I am working on a basement remodel project that requires installing some headers in a 26′ bearing wall, which supports the above single story floor load.
I had the beam sized by my lumber yard and it turns out using a double 9 1/2″ microlam beam, supported at 4 locations is the best solution for the project (most headroom and better load distribution to footings). The footings will need to be added as currently the wall only rests on the 4″ concrete slab. No problems so far, floor has been cut to move/add underground plumbing and to allow for the new footings.
Now to my question, how would you install this 26′ beam?
I’m thinking of supporting the floor joists on both sides with temp walls, removing only the portion of the existing wall necessary to install the new footings, then knock out the remaining existing wall.
I then jack the beam into place, install necessary support columns and framing and remove the temp walls.
This seems logical, but I have never done a span this large. Does anyone have any ideas for easier, faster, safer, or better???
Thanks in advance.
I didn’t know that the picture posted. Not the best angle but the bearing wall in question is behind and to the left of the ductwork.
Edited 10/13/2006 5:29 pm ET by vintage1
Replies
Cost out what it would take for you to do the temp walls, then ask a house mover to bid on doing the temp support for you. When something feels like too much of a stretch, consider subbing it to somebody who'd consider it an easy job.
-- J.S.
John,
It's a good point. I used to try to do everything on a project just to keep it in-house and try to control costs. I have since learned to sub things that I can't do efficiently.
I don't think I am stretching too far ( for me) on this one. I'm always looking for ideas to improve efficiency/safety.
I would just do the temp walls for support as you described. Usually the joists are lapped at the old wall and you need to shore on each side.
The typical approach is a bunch of 4x4s sitting on blocks and supporting temp 4x4 beams, and for what you describe you can probably put them on 4' centers (please note that I am not a structural engineer and I do not play one on TV). When I do shoring like this I use a bottle jack at each post location to lift the floor above slightly and get some weight on the post, while simultaneously unweighting the old wall.
The problem with this is that you buy a bunch of 4x4-8' and cut them down to a useless 7'+/-, and then have to store them later. A nice alternative is to rent post shores that are adjustable in height. There's an example in the opening photo here:
http://www.ellisok.com/ellisok/rescon.html
and there are lots of them that are all steel and use no lumber, like lally columns.
Generally, the sequence is move the beam into place on the floor right where it's going to go, then shore the floor and remove the old wall, pour concrete, wait for it to cure, raise the beam, install the posts, and get paid. The part about moving the beam first is critical, and don't ask how I know that.
John's idea of hiring a house mover is a good one. The last major thing I had to shore was a concrete driveway that spanned from the street to a house over a major ditch. I had some house movers support it while we replaced posts underneath. They came in with a bunch of cribbing, steel post shores, a small boom, and a portable welder and got the whole thing beefed up... I think they made about $5000 before lunch.
Vintage,
Would installing the new beam alongside the existing wall adversely affect the joist span or bearing length?
I have done a few jobs similiar, but most were using lumber floor joists or I joists.. I question where to put the temporary walls, since these are floor trusses, and a lot of the area is just a single 2 x 4 on flat.
I am not an engineer, just questioning whether a floor truss will stay together, if loaded somewhere other than the original load points. I have fixed some of these when they were installed wrong, and it wasn't pretty.
Greg in Connecticut
You get extra points for looking at the picture. Those ARE floor trusses. Nothing I said in my post applies.
Mostly trusses, but it sure looks like a bunch of I joists on the left side up there, too.
Is there a supporting wall above this on the first floor?
Cut a hole in the outside wall of the house and slide strongbacks in on ecah vertical member possible. Use the tallest 2x stock you can fit in the webs.
Then GRK the strongbacks to the vertical members. 2 per connection.
Are the trusses spliced over that wall?
Or are they one piece and the wall breaks up the span?
If they are spliced temporary walls will do it.
If not strongbacks.
95% of the the trusses are spliced over the bearing wall.
I am just catching the details now. I-joists for a sunken living room on one side and floor trusses on the other.
I would go with the temporary walls in this case. Leave enough space between the temp walls to work. A 26' beam and workers will clog a small area up in a hurry.
We'd simply build the temp walls since there won't be that much weight on any of it and forgo the jacks and whatnot. It really doesn't take that long to build 50' of 2x4 wall, especially since it doesn't have to be perfect.
I'd put the top plate at an intersection of the floor truss and measure for deflection between the top and bottom to ensure you aren't putting too much stress on anything. I'd be surprised if any of the loads would produce enough deflection to measure.
2x4s on single top/bottom plates and directly under the floor joists are more than strong enough for anything you're going to do.
Angling in your studs as you go should produce more than enough upward force to support the floor. A little candle wax on the moving end of the stud will reduce friction and allow more effective wedging action. Careful measurements from ground to floor joist will let you know when you're actually lifting the floor a bit. You might be surprised at how easy it takes weight off the existing load bearing wall.
The truss to the left of the stair appears to be continuous. The stairway framing is for sure cut and end-bearing on the stud wall. Ductwork will dictate where the temp wall can go. Bottle jacks, temp. columns or short walls could be used to shore the stair floor framing. Getting a 1-piece 2-ply member in here will not be easy. BTW, a 2-ply 9 1/2" lvl @ 26' L. is carrying some loads if your specs called for 4 columns (that would be a clear span of 6.5'). You may have to break the beam over the supports and do a section at a time?
Looking forward to how this works out for you.
Finn
Thanks for all the input.
To answer some of the above questions:
I can't put the beam next to the wall. I have floor trusses on one side and TJI's on the other (The TJI's allow a sunken living room on the main floor). Each system overlaps the wall which means the floor truss bearing point is directly over the 2x4 wall. If both sides were TJI's, I could do an "in deck" beam, trim the TJI's and hanger everything, but modifying the trusses seems like a non-starter.
There is no supporting wall above. As far as I can tell the roof trusses bear on the outside walls of the house, so we are only talking about floor load.
I plan to support the floor trusses with a temp. wall approx. 16" away from the existing bearing point on each side. Should I block the trusses to prevent compression,deflection, or damage at the temp. bearing point?
The calc's on the beam show approx. 1500# on the left side. Span 8', add a column to support 9000#. Span 10', add a column to support 9000#, span 8' to support 3500# on the right side. Each end can be supported by one trimmer stud. Steel columns aren't necessary, but it is cheap insurance, and allows design flexibility.
I can post photos of the process. If it goes well, the pictures might be boring, if not, it will be one for your scrapbook.
I take a job like this and sit down with a cup of coffee to ponder it for an hour or so on site.So don't take anytihing as gospel, but my impression is that I would build one temp wal immediately next to existing on the truss side, and the other back about 2-3 feet under the I-joist side.I might even consider seeing if theree is a way to build that I-joist side fiorst and then slide the existing wall over
Welcome to the Taunton University of Knowledge FHB Campus at Breaktime. where ... Excellence is its own reward!
"I plan to support the floor trusses with a temp. wall approx. 16" away from the existing bearing point on each side."
Floor trusses shouldn't be supported where there's no joint. You're a LOT better off going back the first bottom chord joint and supporting them there. Otherwise you risk damaging the bottom chord.
I'd also make sure the owners weren't home, so they don't walk around above bouncing things around.
I wouldn't suggest supporting the I-joists much more than 2' back from the bearing.
If you're 2' back on the i-joists and about 5' back on the floor trusses that should give ya plenty of room to work.
Doing the beam in sections sounds like a good idea to me. I haven't seen many basements where you could get a 26' piece of LVL into it anyway.
The Middle Eastern states aren't nations, they're quarrels with borders [PJ O'Rouke]
Boss,
Following your posts I know you are a truss guy, so I figure your the one to ask.
If I understand you correctly, it is better to be 3-4' away from the original bearing wall and put my supports under a splice plate where the 2x4 webs intersect, rather than 1' away supporting the bottom cord?
Would it make any difference if I blocked between the top and bottom cords with 2x4's?
I didn't say to support the truss at a splice plate - I said support it at a bottom chord joint. (Where the webs meet the bottom chord) That point is roughly 5' back from the end of the truss. There's a vertical web at that point, so adding blocks won't accomplish anything.If you don't follow what I'm getting at let me know and I'll post a sketch.
In an underdeveloped country don't drink the water. In a developed country don't breathe the air [Jonathan Raban]
Boss,
I follow you on the bottom chord joint location.
Regarding the blocking, I was asking if you could install blocking between the top and bottom chord closer to my existing bearing wall, and then install a temp wall under that location. Would that work, or are you better off having the trusses cantilevered 5' over the temp wall while I install the beam?
Thanks
Blocking between the top and bottom chords would not really accomlpish much. I'd suggest staying with a panel point.
You don't know anything about a woman until you meet her in court [Norman Mailer]
ok.
Temp wall framing begins tomorrow morning.
thanks
Thanks for all the advice I received.
I framed all my temp walls on Thurs. I used some of the suggestions posted earlier about supporting the trusses at a joint and was able to detach part of the existing wall and persuade it (sledgehammer) to one side, allowing the beam to be raised.
Footings were also poured on Thurs. 40 bags of concrete was just right for 2- 30"x30" and 2- 18"x18" footings.
Today I got the microlams in place, and used my wall jacks to raise them into place. Worked pretty well, beam was raised with all four supports installed by the end of the day.
Attached are a few photos. Sorry they are a little dark.
Thanks for the pix. All too often, we don't get to see how things discussed here actually turn out.
-- J.S.
John,
Yeah, this one seemed like a "garden variety" job most of the people here can easily do, but I thought a few pictures might show how I completed it.
Thanks for checking.
I'd cut a temp stud under each truss. I'd probably do it just as Piffin suggested: close to one side and leave about 4' area to work in.
I'd probably cut the microlams into 8.66' (26' divided by three spans = 8' 8") lengths and put them up in pieces. I'd buy six 10' micros and be done with it in a couple of hours.
blue
Our Skytrak is for sale. It has 500 hrs on it. We want 50k (you pay the freight) and we'll finance it. Drop me an email; it's a good buy.
I agree with blue on using shorter beams, I would add 24 inch strong ties on each side of each butt joint
orbs