15 lb felt is all you need.
15# felt is about .030 and 30# felt is about .062..
Most people just put 15-lb roofing felt under it.
When talking roofing materials. A square is considered a 10'x10' area or a 100 square feet. So you have 1,900 square feet. There are two basic types of felt: 15lb and 30lb felt. 15lb felt covers 4 sq= Total needed will be 5 rolls 30lb felt covers 2 sq= Total needed will be 10 rolls (*note, 30lb is more thick and better for your roof.
40 lb is equal to 640 oz because 1 lb is equivalent to 16 oz. Therefore, multiplying 40 lb by 16 oz gives you 640 oz.
53.33%
approximately 1000 nails 1-1/4
4 lb is BIGGER. There are 16 ozs in a pound, so 40 oz = 2.5 lb, which is SMALLER than 4 lb.
the best reason i can think of is the 30lb felt is denser and when applied over and uneven, older pine roof boards or plywood the density would be able to cover blemishes in the sub roof. Splinters from old nail removal, or other slight imperfections. Ice guard as used in freeze areas is also more durable to puncture...The need to lay the 30lb felt with little or no wrinkles also makes for smooth runoff. the use of correct material is important when the pitch of the roof is reduced hope this helps. jerome
40 st = 560 lb
it depends on the shingles, regelar 3 tab shingles use 15 lb felt, archatectual requires 30 lb felt and sheet metal requires 30 lb felt. but always check on the shingle package and your local building codes for specs
100 lb paper typically has a thickness of around 0.13 millimeters or 0.005 inches.