The PDF I linked in this post for pham shows individual 1-3/4" only which is why I was originally doing the math and dividing by plys at an earlier time. What do you mean by loads are probably wrong unless it's really low attic space? Please share! Are you talking the 10PSF live load factor? I'm here to learn and make sure I - That was my mistake in typing late and mixing the PDF's. I am a little more familiar with this companies' tech sheet. I traditionally follow the LVL manufacturer specs for fastening them - I meant to link this ONE. RE: PLF Calcs for LVL Beam Luceid (Structural) 28 Apr 23 - Building LVL beam consisting of multiple 1-3/4" LVL sorry if plys was confusing there. I was considering using the percentage change from their roof PLF (240) to their floor PLF (360) and multiplying that ratio to the numbers but I'm sure that's just shooting in the dark. It seems too easy simple, and I'd also like to know of any quick formula perhaps to convert the PLF rating of the LVL for less deflection like L480 when their chart maxes on 360. and the first LVL to do 280 with 3 ply 14".Ĭan someone please tell me if this is the correct process, assuming I had a correct PSF to start with? I'm just looking for confirmation that I am not missing something here. When I comb through the chart, I locate 22' for the span and go across on the "Two 1-3/4" GP Lam LVL" (and three) to find the first LVL that can do 280 with 2 ply is a 16" LVL. I scroll down to the Allowable Uniform Floor Loads because it uses at least L/360 in this case since it is drywall that would be sagging here. In this case, the Georgia Pacific GP Lam LVL tech sheet has 1, 2, 3, and 4 plys already built in. I then divide this by 2 and 3 to find my individual PLF capacity needed for 2 and 3 ply of LVL EDIT:If using a chart for single 1-3/4" only. I'd say that is more than 10PSF but online searches seem to treat person in attic as 10PSF?įor the first part of this, I am taking 20PSF x 14' (half the 28') to get my PLF of 280. 5PSF for attic dead load of insulation and 2圆 framing (stick framed with rafters, ridge board, etc and not webbed truss), 5PSF for two layers of drywall/mud, and 10PSF for what would be live load of someone crawling around in attic. I was going to use 20PSF for this rating. The ceiling joists have 5/8" drywall - let's say 2 layers - and then attic space above with blow in insulation. The ceiling joists are for two rooms, each room for this example has a length of 14' so the "Span Carried" would be 28' but technically when I run the PSF I would halve this I assume? A LVL beam to be installed to support ceiling joists that are *not* continuous, as in they tie into the LVL beam. I believe this is the PLF rating? It seems a little too straightforward using the tech sheet so I want to make sure I am calculating correctly. I'm wanting to learn how to properly size an LVL beam when the specifics do not simply fall under the manufacture's generic span chart giving two options for premade spans. I didn't realize that the lumber yard could provide expert consultation in this way, so that suggestion was very helpful.Hey all. I'd love to lower the foundation, but at what expense? Going lower on the foundation would have meant double the drilling since now I'm exposing more ledge area and it's more solid. That got me an extra foot in the basement, to a 7' ceiling if I used 2x8's for joists. I spent a week drilling holes (130) in the ledge and pouring in Dexpan to break it up to the point where a small hammer on a skid steer could bust it out. Blasting is not an option due to cost, and I doubt that any demolition person would do that when it's right next to another structure. When we dug the hole, we hit ledge at 6 feet down. I may keep the 8" LVLs and use them to stiffen the floor in the older section.Īs for "refusing" to drop the foundation, or raising the floor: It would be better to say I'm having to make choices. This will still be much better than the house I'm adding on to where the floors are carried by 2x8's sitting on horizontal 4x4's resting on piers every 6 to 10 feet. He said that if I used a triple 12", then the floor would be perfectly stiff, but the double would be fine. Said that if I put in a center post, I could stay with the 8", but I don't want that. I dropped in on them this morning and after looking it over and doing some calculations, they said I needed to swap out my 8" LVLs for 12". I'm getting my materials from Hancock Lumber in Conway, NH.
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