Roof Felts

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Author Message Anonymous   Posted on Wednesday, February 02, 2005 - 02:23 pm:    What is the weight (15#, 30#, 90#, etc.) of Type I, II, III, & IV roof felts? David R. Combs, CSI, CCS, CCCA Senior Member Username: davidcombs Post Number: 23 Registered: 08-2004 Posted on Wednesday, February 02, 2005 - 03:55 pm:    Which ASTM designation would you be refering to? ASTM D 226 - Standard Specification for Asphalt-Saturated Organic Felt Used in Roofing and Waterproofing, only lists Type I and Type II. Type I is minimum 11.5 lbs / 100 sq ft. Type II is minimum 26 lbs / 100 sq ft. ASTM D 224 - Standard Specification for Smooth-Surfaced Asphalt Roll Roofing (Organic Felt), lists Types I, II, III, and IV. I: 39.8 lbs / 100 sq ft. II: 54.6 lbs III: 51.1 lbs IV: 39.8 lbs There are several other ASTM standards for other felt materials. Check out www.astm.org for additional information. Anonymous   Posted on Wednesday, February 02, 2005 - 04:37 pm:    The spec I'm trying to make sense of is a concrete roof tile spec with inorganic felts and that does not list the felt weight, but lists ASTM D 2178 Type IV (I presume this to be a 30# base sheet) and ASTM D 3909 (I presume this to be a 90# cap sheet). The Florida Building Code also does not list felt by weight but by base sheet of ASTM D226 Type II ( we know this to be 30#) and cap sheet of #74 ASTM D 249 (I was told this is 90# felt, but I can confirm). George A. Everding, AIA, CCS, CSI Senior Member Username: geverding Post Number: 19 Registered: 11-2004 Posted on Wednesday, February 02, 2005 - 06:02 pm:    At one time in our distant memory, I think that the so-called 15#, 30#, etc. felts actually did weigh 15 or 30 pounds per square (100/sf), like 235# asphalt (organic) shingles used to weigh 235 pounds per square. And the weight of those products was a pretty good indication of the degree of performance you would get. With the use of fiberglass and other inorganics, the weight per square of these products started to vary all over the place. With the variation of manufacturing process and the shift from organic to inorganic, shingle and felt weights ceased to be an accurate predictor of performance. At some point in time, 15# felt became #15 felt (fifteen pound became number fifteen), and I think that felt underlayments are still marketed using the # for number, not pound. The various ASTM designations give a much better indication of the durability of the products, however. And when you buy "#15 felt" from the roofing store (or look it up on the website), the appropriate ASTM designation should be on the label. David R. Combs, CSI, CCS, CCCA Senior Member Username: davidcombs Post Number: 24 Registered: 08-2004 Posted on Thursday, February 03, 2005 - 09:37 am:    ASTM D 2178 (asphalt glass felt) does not list a weight for Type III. Types IV and VI are both listed at 6.2 lbs / 100 sq.ft. There are no Types I, II, or V listed in the Standard. Types III and IV are perforated. --------------------------------- ASTM D 3909 (mineral-surfaced roll roofing) lists the product at minimum 63.2 lbs / 100 sq ft. ---------------------------------- And as near as I can tell, Mr. Everding appears to be correct: the # meant number, not pound. And my copy of ASTM D 226-97 (eight years old now) contains no reference to (no. or lb.) 15, 30, 90, etc. So the "number" designation was discontinued by ASTM least 8 years ago. I have a copy of a Project Manual I wrote back in 1992 (using MasterSpec) and it DOES use No. 15 and No. 30 designations in reference to roofing felt. So if the # ever meant "pound", it, too, was discontinued at least 13 years ago. David R. Combs, CSI, CCS, CCCA Senior Member Username: davidcombs Post Number: 25 Registered: 08-2004 Posted on Thursday, February 03, 2005 - 12:16 pm:    ASTM D 249 - dating back to 1989 - makes no mention of "#74" So that particular designation was discontinued at least 16 years ago. Type I and Type II are differentiated by the "minimum net mass of granule-surfaced portion" Type I is 74 lbs / 100 sq ft. Type II is 71.5 lbs / 100 sq ft. Minimum roll weight is listed as 83 lbs and 80.3 lbs, respectively. How this correlates to "90#" I have no idea. Shedd Glass, CSI, CCS (Unregistered Guest) Unregistered guest Posted on Friday, February 04, 2005 - 07:54 pm:    Anonymous, ASTM D224 was withdrawn in 2002, replaced by ASTM D6380. The ASTM web site overview page for D6380 mentions 3 classes (M,WS,& S) but makes not mention of "TYPES".