Step 4
Table R802.5.1(4) indicates the rafter spans for ground snow loads of 50 psf or less where
the ceiling is not attached to the rafters.
Table R802.5.1(6) indicates the rafter spans for ground snow loads of 50 psf or less where
the ceiling is attached to the rafters.
On both tables, footnote a. requires adjustment of the allowable spans if ceiling joists are
located at a point higher than the point where the rafters are supported on the wall.

Example 1
Ceiling not attached to rafters, rafter spacing 16 inches, Douglas Fir SS, 2 x 10 rafter size.
Table R802.5.1(4) indicates a maximum rafter span of 19' 5" with a dead load of 10 psf and
a maximum rafter span of 17' 11" with a dead load of 20 psf.

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Determining Snow Loads and Rafter Spans
 Using the Residential Code of New York State

Step 1
Using Figure R301.2(5), find the ground snow load for your area.
Our examples will be based on a house in the suburban Syracuse area.
Using the figure below we see that the ground snow load is 50.

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Step 2
Section R301.2.3 states that wood frame construction, cold-formed steel framed construction
and masonry and concrete construction in regions with ground snow loads 70 psf or less
shall be in accordance with Chapter 5, Chapter 6 and Chapter 8. Buildings in regions with
ground snow loads greater than 70 psf shall be designed in accordance with accepted
engineering practice and ASCE 7.

Section R301.6 states that the roof shall be designed for the live load indicated in table R301.6
or the snow load indicated in Table R301.2(5), whichever is greater.

Section R301.7 states that the allowable deflection of any structural member under live load
listed in sections R301.5 and R301.6 shall not exceed the values in Table R301.7.

Example 2
Ceiling attached to rafters, rafter spacing 16 inches, Southern Pine SS, 2 x 10 rafter size.
Table R802.5.1(4) indicates a maximum rafter span of 18' 5" with a dead load of 10 psf and
a maximum rafter span of 17' 11" with a dead load of 20 psf.

Step 3
Section R802.5 states that spans for rafters shall be in accordance with Tables R802.5.1(1)
through Tables R802.5.1(8) and that the span of each rafter shall be measured along
the horizontal projection of the rafter.