Hello,

I am wondering if any of the knowledgeable builders here know about roof load cobe.  I have a fairly new home (built in 2005) with rafters.  Wondering what the standard Ontario building code asks for in terms of snow (or anything else) load...?  I currently have about 12 inches of snow on the roof, and wondering if I should pay someone to come and clear it out...how much is too much?  I heard some roofs are built with 20PSF load in mind, but that seems quite low for heavy snow falls we get here.
We're expected to get 40cm tonight and tomorrow....will that cause my roof to cave in?

Thanks,
Patrick

Here's what I know. Water weighs 62.4 lbs per cubic foot. So if you had 12 inches of water sitting in a 12 inch square container, this is what you would have in one sqft. One inch then equals 5.2 lbs. That said, with snow you have a range of water amounts. Anywhere, on average, from 8:1 to 20:1 snow inches to water inches depending on how wet the snow is. 13:1 is an average estimate. If you have an average snow then you have apprximately 5.2 lbs/sqft well below your 20lb/sqft. Again, the range 8-20:1 could be worse or better depending on the snow condition, but again this an average range.

Check this site out: LINK

Hope this helps.

Bill

I can almost promise you that your roof wasn't designed for just 20 PSF, pending your location in Ontario it could be somewhere between 52 and 80 PSF for central Ontario. This also includes the wieght of the plywood and shingles as well, bottom line, you should be good for 3 feet or so +/-

If it was built in 05, you should be able to go back to the AHU and review the submitted drawings for your local accepted code. Your building official should know this immediately, but the plans may indicate even higher designs. even the builder may have a set of plans for the house you could have for record.