Evolution in roof framing has been visible over the years. Gone are the days when rafters dominate the construction industry when it comes to roof framing.
At present, 90% of home and building construction now use trusses as their roof frames. With this dramatic shift, one could ask, what happened to rafters? What are its pros and cons? Which one is really better?
To settle these questions once and for all, let’s plot these two roof frame types objectively against each other in this post.
Related: Parts of a roof
What is a rafter?
Rafters are conventional roof support or frame and are also called as stick frames which basically support the roof and roof sheathing. Rafters are usually assembled by attaching sloping wood boards to the roof’s peak (commonly known as the ridge board) up to the exterior walls. Rafters are usually made out of 2×8 or 2×10 lumber.
Rafters are secured at the bottom through ceiling joints while collar ties are installed horizontally at the mid-part of the rafters to ensure that the rafters and the roof planes are held together in place.
What is a truss?
A truss is a pre-made and pre-assembled triangular frame for roofs. The structure is made of triangular webs that hold and support the roof with the external walls of the home. Like rafters, trusses are also made out of sloping planks called beams.
Running horizontally through the length of the beam would be chords. The webbed, triangular structures that make up the truss are specifically designed to give support to a wider roof area. Multiple trusses are actually installed in homes spanning from end to end.
What’s the difference?
The main difference between trusses and rafters is how they are built. Conventionally, rafters are built on-site after measuring the dimensions of the roof. Trussers, on the other hand, are mostly pre-made in factories to be delivered on-site, ready for installation.
You would find rafters in older model homes and trusses in newer models. Although this is not always the case and some new model homes still install rafters instead of trusses, a significant percentage of home construction nowadays makes use of trusses over rafters because it saves time.
Rafter pros and cons
Since there are still homeowners that would prefer the use of rafters for their roof frame, we have to flesh out the pros and cons of rafters. This would give you a comparative understanding too of what to consider before you decide on what roof frame to install.
1. Generates more attic space
We can all concede that the attic will always be a promising space. At some point, it might be converted into an additional room and most times, it works as a storage area.
Using rafters ensures that there will always be enough space in the attic. Aside from this, it also offers greater ceiling options if you want to renovate in the coming years.
2. Provides insulation for the attic
Without the thick, webbed structures of trusses, rafters accommodate the faster installation of devices and measures to insulate the attic. Having more space in the attic makes insulating methods easier to employ.
3. Does not require lead time
Since rafters are built on-site, you will not need to measure the roof dimensions ahead of time and send it to the contractor that will install it. Getting accurate measurements and having it assembled with precision takes time.
Paradoxically, rafters can also be time-consuming. Since it is built on-site, it will need many people to put it up (from measurement to actual installation).
As per the usual estimate, rafters for a large house may take more than a week to build. Hence, rafters are not only time-consuming but are more expensive to make too.
2. Skilled work
Since home construction has shifted to trusses in the last few years, the availability of skilled workers to build rafters has dwindled in number.
If you consult with contractors, chances are they will convince you to just shift on trusses. This will leave you with the additional job of finding skilled workers that will build the rafters for you.
Truss pros and cons
In the same way, trusses are not perfect and it has to be objectively evaluated too through its share of pros and cons.
1. Has gone through quality control
Because they are factory-made, you can be assured that trusses have gone through rigid quality control. Note that trusses are measured digitally and are constructed with precision.
Sometimes, third-party quality control inspections also take place just to make sure that sold trusses are sturdy and reliable.
It is also an upside to know that truss delivery is always on-time and that building the entire frame is just three days max.
And since they are not built on-site, you are more assured that trusses and the lumber used in making them were not heavily exposed to elements that could easily wear them down.
3. Durability and sturdiness
Trusses are specifically designed to be able to withstand the varying weights and cover of roofs so you can count on it for its durability and sturdiness.
The webbed, triangular design makes use of cheaper and shorter wood planks. In a comparative report done by the home builders’ association, labor costs and material costs for trusses are 16% cheaper than rafters.
1. Lessened attic space
With the inclusion of webbed, triangle structures in the frame, the attic space is lessened. Hence, you can no longer convert it into a room in the future and your storage space will be lessened too.
2. Delivery expenses
Since the final product is the roof frame in itself, it will be bulky and will be in need of at least a 16-wheeler truck to be delivered. Of course, you will shoulder this added expense as well as the installation expenses that will happen after delivery.
3. Less room for future changes
Future alterations in the roof frame is strongly encouraged once you have installed trusses. It is considered as an independent structure and modifying it will greatly diminish its structural integrity.
Which one is better?
The answer to this really depends on you. If you feel like your home will undergo modifications in the future, you should go with rafters. But if you think that there is no need for greater attic space and that there will be no roofing modifications in the future, trusses would be an economical choice.
Can you replace trusses with rafters?
Yes, it is possible but it is labor-intensive, needs professional work, and will charge you a lot. The reason is that you will have to check the load-bearing capacity of your roof. Before taking out the trusses, you will have to add more support rafters one by one until you can cut all the trusses off.
Honestly, there is no great difference between rafters and trusses. As a matter of fact, even their appearance would be identical.
The separation, however, comes in the webbed triangular structures in the trusses which elevates the load-bearing capacity of the roof and the time-saving feature of trusses. Basically, it is still up to you to decide if you will choose trusses or rafters as your roof frame.