And at the same time, fibers stretch along the bottom edge. As a beam bends the outermost (extreme) fibers are compressed along the top edge. Loads cause beams, joists and rafters to bend. See Allowable Property Values | West Coast Lumber Inspection Bureauį b value or extreme fiber stress in bending. 2 Douglas Fir has an E value 1,600,000 psi 1 Douglas Fir has an E value 1,700,000 psi He said it's possible the grade is stamped on the lumber. California probably used No 2 Douglas Fir. The local lumber company said a 50 year old home here in N. For example: No.2 grade eastern white pine has an E value of 1,100,000 and No.2 hem-fir has an E value of 1,300,000. A material with a higher E value is stiffer. E is a ratio that relates the amount a given load causes a material to deform. For example: a floor joist appropriately selected to span 10 feet with an L/360 limit will deflect no more than 120"/360 = 1/3 inch under maximum design loads.īedrooms and habitable attic floors L/360 & 30 psfĪttic floors with limited storage L/240 & 20 psf.Į value or modulus of elasticity of the individual elements. They are expressed as a fraction clear span in inches (L) or ( ℓ) over a given number. Maximum deflection limits are set by building codes. If a floor is strong enough to avoid breaking but not stiff enough, it mayįlex under load causing a plaster ceiling below to crack. Strength and stiffness are the main criteria in determining load capacity. Since it is possible to use the attic for storage, the live load of the attic floor Placing heavy objects at the ends will not put as much stress on the joists as weight in the middle.įurniture, appliance, pelople, wind, snow etc. Of course it depends on how you place things. Lbs) and acceptable sag (deflection) by type of lumber. Then the tables (e.g below) show maximum span for a given weight (10, 20, 30. I had to look at tables for modulus of elasticity for No. There are no automatic calculators on the web. The formula to compute weight from span and construction type is very complicated. 6 hours later I think I have a rough idea. 2圆s on 16" centers and span e.g.12 ft which would tell me how much weight it would hold. I thought I could go to the Internet and find a table tha given the type of joistsĮ.g. (No basements in California) so thought I should see how much it would hold. I just put plywood on the floor of the attic of the California home where I'm moving. My brother put too much stuff in the attic over his garage and cracked a beam. The information below is primarily for floor and ceiling joists. Overview | Terms | Span Table | Values for Douglas Fir | Material dead weight | Links Building loads - Span Tables for Joists and Rafters Don's Home Home - Garden Building loads Contact
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |