Tie In Unequal Roof Heights

Framing a roof of uneven pitch.

Tie in unequal roof heights.

To maintain a consistant ridge height in these situations the roof pitch must be adjusted. The 2015 international residential code does not require collar ties or collar beams. It is advisable to prepare a framing plan as shown in fig. Not infrequently a roof must be framed in which several pitches are involved.

After a taking some measurements and doing a bit of ciphering we established that the steepest pitch we could use on the porch roof was 4 in 12. Rafter tie a tension tie in the lower third of opposing gable rafters that is intended to resist the outward thrust of the rafter under load. Slide the right edge of the flashing under the highest roof pitch. 240 241 to calculate my front and back common lengths.

Position the flashing between the two roof pitches. A collar tie is a tension tie in the upper third of opposing gable rafters that is intended to resist rafter separation from the ridge beam during periods of unbalanced loads such as that caused by wind uplift or unbalanced roof loads from snow. The formulas below use the law of sines to calculate the unknown length or angle. Major pitch angle minor pitch angle span plate line difference calculate major minor runs theoretical plate line.

This first video shows how the finished roof planes in off angle roof construction will look when completed. Place the 2 by 4 inch piece of lumber along the center of the flashing. All of the principles necessary for framing such a roof have been developed. Collar tie is a colloquial term for collar beam.

We wanted to make the porch roof as steep as possible while keeping the peak of the roof below the wall to roof intersection at the top of the shed roof. I used will holladay s a roof cutter s secrets pp. I then did the calculations again using a different span same pitch and also came up with a difference of 23 3 4. I came up with 291 11 16 for the back and 267 15 16 for the front giving me a difference of 23 3 4.

Unequal pitch roof trigonometry calculating unequal pitched roofs is easy if you know what trigonometry functions to use. Cut two rafters with a circular saw to the pitch of the addition roof and nail them across the rafters on the old roof. A tension tie in the upper third of opposing gable rafters that is intended to resist rafter separation from the ridge because of wind or unbalanced roof loads. It remains for the student to make the applications to uneven pitches.

Where roofs of unequal pitch join it requires careful layout to create equalwidth soffits with equal height fascias.