Rafter Layouts (Birdsmouth, Fascia, Soffit)

3:05

12:04

1.6K views

At 3:05 in

Speed Square Mastery: Stop Using It Wrong

Watch on YouTube

What happens here

Speed squares are invaluable for roof rafter layouts, including birdsmouths, fascia, and soffits. To find the pitch of a roof, place the speed square on the rafter with the pivot point at the top and pivot it until it's level. The 'common' scale will indicate the roof's pitch (e.g., a '4' on the common scale corresponds to a 4/12 pitch). Once the pitch is known, use the speed square's 'common' and 'hip-val' scales to mark the exact cut lines for the birdsmouth (the notch that sits on the wall plate), fascia (the board covering the rafter ends), and soffit (the underside of the eaves). Some speed squares, like the Empire model, may also feature a conversion table that directly correlates common pitches to degrees, simplifying the process.

Goal: Layout roof framing cuts for rafters, fascia, and soffit

Tools and materials

Small Level — Ensuring the speed square is level when determining roof pitch
Swanson Speed Square Swanson — Measuring roof pitch and marking complex rafter cuts
Yellow Carpenter's Pencil — Marking the cut lines on the rafter
Wood Board — Demonstrating rafter cuts and pitch measurement
Wood Post — Supporting the rafter for demonstration

What they say

(1,209 characters)

Hide

Now speed squares can do rafter layouts and finding the pitch of your roof all by using our hip and valley and common. You can cut bird's mouths, soffit and fascia all using a speed square. So one trick to find the pitch of your roof is to go ahead and put your speed square on there like that and put your pivot at the top and pivot up to where your speed square is level. So if we grab a level here and we bring it all the way up to where it's level. Like that. We know that this roof pitch is a 4 12 pitch, right? And now we're with that information, we're going to cut out our bird's mouth and I'll show you how to do that. All right, so say we want to cut a rafter for the other side of our mock up here. Right here on this scale you have your hip and your valley. And then you have your common. So your hip and your valley is when you have like two peaks that come like this and then you got a two peak over there. You would have a valley and a hip, right? Your common is for your rafters. So go ahead and put your square on the edge of your rafter and rotate your common until you find what pitch you want. In our case, like this, it's 4 12. So take your 4 12 just like that. Bring it a little bit more

Auto-generated from the video audio.