How To Cut Rafter Birds Mouth?

If you are an active DIY-er or an experienced carpenter, you know the term birdsmouth. The birdsmouth is a joint quite popular in woodworking used to construct a roof or build a fence. Moreover, for a perfect fit for your roofing joists or rafters, you would need such joints. The birdsmouth cut or joint enables you to fit the roofing joist nicely. The birdsmouth joint is a traditional technique to secure the joists on a wall plate. So how to cut rafter birds mouth?

Contents

How To Cut Rafter Birds Mouth – Step By Step Guideline

Step 1

First, the processes align the stair gauges (clamp) along the frame square at the rafter top edge. The gauge must be aligned in such a way moving up and down the rafter is easy. Start marking; locate the ridge to cut at every 1 feet gap. Continue throughout the length of the rafter.

Step 2

The notch that rightly fits the top of a wall is called birdsmouth. You are advised to measure the plumb cut. The thickness of the wall assembly must match the level seat.

Step 3

Many users prefer the long tails to remain and then snap a line to suit the place. But the process is done in advance for plumb cut rafters. You can achieve a proper birdsmouth with actual measurement.

Step 4

A cutline should be marked on the rafter to secure its alignment to the ridge board. The rafter must be cut half the ridge board’s thickness from the top of the rafter. You are required to measure the difference created on the rafter body.

Step 5

Use a circular saw to make the cutting. Remember, the other entire rafter would be duplicated. Hence the cut should be accurate and precise. You should ensure having sharp blades, and asset square must be there along with the circular saw.

Step 6

You need a handsaw to finish creating the birdsmouth. Use this handsaw to cut into the corner from both sides.

Step 7

It is a fact; framing of lumber won’t be straight. However, it would be better to replicate. It would be wise to put the pattern one above other. A quick-grip clamp can keep the rafters together.

What Do You Need?

1. The Stair Gauge

These are a pair of clamp-like accessories that make the laying of rafters useful. It is a quite handy device of hexagonal shape with a hollow in between. Thumbscrews are there, which tightly hold the framing square. This accessory helps the square to glide consistently along the rafter.

2. The Rafter

The essential component of roof framing is the rafter. If you are building a simple or gobble, shed a single rafter is sufficient. It would help if you lay out a common rafter. You need to know the pitch of the roof and run per foot. The length covered by a rafter is known as the run. The run is usually measured as per the length between centers of the ridge up to the top wall edge. Once you know the details about the roof, i.e., pitch and run, you would set the layouts of cuts. What is “Step-off”? It is using Framing Square at 1-ft increment as the most straightforward method.

3. The Framing Square

To lay off the rafter, the Framing Square is most vital. For the proper dimension, this device is beneficial. Along with the stair gauge, they can produce a layout for cutoffs. They can be used for successful “step-off” activity.

4. A Circular Saw

The cut produced on one rafter will be used as a pattern for other rafters. So the cuts must be precise and accurate. So, you should ensure the blade of the saw must be sharp. Again, the saw must be having a set square. A circular saw can also be used to cut ties, micas, corks etc.

5. A Hand Saw

This tool will be required for finishing the process of cutting the birdsmouth. Also, cutting corners on both sides of the cut can be done with a hand saw.

6. A Marker Pen

It is required while the “step-off” marking is done using a framing square. It is an essential accessory to correctly depict the scoring positions, i.e., one foot apart.

7. Clamp

It won’t be possible to make equal cuts every time. So we need a pattern to make cuts unique. If you have a helper to hold the rafter pieces together, or else clamps can help.

FAQs

1. What is the requirement to cut birdsmouth?

The rafters generate a lot of load onto the side walls. Cutting the seat like birdsmouth reduces the overall weight transfer.

2. How much can be cut from birdsmouth?

In general, one-third of portions can be cut from timber but not more than half. It is as per the thumb rule.

3. Which among rafter and trusses are used today?

The use of rafters is less nowadays. The rafters are quite advantageous, and it is much simpler to use rafters for home building. Trusses are less time consuming to install, and price-wise is less, so trusses are used more.

4. What is the spacing requirement between rafters?

In general, the spacing between rafters is 12, 14, or 16 inches. The measurement is done center to center of rafters in a flat position.

5. What is straight cut meant for?

Vertical and straight cuts of rafter are represented by plumb cut. This method of cutting is used to top or tail cutting of birdsmouth.

Final Thoughts

The woodworkers use birdsmouth for rooftop farming. It’s a scientific method to handle gravitational pull and distribution of load. This joint looks like the mouth of a bird from side hence named so. And our guide on how to cut a birds mouth will help you with that. The cost for birdsmouth and the time needed for installation are more. Equipment like framing square, and stair gauge, circular saw, etc. are used.

Comments

Vincent W Herlihy says

April 18, 2021 at 7:22 am

These directions don’t make any sense, in particular because they gloss over details and as they’re filled with spelling, grammar, and syntax errors. Stating the obvious, for example, that you must measure, without clearly defining the objective, or clarifying the text with a diagram, makes these instructions worthless. I read them three times and still don’t have a clue what the author was trying to impart. Additionally the FAQ’s are of no value; basically having little to nothing to do with cutting a birds mouth. I realize the author was trying to be helpful, but this posting should either be edited to make it concise and intelligible, or it should be taken down.

- D Moppin says
  
  November 5, 2021 at 4:19 pm
  
  Mr. Herlihy is not entirely incorrect. But, let’s not murder the writer. I find there are some gems in his writing. (that is for me anyway) I suggest you attempt to find a perfect all encompassing source of information on the subject that is easily understood by all. I haven’t found one.
  I suggest we applaud and thank the author for sharing his effort.
  If we discourage all imperfect efforts we will never get to perfect.
  Maybe you should offer suggestions, corrections and constructive advice. end of message

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