Main support beam replacement in basement

17 years ago

Upon renovating our basement we discovered that previous home owner had cut a 3 foot section out of the main support beam of our house to give more headroom for a doorway. They only used 6x6 wood posts to support the beam on either side of the cut. These posts are just resting on the cement ground (no footings). Obviously we need to have the beam replaced and yes, we have hired a structural engineer to give my contractor the specs required.

We are going to be installing a new steel i-beam with two steel posts to support it (with proper footings). I have two questions:

- how long does it take for the footings to cure?

- our basement is only 6'7" high and the new beam will be running the length of the house basically down the centre. To get as much headroom as possible, we'd like to have the new beam 'recessed' into the ceiling or 'flush mounted'. How do they do this? I know it will be much more expensive, but is the cost astronomical?

Thanks!

Featured Answer

architectbob

17 years ago

The process of flushing out a beam is relatively simple - we do it all the time in Chicago along with lowering basment slabs from 4" to 24" to pick up the additional head ht as you are seeking. It's smiply a matter of man-power and wasted materials. In short, 2 support walls need to be built to support the ex. joists on either side of the new beam line. Once in place, the joists should be cut to a close tolerance of the width of the new beam - just enough to allow the beam to fit in between. Once the beam is in place install and secure the support columns for the new beam. Then, using joist hangers, attach ex. joists to the new beam. This is a chance to "level" the floor above, should there be a "bowl" or "hill" in the floor. With a skilled group of carpenters and complete drawings from the engineer - its a 5 day or less job. Good luck.

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Comments (6)

GammyT
17 years ago
How long a footing takes to cure depends on where you live, the weather and all of sorts of things. Your structural engineer should be able to tell you and your contractor that.

Adding an I-beam it is space minus the height of the beam. I don't know how it could be recessed without major structure changes upstairs.
ericwi
17 years ago
Have you considered installing proper footings under the two posts that frame the doorway, and retaining your existing main support beam? You might want to discuss this possibility with the structural engineer.
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budaby
Original Author
17 years ago
Unfortunately that option will defeat the purpose of the reno. We're trying to create an open concept and if we did this, there would be three posts in the centre of the room about 3ft apart (the original and the added ones).

Does anyone know how they recess or flush mount an i-beam up into the joists vs. having the joists rest on top of the beam?
philmont_2006
17 years ago
Bud, To have the beam flush with your joists they use joist hangers made for steel beams. This is not a big job when I house is being built, but in an existing house it is a major deal and expense. I myself can't see me ever doing this for more headroom. Don't get me wrong I know every inch counts. But, there are a couple of things to ask you engineer. First, can you put some supports in the basement, this will effect how big your beam is going to be (depth). Also, there is are different weights of beams that you can get so you can get the shortest beam possible while still being able to carry the weight.
To replace the beam your contractor will need to put a temp. beam on each side of the existing with proper supports as well.
Oh, just thought of something,,, if you want the beam flush it would be easier to do with a microlam beam than steel, then all your joist hanger work can be from your basement. The microlam probably will be deeper than steel but easier to install.... I would look at both options. What is the size of the beam now? and also how far are long are the joists that this beam supports? I'm assuming you joists are 2x10's 16" o.c.
Thanks Dave
budaby
Original Author
17 years ago
I was starting to suspect it would be too much work. I'm definitely going to ask about the microlam beam though.

We're already planning on installing two new posts but they will be near either end of the room, hidden in new walls. The open area has a span of about 13'4". And yes, I believe the joists are as you mentioned.