When it comes to roof installation, the choice of the rafter cut is one of the biggest decisions you’ll have to make.
We know just how challenging it can get to make this type of decision on your own, especially if you’re not equipped with the right information.
Birdsmouth cut is certainly one of the most popular and common choices when it comes to roof rafter or joist positioning, but are there any alternatives that should be considered?
In this detailed guide, we will help you find the best alternative to birdsmouth cut by introducing the most efficient, durable options.
The best alternatives to birdsmouth cut
Is the birdsmouth cut structure the best choice for your roof, and what techniques could replace it? Keep on reading to find out more about the best alternative to birdsmouth cut.
1. Hurricane ties
One of the primary choices when it comes to replacing birdsmouth cut structures in your roofing are hurricane ties.
As the name itself implies, the structure should be so strong that not even a hurricane should disrupt it, let alone compromise your roofing.
That being said, hurricane ties, also known as hurricane straps or strips, represent an excellent choice for areas with extreme weather conditions and strong wind when you want to ensure that you’re providing the highest level of security for your roof.
Just like a birdsmouth structure, hurricane ties ensure that the force on the roof, as well as the roof weight, are evenly distributed all around, securing the roof in place.
Hurricane ties are secured into the roof structure with bolts, screws, or nails, which contributes to the overall structural integrity of your roof.
These ties are wisely distributed throughout the roof structure, especially in roof purlin plates, wall plates, rafters, as well as floor plates to ensure that the joints are fortified.
What’s more, hurricane ties have been found to protect timber and improve its longevity in wooden roofs prone to decay and overall structural failure.
2. Rafter ties
The sole purpose of rafter ties is to connect the opposing rafters and strengthen the roof or attic trusses.
Rafter ties can be wooden or metal, and both are equally as popular in residential roofing. Wooden rafter ties mechanically tie the opposing rafters together, adding more stability to the attic trusses.
Metal rafter ties, on the other hand, represent a connection between the supporting wall and the bottom part of a rafter. The choice of the rafter tie depends upon the ceiling joist, as well as the overall ceiling design and height.
Wooden rafter ties represent a better solution for shallow tray or flat ceilings since they limit the interior ceiling height due to their full-spanning structure.
Metal rafter ties create a connection between the supporting wall and a single rafter, so the ceiling height doesn’t make too much of a difference.
In case you choose metal rafter ties, it is recommended to add a protective galvanized coating, which will basically protect the base metal from corrosion. Corrosion is a very serious issue when it comes to metal rafter ties, as it compromises the structural integrity of the roof by creating weak spots.
3. Stud cutting
In case you don’t want to go through with the birdsmouth cut method, or you simply don’t think it is the right solution for your roofing after consulting with a professional, it is possible to get the desired outcome by cutting the studs.
When it comes to “tailoring” the studs, it is necessary to determine the pitch of your roof accurately, which is why many people leave this process to roofing professionals.
Also, it is necessary to measure the ridge beam, as well as the roof span, before you begin cutting. In case these measurements aren’t correct, the roof joists or beams won’t sit properly, creating weak spots in your roof.
What’s more, using studs with variable pitch connectors is the best way to increase the support the studs offer for your roofing structure. You can also add HCPs to each corner of the roof to make sure that the load is evenly distributed between the beams.
4. VPAs
VPAs (variable pitch connectors) represent probably the most durable, high-quality replacement for birdsmouth cut.
Since they’re made of galvanized steel (and are protected against damaging corrosion), variable pitch connectors are a great way to create a sturdy, reliable connection between the top wall plate and joists.
Once the roof rafter has been installed, you can simply attach a VPA to it, connecting the rafter to the outside corner of the wall, which further increases the overall stability of your roof.
One of the best combinations for top-notch roof security is the combination of VPAs and HPCs (hip corner plates).
While this combination will ensure that the weight of the roof is evenly distributed and there are no weak spots, installing VPAs in combination with HPCs is quite easy compared to other methods, and it doesn’t require too much time.
However, keep in mind that VPAs are only suitable for slopes in the range of 3:12-12:2.
Pros and cons of birdsmouth cut
Birdsmouth cut, also known as birdsmouth joint, or birds beak cut, is a cut that literally resembles a bird’s mouth, hence the name.
The main role of this cut is to keep the rafter in place and connect the supporting walls and the roof.
Thanks to this design, the rafter is secured on the top of the plate horizontally, which allows for the vertical front part of the plate to butt up to the other end of the plate.
Long story short, the birdsmouth cut secures the roofing, strengthens the supporting walls, and transfers any force from the roof to the foundation through the supporting walls.
But, how is the rafter secured to the wall plate, and what is it that ensures that they remain connected?
The process of toenailing (side-nailing or skew) entails securing each side of the rafter with nails at an angle, directly into the timber at the top of the wall plate.
Once the rafter is secured to the timber, you can rest assured that you now have a sturdy roof joint.
The birdsmouth cut actually consists of two cuts: the seat cut (the horizontal cut) and the heel cut (the vertical cut).
Keep in mind that the birdsmouth cut is only a good choice for a traditional cut roof and not for roof truss since any additional cuts could seriously jeopardize their structure.
Another important factor if you choose a birdsmouth cut for your roof is that both of its cuts need to be extremely precise, making sure that the seat cut aligns and sits at the very top of the wall plate timber.
In case the cut is overhanging the wall plate timber, this means that the cut hasn’t been properly executed, and this represents a major liability for your roof.
Basically, the overhang would be the weak spot of the entire structure. As long as the cut and the timber are aligned, the roof load will spread evenly, and there won’t be any crush points.
Would the rafters still be secured if the birdsmouth joint technique wasn’t used?
While you could secure them to the wall plate, this wouldn’t necessarily mean that the roof would be able to evenly spread the load, which is where the birdsmouth joint comes into play.
Without a properly executed birdsmouth cut, there would be crush points that could cause the rafter to crush the timber under the load, as the crush point would not be able to handle the weight.
The load is not the only enemy here, as gravity would impose a problem, as well. As the gravitational force is pushing down on the roof, the roof construction needs to allow it to travel through the supporting walls down to the foundation.
The birdsmouth joint method allows for the gravitational force to be transferred at a diagonal angle, ensuring that the force is applied downwards.
How to choose the best alternative to birdsmouth cut
When it comes to choosing the best framing method for your roof, there are a couple of factors to take into consideration, especially if you’re living in an area prone to harsh weather conditions.
Birdsmouth cut is one of the most durable, reliable methods when it comes to securing your roof, even in problematic areas. However, it does usually require a professional to help with installation, as it must be executed perfectly in order to provide the security it promises.
If you’re not too fond of the birdsmouth method, or you’d simply like to try something different, hurricane ties are definitely among the most popular options for windy areas prone to natural disasters.
Rafter ties are quite easy to install, and they also come in two different variations, depending on the preferred method, as well as the design of your ceiling.
Stud cutting is the most affordable option out of all the methods we’ve discussed in this guide, as all you need to do is cut the studs accordingly. However, it is necessary to determine precise roof measurements in order for this method to work.
Finally, many people gravitate towards VPAs, especially in combination with HPCs, as this option has proven to be quite durable and long-lasting, but it doesn’t require too much effort or time to be properly executed.
David Kessler is a CSLB licensed contractor with over 25 years of experience. He is specialized in home building, construction, and electrical works; he also has a keen eye for interior design and, over the years, has collaborated with various architects.
