I built a 20' beam by sandwiching plywood and 2x10s. I alternated 3 layers of 1/2" plywood and 2 2x10s - so plywood, 2x10, plywood, 2x10, plywood. I glued them, clamped them and screwed them all together. I let the glue dry for 24 hours. If I prop up both ends and have two adults stand in the center (about 300 lbs total), it sags less than 1/2 inch. This will be supporting just the ceiling joists, sheetrock and insulation with nothing else. Do you think this is sufficient for a beam?
20' beam
- Thread starter sbrandt
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youngmotivatedengineer
Well-known member
More information is needed to evaluate the beam. What is the span of the floor joists connecting to each side of the beam. Is the beam simply in the middle of the floor,at the end of a deck, or is there a load bearing wall above that adds weight directly to the beam? What type of area is the beam supporting? Your design loads on the 1st floor of a house and usually higher than the 2nd floor. They same goes for a deck. Plywood usually adds minimal load capacity to the beam. In traditional house framing, plywood is usually sandwiched between two 2x joists so that the width of the assembly is equivalent to that of a 2x4 wall stud and you have flush surfaceto secure your sheeting and drywall. When additional structural integrity is needed between the 2x,they usually use a steel plate.
Agreed, adding plywood for a flitch beam provides MINIMAL extra capacity. It kills me when contractors refuse to accept this answer. Aside from that, provide the info requested above and we will review. Where are the spices in the plywood? Are the 2x10 continuous? Maybe finish a plan sketch of the construction and load layout.....
youngmotivatedengineer
Well-known member
Plywood between the 2x was popular with 2x4 wall framing so that the installed header would be the same thickness as the wall framing.
