Creating Open Layout in Basement: LVL Joists vs Steel Beam vs LVL Beam
MacoBuilds
| Posted in Construction Techniques on
I’m planning to renovate the basement of my attached, 3 story townhouse. My goal is to create an open layout room in the back third of the basement. The building was built 100 years ago and is 20×60 ft. The first floor (basement ceiling) is supported by 2×8” joists (rough sawn, true dimensional) that run perpendicular to the length of the building, spaced 16” oc. These rest on thick sidewalls made of rubble stone. They also rest on a 6×8” beam (rough sawn, true dimensional) that runs down the center of the building. The beam is pocketed into the front & back walls of the building and is supported by steel posts . Starting from the front of the building, the posts are spaced about 5.5 ft apart. But the last post is about 15 feet away from the back wall. The back section of the beam is supported by a cinder block wall which is part of the existing boiler room.
I aim to relocate the boiler room, and remove the beam, posts, and cinderblock walls in the back 20 feet of the house. An architect I spoke with told me the beam and posts are load stiffening, not load bearing. But the support lost by removing them will need to be replaced. After 100 years, I see no defection in the basement ceiling and I would like to keep it that way. I’d also like to preserve as much headroom as possible down there.
It seems like there are a few ways to approach this and I am wondering if anyone here has any experience or advice with any of these methods. Because of the thickness of the sidewalls, the joist span (width of the room) I am trying to support is 18 feet. The length of the room (part of beam I am removing) Is 20 ft.
Method 1: (Architect recommendation) Sister the existing joists with 1 3/4 x 9 1/4 LVLs (i.e. Boise Cascade Versa-LAMs). This seems like a relatively clean solution, but I do wonder how well this would hold up compared to the existing beam, posts, and cinder block wall.
Method 2. Replace the section of wood beam with a 20 ft steel beam. I’m not sure the exact size of the beam that would be needed yet, but it would definitely cut into the head room.
Method 3. Replace the section of wood beam with a recessed LVL beam. This would entail making temporary walls, cutting out the middle sections of the existing joists, fitting the new LVL beam between them, and then attaching the cut ends of the joists to the side of the new beam with joist hangers. If I’m reading the tables correctly, this LVL beam would have to be at least 7 x 18” to span 20 ft. I’m guessing that is larger than the steel beam that would be needed, but it would also be recessed 8” so likely would cut into headroom less. It would also be a lot easier to work with than a steel beam. But doesn’t this put a lot of weight on the joist hangers?
Maybe there are other methods I haven’t thought of. Any advice would be appreciated.
Replies
Following this thread. Have similar situation where I'm dropping floor / underpinning foundation 2' in a 25x36 basement with 4-ply 2x8 main beam with 3 columns -- want to reduct to one or two columns. Had not considered the glulam sistering option, but looking to engineer for steel I-beam vs LVL beam.
PhilipP, Here is someone who made their joists from 3.5 x 9.25 LVLs to span 20'
https://www.youtube.com/watch?v=3LMyZ_r4pWM&list=PLp28qnwxAXpiNJK7I9S5OJH10f2au0GFc&index=10&t=117s