- Q.When you remove
one rafter to install a skylight, do you have to double the two
rafters at the sides of the opening? What about the
A. When you’re framing
a skylight that requires you to remove no more than two
rafters, a common rule of thumb says to double the rafters on
either side of the opening and use double headers. This is
often required by building inspectors, but in fact, it’s
a very conservative guideline that often results in unnecessary
framing. Only in rare cases are the doubled headers required.
And in many cases, particularly when 2x10 or 2x12 rafters are
chosen for insulation thickness rather than for strength,
doubled rafters may not be required.
In my experience, the inspectors also often insist on joist
hangers at the headers, but these are also rarely needed.
Usually, an adequate number of 16d nails, as many as 8 nails
for a 2x12 connection, depending on the loads) can handle the
Watch out, though: As the opening size increases to the
point where you’re removing three or more rafters, even
doubling the perimeter framing may not be sufficient.—R.R.
structural requirements, it may be unnecessary to double
trimmer rafters. It would rarely be necessary to double the