|Posted on Friday, July 09, 2004 - 09:25 am: ||
I am half way through a slate replacement on a house which had an original slate roof built in 1927. The original slate was 22" X 11" 3/16" thick. My replacements are 20" X 10" 3/16" but the new seem to vary up to to 1/4" inch. My roof is "L" shaped and I begin on the left side of the "L". I noticed the rafters were drooping about 1'4" over the length of a 4' level. I put the level on the rafters running down the opposite side and they are straight. My rafters are 5.5" by 1.75" and look in good shape. There are horizontal braces running about 7ft above my head in the walk in attic and also 'knees' along the floor supporting the rafters about three feet back from the lower ends of the rafters. I cut and old slate down to the 10" by 20" size and weighed them both. Old = 4.25lbs and the new were 5.25lbs. I didn't check for the drooping before I ripped the old roof off, but I am concerned I am overloading the rafters, especially in the snow belt of Cortland, N.Y. Should I be concerned enough to halt and try to get thinner slates or is this normal and probably something I just didn't notice before I began??
|Posted on Monday, July 12, 2004 - 12:02 pm: ||
The difference in slate is insignificant and should not be a problem. If there is 1/4" deflection in the rafters, it was probably there before you took off the original roof.