Roof Guidance

When it comes to residential design, some things have come very naturally to me.  Modeling, layout, colors, textures, and balance, for example.  I love envisioning future spaces, and adjusting current layouts to achieve better flow and support the lives of the inhabitants.  Give me a color — say, orange!  Gray!  And my mind starts filling instinctively with neutrals, patterns, textures, furniture pieces, decor, contrasting pops, to fill a room or home with life.

Not so with roofs.  I enjoy imagining ceiling planes, and the interior experience, but sketching exteriors and roof planes is my least favorite part of residential design.  For now.  I hope someday this will excite and engage me, but I find the mapping of hips into hips, modeling eaves, fascias, and exterior trim, just not fun.  Especially when I have to get the exact roof measurements and angles of an existing structure.  Handiness is not my middle name.  Clumsy is more like it.

Enter my mentor, Uncle Lance, who is a wizard at design and construction, having mastered that impossible point between artistry and pragmatic building.  He has also succeeded in the field for many years.  Here I share his exact guidance.  I hope it helps someone as it has helped me:

  • I always start, when possible, with existing house plans and treat whatever pitch is noted with reserved enthusiasm.  So often, the framers make in-process adjustments that detour from the architect’s specs causing a “5/12” pitch to morph into a 4/12-6/12. ( I’m assuming you’re familiar with the common roof spec that uses 12 as the right triangle base and some value as the triangle’s height….together, setting the pitch of the hypotenuse(the roof).)
  • next, I use gable ends where I can measure the run and rise on a side wall….either using a level to get the triangle’s base and height……….or easier………..using horizontal siding to get a fix on the drop in the roof over some measured distance(horizontal)
  • then, if there are cathedral ceilings on the interior, I would use those.
  • then, I’d crawl into the attic and take rise and run measurements there(that framing is actually a more reliable base for pitch calculations since the finish roof is often subject to multiple re-roofs which can make for somewhat fuzzy pitch measurements.
  • and, yes, I do get up on the roofs when necessary but only for a couple of spot checks using a level and a protractor(the level sets perpendicular and the protractor shows the roof’s angle off perpendicular.

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  • finally, I take a lot of photos………many used for SketchUp photo matching.  With several external photos and the SU matching processes, I can get a fairly accurate model of the structure with only a few known measurements.  And even though the photos are perspectives and subject to the vagaries of vanishing points, the modeling process produces a shape that can be rotated to orthographic views… we get another graphic indication of the roof pitch.
  • Like I said, I feel like a couple of measurements are necessary to get a reliable pitch calculation, so I just use whichever of these approaches are available to me.  Often, the calculated pitch together with the necessary roof frame(width of the rafters) will dictate what is spatially possible.  Time spent getting that correct is very well spent.