I'm interested in knowing how one would go about replacing part of the
main beam (basement) of a 1926 house.
I've consulted a structural engineer to figure out the required size/
strength of the new beam (probably steel). He will also be specifying
the size of the required column and its footing. I'm currently trying
to figure out how the work can be accomplished and would appreciate
The beam to be replaced is made of 3 wooden 3x12. My issue is with the
fact that the floor joists are hanging from that beam (as opposed to
being supported by it). Sitting on this beam is also a 4-feet section
of a load-bearing wall.
I figured that I could support the floor joists with jack posts or
some temporary load-bearing wall on both sides of the existing beam,
but how can I support the 4-feet section of wall without being in the
way of the new beam to put in place?
Whatever I put in place there must be removed in order to put in the
new beam, but I can't put in the new beam without supporting that
wall... What kind of approach would you suggest to take here?
What's the engineer say since he has access to all the particulars?
I'm curious about why this is needed now in an 80+ yr dwelling. Unless
there's a definite need for replacement, I'd be more for simply adding
adequate hangers and _perhaps_ some additional support if it does have
some deflection issues in the beam itself.
As per usual, too little info from afar, particularly for structural
What is the 4 foot section of wall supporting, and can you unload that
section of wall? For example, if it is carrying ceiling joists, you
could build temporary walls directly above the temporary walls
carrying the floor joists.
If it aint broke, dont fix it.
What is the current configuation not doing that it should be doing?
Are floor joists doing their job?
Where is the house located? High winds? seismic?
My house was built in 1930 (SoCal) I have not had to mess with any of
the original work unless I was changing load paths, fixing dry rot or
1930's plumber damage.
Photos would help a lot; overall shots & closeups.
Why not ask the engineer? He can see it, we cannot. I'm not even going to
try to tell you because no matter how I read your post and no matter how
well you read my reply, there is a potential for serious error. I'd want to
see it in front of me. Ask the engineer or a good contractor.
I think some pictures or drawing are needed to get any useful advice
ouf of the newsgroup. Typically you build temporary walls or use jack
posts to take the load off. In the case of the wall you would need to
build one or two temporary walls along it. You may also need to nail
some cross pieces at the ends to keep it from falling thorugh when you
remove the 3x12 under it.
I do agree with some of the other posters, is it not possiel to repair
what you have? Or are you trying to get an uninterrupted span where
I'm guessing there must be some posts holding up these 3x12s?
Thanks for all the replies. I didn't provide enough information, so
I'll to give some more here. Please let me know if were still missing
The goal is not to repair, but to remove a column in the basement. I'd
like to have an uninterrupted span of 16 feet in the basement to use
as a family room.
The current situation is as follows: the beam is in 3 sections of 12
feet. It's currently supported by 3 columns: one at 8 feet, 16 feet
and 24 feet from the front wall. On the ground floor, the previous
owners made some modifications and removed part of the original load-
bearing wall. From the front wall: there is now a 4-feet section of
remaining wall, a 16 feet opening and 6.5 feet of wall. That opening
is supported by a steel beam with columns on either ends (approx 4
feet and 20 feet from the front wall).
Here's some amazing ASCII art that depicts the current situation. If
you look at this with a mono-spaced font (such as courier) it should
come out ok:
G ||||| |||||
B || | | | ||
- Legend -
U : Upper floor (roof left out)
G : Ground floor
B : Basement
- : existing beam
| : existing column
||: existing wall (load-bearing or foundation wall)
= : existing section of beam to be replaced
By replacing that section of beam, I can remove that first column and
only have a single one at 16 feet which is ok in regards to what's
I did look into another solution: move the 2 columns in the basement
directly under the columns on the ground floor: 4 feet and 20 feet.
Then place a re-enforcing steel plate to hold up the two sections of
wood beam. The engineer made those plans and made the specs of the
columns, footings and steel plate. The downside of this plan is that I
have to take down additional walls in the basement, the footings are
quite large (4x4x1) and I end up having 2 columns in the basement. So
I asked the engineer to look into a single-column solution to see if
this alternative plan is feasible and what are its downsides. I'll be
getting these plans in the next few days.
Obviously, I'll also be asking the engineer about how to support this
wall section and the floor joist. But I thought I could get some
insight here also.
The goal is to know how one goes about doing this before I call
contractors. I like being informed independently from the people that
will be doing the job, otherwise they could be doing some nasty stuff
and I wouldn't the wiser... I'm trying to stay out of trouble, not get
Some additional info:
House is located in very safe, non-seismic place of the world (lived
here 30 years, we've had 2 below 5)
No hurricanes or tornadoes have ever gone by
Ground is very dense
Neighbours are attached on both sides
Thanks for all the replies!
Support the floor joists with temporary walls or jack posts with beams
on top. Put a couple temporary walls on either side of the wall that
is on top of the 3x12. These can be pretty simple. Lag a couple
2x6's to the ends of the wall directly on top of the floor to support
it while the 3x12s are removed. It might hang from above but I
wouldn't take the chance. Remove the 3x12 and replace it. Since the
present beam is a 3x12 I'd also look at a 3x12 manufactured beam
instead of steel. It will be easier to reattach the floor joists.
And I suspect the manufactured beam can handle the 16' span. Your
engineer could tell you.
The current beam is 3 pieces of 3x12. I expect that the new beam will
be steel and that it will be 12 inches high to support the 16 feet
span. I don't know how wide it's going to be though (7 inches maybe?)
The current floor joists are attached to the current wood beam. That
is, the beam does not run *under* the joists; rather, the ends of the
joists are nailed to the beam. So if I remove the beam, there's
nothing directly under that 4 feet section of wall to support it.
That's what I'm trying to figure out: how do I support this wall while
I'm replacing the beam?
If the new beam is not as wide as the old one (say 7 inches instead of
9), I suppose I could use those 2 inches to support the wall on either
side. But an inch on either side seems pretty slim!
If the new beam is not as high (say 11 inches), then I thought I could
use some type of steel plate supported by jack posts on either side.
Then slide in the new beam and simply leave the steel plate there
after removing the posts.
Otherwise, I thought I'd need to raise the wall a little, but I'm not
sure I like this very much. Anybody do anything similar? What can I
expect by doing this?
I just realized I misunderstood your solution.
So you're proposing to support the ground-floor wall from the ground
floor itself. Interesting. This moves the weight of the wall on either
side which would be supported by the temporary walls (or posts) in the
There's a column in that wall that supports a 16 feet beam in the
ceiling there. I suppose that means that I'd have to support that beam
in a similar way, by making some temp walls on the ground floor that
would support this beam (and, while were at it the 4-feet section of
Could I support the 4-feet wall from its top instead of its ends? The
reason is that one end is not very reachable and the other is
obstructed by the column supporting the beam.
Alternate suggestion -- instead of trying to replace the whole thing,
why not ask what it would take in a steel plate bolted alongside the
existing beam to get the span? (I'd guess 1/2" would do it, but I
didn't try any calc's, that's just gut feel).
That would only require supporting the floor joists on one side, cutting
them back to allow sliding in the (predrilled judiciously :) ) plate
bolting it through the beam and attaching the joists. If carefully
measured, you could even have the hangers welded in the proper locations
and simply attach the joists instead of both directions in place...
$0.02, etc., ...
That's Plan A, or close to it at least. The steel plate has been
speced-out and requires some, as you say, judiciously placed brackets
for the joists. The downside is that the engineer didn't seem to think
that I could get the 16 feet span using this. When we discussed this
plan, we immediatly thought we needed to place the basement columns
under the gound-floor columns to get proper support. You're right
though, I should get him to check if we can get a 16 feet span using
the steel plates solution.
I'm having hard time thinking that's not feasible/adequate unless
there's a lot more going on here than a simple two-story. What's he say
is the limiting criterion, deflection or loading (stress)?
But, if the engineer's convinced the plate alone isn't enough, have a
lower flange welded to it -- either a wide leg angle or T. In essence a
channel w/o the upper flange that you really don't have need for.
In the extreme, one could even go the "U" but that would surely seem
overkill (again unles....).
W/O actual loadings, drawings, etc., hard to say.
We actually did not discuss the possibility of a 16 feet span with
steel plates only. So I can't say what his opinion is. But based on
his proposed solution, I figured he didn't think it was possible. I'll
have to chat with him to know for sure.
His proposed solution *is* a steel U. 40 inches long with 9 blots on
both ends. He says that a U is required due to the compression
constraints on top of the beam and the tension constraints on the
bottom. He seems to think that simply putting in plates is not
sufficient for proper support.
Keep in mind that the engineer is going with the safest solution here.
So it's probably somewhat overkill.
His proposed solution states that the columns (one a 4.5 feet and one
at 19.5 feet) both require material to support 25 000 pounds. So he
speced the columns as 5.25x5.5 PSL.
What other loads would you need to have a better idea? I can ask him
to give me the values.
It's true though that if the second column is at 16 feet instead of
20, then the first column might not be required if the steel U is
strong enough. I should've thought about that earlier!
Well, he ought to be making something adequate but minimal to do the
job, not over-designing; that's not engineering.
I'm totally confused now -- where did the 20' span come from? Your
objective stated up top was a 16-ft clear span for a family room. Yes,
a 20-ft span is going to cause the requirements to go up quadratically
to a first approximation on deflection which would be ~1.5X and linearly
on stress, though.
Oh, OK, I went back to your drawing and sketched it out on paper w/
dimensions. I see what he did was to automatically place his columns
under the upstairs walls to get the direct support transmitted
vertically. That's kewl...but what strikes me is that he doesn't need
additional beam to transmit that (locally distributed) point load; the
existing beam is (apprently) doing that fine w/o crushing so it will
continue to do so.
It would seem the only real function the additional structural member
has to do is to handle the distributed load across the longer gap which
shouldn't be that great it would seem.
It almost sounds like he's discounting the existing beam entirely owing,
I suppose, to the point I didn't catch early on of it being a 12-ft run
on 8-ft supports. I'm not going to second-guess the guy but I'd wonder
if it really is needed to actually get that full U section under the
existing beam at the outside end.
I see w/ that location of the two columns you do have roughly the 16-ft
open space; I'm just surprised since the bulk of the loading is on the
ends instead of distributed it requires so much heft. What's the
dimension on the U he's given, including thicknesses?
To do any calculation would require knowing all the loads assumed,
live/dead/additional code-required for the jurisdiction, etc. They
ought to be on the design documents if you have access to those but if
all you've contracted for is a design, that may not be part of the deal.
As others noted, it would be possible to rig up ways to get it there but
it does just seem pretty stout for the application from afar and w/o
actually doing any real numerics, of course... :)
Yes, moving the columns under the ones from the ground floor was
automatically considered. Turns out that the required footing is much
larger than I had expected, so I have to tear down a whole lot more
basement for this solution. This is why I'm looking for alternatives.
The additional member here is the steel piece?
So, the proposed steel piece is a U: its legs are 10 inches high, the
base is 9 inches wide and would run along 40 inches of the beam. It's
1/4 inch thick.
Since the beam is made of 3 sections of 12 feet, this piece is there
only to support the connection of 2 of those sections. The steel piece
would cover 20 inches on both sides of the split.
In my mind, the proposed columns (at 4.5 feet and 20 feet) are doing
all the work really since they're directly below the ones on the
I asked him to look into another solution that has only one column at
16 feet (instead of 2: one at 4 and 20). The reason is that this 16
feet span would better suit what's around it: more specifically, the
staircase. As mentioned above, a single column would have less impact
due to the size of the required footing.
Yes, the codes are on the drawing, but not the assumed loads. I can
get him to add these numbers I suppose.
I understand all the complexities involved here, so I'm not looking
for formal advice: that's why the engineer is working for me.
In your mind, a 16 feet span with steel support around the split at 12
feet, a proper column at 16 feet, w/ proper footing *could* handle
this? Again, not looking for formal advice, here, I just want to steer
my engineer in the proper direction. They don't come cheap!
Yeah. Seems like a much larger job than I really expected...
Indeed, that's where I was confused before...I had misunderstood and
thought this U was the full-length beam replacement and were trying to
figure out how to get it in place on one end. I couldn't figure out
how, since the main load was, as you say being carried by the columns
one needed anything anyways near that stout as the intermediate beam
between them. That it's a gusset plate I can go with at the dimensions.
But, that leaves me w/ the problem of not understanding what's the issue
in the installation I think.
No, I don't think that would work; what I was envisioning was a full
length side plate of (say) 1/2" x 10" bolted thru the existing beam to
handle the longer span w/ the upstairs load handled by the columns.
I thought your original proposal was to replace the existing beam in its
entirety and my suggestion was to leave it in place and rather than put
something underneath it over the existing column to trim the joists and
rehang them leaving the vertical primary support on the column.
I think there's still some talking past each other owing to each having
a vision but not a common set of drawings/concepts...
Always is when get an engineer involved... ;)
Altho I commend you for getting somebody to actually look at the
situation given the nontrivial nature of the loading distributions and
particularly that discontinuous beam that complicates things.
Good luck; knowing the guy didn't try to fit in a full-length U to
bridge the gap and claim it had a stress problem makes me feel much
better about his doings...I believe it for the 1/4"T short section to
hold the end moments; I wasn't so sure when presumed it was much heavier
material and full length. <vbg>
Yes, the main confusion comes from the fact that my original question
was not about this plan. I was asking about a different plan that I'm
considering due to the problems with this solution.
Plan 1: 2 columns (4 and 20 feet) under ground-floor columns with
steel U supporting the beam's gap
Plan 2: single column @ 16 feet with beam replacement. (this post was
about this plan)
Ideally, I'd have a single column @ 16 feet, but this doesn't seem
possible without replacing the beam.
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