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andyf_gw

LSL Beams for Old Solid Hardwood Beamed Ceilings

18 years ago

The livingroom of my 1840 home spans 20 ft with no posts (originally an ancient post office/gen store on a stage run). The years have taken it's toll, and I have a sag in the original hardwood ceiling beams. They are of ash and measure 7in X 9in high. WE want to use the upstairs to make an open bedroom loft. The only framing that the loft will have is a walk in closet at one end and it will be 2 X 3's framing, with 3/8 gyproc on the outside, and 1/8in pre-finished panels on the inside to conserve weight. The rest is all open area. So there is hardly any dead load, as bedroom furniture is placed on the outside walls.

My Home Hardware recommends 2 TrusJoist(.com), LSL 1.7E beams measuring 5 1/2 X 11 3/4in high by 20ft. Each beam is a sandwich of 3, 1 3/4 X 11 3/4in high segments nailed and glued. They recommend I jack up the old beams in the center to take up the slack, (but just enough, as the old beams will never return to their original shape after these many years), then install the LSL, then slowly lower the weight onto the LSL breams. The LSL beams will be spaced approx 6 1/2ft apart, and support the old beams.

The only problem I see is hanging the beams, as the tin supports designed for new frame construction aren't practical for round log homes, and my wife doesn't want to see end posts in her living room. So I welded up 4 special saddle type hanger brackets of 3/16 plate, which will be lag bolted to the top logs of the wall with 1/2 X 5in in bolts, These brackets will suspend each end with double 3/4in threaded rod each side of the beam. I then can take up further slack by tightening the nuts evenly.

My concern is sag once again in the LSL beams. They tell me they are stable and will always hold their shape. I hope so with all the work I did in making the hangers. They say sag is 1/360 of the span, which makes it 6/8in., and I can live with that. Also the dimensions quoted are for 40lbs sq. Ft, which they say is sufficient for bedrooms.

Any thoughts or tips on this would be appreciated, as I'm nervous about the whole procedure. Having the work gang come in on Thursday to hoist them in place.

Andy

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