Types of Roof Trusses - Costs and Common Uses
Selecting the best type of roof truss for a house is quite challenging. Functionality and aesthetic conditions will lead the considerations of the type of roof truss that you will be selecting in the construction of houses and buildings. Costs can vary considerably, but there are ways to keep expenditures low.
The typical truss is recognizable by its triangular shape and is most often used in roof construction. Each roof truss has pros and cons, and it must be designed to suit specific conditions and purposes. It is important to have in mind what type of look you want to have in your finish building when selecting the type of roof truss, as they often dictate the final shape and slope of the roof.
When Does A Roof Truss Make Sense?
Sometimes a roof truss can makes sense, as it will be able to meet certain design weather considerations that often trigger expensive, special building code requirements. These are the following advantages that can be obtained when using a truss:
- Workers with less experience can install roof trusses reducing labor costs and facilitating the installation process vs. other roof suspension systems.
- Some designs can require having fewer load bearing walls as these trusses can be used for achieving longer spans, creating open living spaces.
- There can be savings in building materials. Often, lighter and less expensive materials can be used throughout, when combined with a truss.
- Installation of trusses can be achieved in 1 day, as they can be prefabricated near the site and erected using a lightweight crane or construction equipment.
Common Types of Roof Trusses
There are many types of roof trusses, but the four variants below comprise the lions share of constructed ceilings.
The Parallel Chord Roof Truss
Commonly used in cathedral ceilings, its cost is higher because it requires the use of steel members to serve as bracing. The complexity and numerous wood members used is another disadvantage. Thermal bridging caused by the steel braces can decrease energy efficiency, but many consider the simple lines of the parallel chord roof truss both functional and appealing to the eye.
The Raised Heel Roof Truss
This method allows for greater energy efficiency. This roof truss reduces the condensation problems since they create a vapor barrier, and is commonly seen it humid climates where mold is a common issue. It requires a soffit siding and additional insulation work from the onset, which adds up to elevated construction costs. It can be designed to span an area and provide full-depth attic space.
The Scissor Roof Truss
Also commonly used in cathedral ceiling for its construction convenience, this type of roof truss reduces the need for a bearing beam. It uses lower chords that slope inward, instead of being horizontal. One of the disadvantages of using this type of truss is the problem in completing insulation which, while already hampering aesthetic appeal, also elevate construction costs.
The Dropped Chord Roof Truss
The dropped chord variant is composed of a convention truss, with a secondary chord truss suspended below to help reduce uplift. Similar to the Raised Heel Truss, this type also creates a vapor barrier creating great insulation characteristics. Vapor barrier needs additional blocking and siding in the intersection of walls and ceilings, adding to the construction cost.
How Much Will It Cost?
There are certain factors that will have an important impact on how much the truss will cost. Studies from the mid-2010's have shown that for an average American house, the roof truss can cost anywhere between $12,000 to $15,200. A breakdown of the cost often leans heavily on materials, so there isn't much room to save money.
The roof truss labor costs often exceed $2,500. A crane rental will be more than $700. Decent quality lumber is essential, and will almost always exceed $10,000, and the scrap disposal cost between $200-500. Conventional framing is typically more than 60 percent more expensive than a prefabricated truss, and will cost more in materials. This is an important consideration if customization is a priority to the project.
Is It Possible to Save Money?
In general terms, and if you want to save money while being practical, a 4/12 pitch roof is the most economical. It is strong but shallow, maximizing the use of lumber using available and ordinary lumber sizes. A 4/12 pitch means that the roof rises 4 inches for every 12 inches of run. There's already been mention of using a prefab set-up when appropriate, and you can always attempt to negotiate a lower labor fee for larger projects. Generally though, since most of the cost of a truss lies in the raw materials, it is difficult to save a significant percentage on the finished project.