Re: Snow load evaluation

[Lewis Gardner <lgardner@xxxxxxxxxxxxxxxxxxxxxxxxxx>]

L. M. Rappaport wrote:

> You could put stress gauges on the roof rafters, but you'd still have the
> problem of calibration.  There are just too many variables - rafter size, rafter
> spacing, decking, shingle material, water content of the snow, ice, etc - to be
> able to do this in advance.

I used to do something like this in my last garage.

That garage lacked a BIG A** beam to connect a hoist for lifting motors
and other big stuff. As a workaround I placed a 2" steel pipe across 5
roof trusses and connected the chain hoist to the mid point. Using a
tape measure I would check the deflection of the middle truss. As long
as it was less than .5" (20' span) I didn't worry.

If I were to attempt a similar snow load sensor I would measure the mid
span deflection of a rafter in the middle of the largest lowest pitched
section of the roof. There are no magic numbers to go by but over time
you might be able to get a feel for "well the snow in 07 deflected the
rafter .25" and the house didn't collapse" so this snowfall is not that
bad (yet)!

Just a thought...