot, and the dead loads should be 8 to 10 pounds/sq. foot.
Determine How Much Weight Can You Hang from a Floor Truss
To determine the load limits, you’ll have to first consider the lumber grade, size, span, and spacing of your floor. You’ll find this information on a stamp of the floor joist.
After that, use the value table to find the Fb values or strength values. If your floor area is ten feet by eleven feet and built with number one grade two by six Douglas joists, according to the design table, your Fb value will be 1495, and the E value or the stiffness will be 1,900,000.
Then use the span table to cross-check the values you got from the design table. After determining all the load limits, you can find out the maximum load capacity of a room as well.
FAQs about Attic Truss Weight Capacity
1. How heavy Can I Hang on a Drywall?
2. What is the Maximum Load Capacity of a 2×8 Ceiling Joist?
3. How Much Can I Hang from a Stud?
4. What is the Weight Capacity of a 2×4 Stud?
The general rule of thumb is you can hang around 5 to 10 pounds of weight from a roof truss. Remember, if you’re planning to build a roof truss for your garage, it’s recommended to hire a structural engineer. Because if all the building codes and procedures aren’t followed correctly, your building’s stability can be in danger.
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