OT-reinforcing floor beam in house

My wife and I want to finish our basement this summer. One of the obstacles we must negotiate are the load bearing posts, which support the main beam, which, in turn, support the floor joists. We'd like to keep the basement fairly open with larger rooms, without having any support posts in the middle of the room.

Our house is 11 years old. The basement walls are poured concrete, the floor joists are 2X10's on 16" centers and span 25 feet across the width of basement.

There is a beam which runs the length of the basement and supports the floor joists. The beam is slightly off center (13'4" vs 11'4" from the walls). This beam is made of (engineered?) wood and looks like two 2X10's laminated together, except they are actually 1 3/4 x 9 1/2" and don't look like natural lumber. Total beam dimension is 3 1/2 x 9 1/2".

This beam is supported by 3" diameter steel posts that are screw adjustable for height. The posts are spaced every 93 to 98 inches apart, except for the end posts which are about 6' from the wall. I'm told each one of these posts sits upon a concrete "footing" and are not to be moved.

My questions are; can I remove a couple support posts. The posts I'd like to remove are not located consecutively and would result in unsupported spans of 14 and 16 feet.

What's the maximum span that my floor beam can support? Is it possible to increase the safe load bearing spans by adding (laminating) another 2x10 onto the main beam? There is room to do this and the pads on top of the posts are wide enough to support an extra 2x10. I could even add a large steel channel instead of lumber, if so advised.

As you can tell from my inadequate building terminology, I'm not a carpenter or an architect. We have a contractor coming over this Friday, however, we'd like a second opinion ahead of time. Any opinions, suggestions, or links are appreciated.

Thanks,

John

Whydont you just trim them out?

My father in law just did this at a house he was working on and it looks pretty nice.

I would be leary of removing supports.

My parents house is 150 years old, the beams are 8x8 hardwood...no supports.

Your have 4x10, most likely pine? I wouldn't do it.

-Jacob

Check some beam analysis tables like in the machinery handbook.

It should be clear that adding a laminated board will not come anywhere near replacing the strength lost by taking out every other post.

Look at some 10" S-type I-beam (NOT channel).

I've done a few jobs like the one you've described and there are various levels of complexity you can go to depending on the actual conditions. On one old house in Seattle I built temporary walls on either side of the main central beam and cut out all the joists down the center of the house and installed an i-beam the entire width of the house. I filled in the webs with wood and hung the joists from that. The entire ceiling was flush with no beams or posts.
For your application I'd consult an engineer and they can give you a quick assessment of the loads, connections, footings, etc. and tell you right away what to do. Most likely reinforcing the beam with another engineered beam glued and screwed to the sides would give adequate rigidity to span the distances you want.

Adding width to the beam is not a very good solution. Having a taller beam at the same width is more structurally sound, but that in itself may not satisfy the load design. There is more than having a beam support a load. Stiffness is very important to keep the floor above from sagging excessively. You might be able to replace it with an steel I-beam, however that would be very costly. In any case you need to have an architect or engineer to look at the beam and the load it supports to determine if a longer unsupported span using a different beam or design is advisable.

Bottom line, DO NOT REMOVE any supporting columns or you may have nothing but problems.

Good advice given by others - You do not mention how much basement floor to ceiling joist height there is. If it is more than 8'or at least that much, you have some latitude to add to the depth of the support beam, while still having adequate head room. There is probably a reason why the support beam is slightly off center in the room. If you look at the overall house construction, you will probably find that there is a load concentrated at that point on the floor above the beam. However, it is possible that the ceiling joist are that length because 25' does not divide evenly using standard dimensional lumber.

one of the problems with this type of Q is that we who post answers may not be technical types and don't want to incur a liability situation either for you (I.e.,find out your insurance is void in the event of a claim) or ourselves (obvious)

I have done this a number of ways, listed below. On my own property or relatives, i run some calculations using tables in steel books, machinery's, and published strengths of lumber. In some cases for close friends, i do some rough calculations and then vastly over-build. For customers, I draw it up and run it by an engineer.

In new construction, a quick, common way to get extra span for a given limited depth wooden beam is often attained by a "fiche plate" between the wooden layers. This might be a piece of 1/2 x 10 A36 steel bolted between 2, 2 x 12's. The number, diameter and spacing of the bolts is called out in the plans and must be adhered to.
In your case, it might be that an engineer could verify if a 1/2 x 9" or 10" fiche plate on each side of your existing beam, bolted through on a specific schedule, could attain the span you want with the loading and deflection required in your code. An alternative might be 2, 10" wide channels bolted through.

I have jacked up joists, removed the existing wooden built up beam, and slid in a new steel W section sized to conform for the expected loading and deflection. You will need to fasten the top at each joist on a specific schedule to attain the espected performance and safety.

There have been a number of cases where people wanted large open spans below, where maybe they want to remove a lot of existing walls and create one large open space with a dramatic span. Sometimes in putting on an addition, the customer wants a very wide opening in what was previously the outside wall, without reducing the height by putting in a deep beam. This can be surprisingly easy to accomplish with a diaphragm/stressed skin sheer wall built above.

In some cases, a wall is built above where the main support wall used to run below, all the joists are hung from the upper wall members with mechanical hangers, and the entire wall is sheathed with plywood (thickness to suit application) glued with epoxy and screwed down to every stud and plate. In some cases the inside of the wall may have diagonal braces included. Everything is glued and screwed between the plywood. This wall acts as a very tall beam and can provide tremendous stiffness and load carrying. It can even be designed with opeinings, such as doors, if the sheer wall will be part of a living space. In this case it will be sheet rocked over. A major caution is that no trades ever ruin the integrity by cutting for electric, HVAV, or plumbing without consulting the designer. Also, end support for the sheer wall will no doubt need to be addressed by reinforcement for crush issues at the ends, and extra columns at the end points, all the way down to sometimes new reinforced pads dug for footings.

There are lots of options, most of them not too expensive if you can do the work yourself. But I would run it by an PE engineer. Cheap advice in most areas, and they will often make sugggestions that can save you money or problems.

smt

[ 05-24-2005, 01:57 PM: Message edited by: stephen thomas ]

My house was built about 4 years ago (1900 sq ft Colonial), and when we bought it it was partially built. The larger side of the basement is about 20 feet wide, and the beam is (4) 2x10s or 2x12s. There was a column at each end and 2 in the middle. We planned on putting a pool table down there so we wanted to remove the middle columns. For $1200, they bolted a thick steel C-channel to each side of the beam and took out the columns. So far so good.

It's probably too early to tell how well it will hold up over the years, but the builder claimed that it cost so much (I didn't think $1200 was that bad) because they had to pay an engineer to design it, so hopefully it will be OK.

John

Your 2 x 10 joists are good for about 14 foot span, IIRC, with normal floor loading. So they are OK.

There may be a wall located above the double beam. That would account for its location.

If your posts are 93 inches apart, that is just shy of 8 feet. Taking one out would leave therefore a space af nearly 16 feet, as you say.

If a normal floor load requires no more than a 14 foot span, why would you expect that this double beam, made of what are basically 2 x 10s, would span 16?

That is not to mention that it carries more load because in that span it is holding 1/2 the load from a dozen or so joists, plus whatever load is coming on it from above.

You would have to make that beam deeper. It could be done, with some form of engineered lumber. But you'd have a lot of structural work, need an engineer, and permits etc.

I believe I'd live with it.

BTW, most of the requirements are based on deflection, not collapse. Too much span, and you will be popping drywall if several people stand in the wrong place.

Thanks for all your replies. IIRC, several months ago there was a long thread about I-beams and gantry cranes, so I knew there was plenty of expertise here.

I asked the questions mainly to determine feasibility. Your responses generally supported my gut feeling that it would be far more work and expense than we want to do.
If our contractor were to say something like, "you know, for a couple grand, you could do.....", we'd probably go for it. However, I don't expect to accomplish this for less than a few thousand $, so we will most likely keep all the posts and trim them out as Jacob suggested.

John

First of all my experience with concrete footings instead of a proper foundation is that they usually are inadequate to start with. I've never met a footing that didn't move and the longer the time span, the more it will move. If the water table ever reaches the footings (in a flood year, eg) they will move a lot. When the footings move the beam will begin to warp. Eventually the warping will spread to floors and walls.

With a bunch of different footings as here the effects are masked because the multiple footings distribute the load. Eight feet between columns is long way for wood.

What you have is probably "LVL" (=laminated veneer lumber). Unfortunately this can be made in a range of different strengths, so unless you get the specification from the builder there is no way to know just how strong it is. However, you can bet that there is not a whole lot of over engineering there. Removing a column is highly inadvisable.

If you put in a steel arch you need to put down new, heavier footings which will be mucho expensivo. Not only that but as I said above, the footing designs engineers use nowadays are not even close to 100-year designs. They are like 25-year designs. If I was putting in new footings for some thing like this I would take the engineers recommendation and TRIPLE it. Otherwise after 100 years the house will look like a sofa. If you get a quote for a 3 x 8 foot concrete footing you will say, "Man, I could have bought a house with a foundation for that kind of money." Right.

JohnnyJ-

You're talking about a currently unfinished basement, right?

It all boils down to how much information you have. If you still have or can access the original plans showing the column pads for your house, and the structural layout, it would not take long for a civil engineer familiar with the soil, "common practice," and codes in your area to tell you whether a couple channels bolted on each side of the existing header would allow you to take out one column, or whether a W section could be substituted. Also whether the end columns would need partnered, and perhaps a spec for welding them and lagging them, dimensions of the plates on each end, etc.

If you have plans of your house for the engineer to review, or can reconstruct them, and can set forth the plan of attack with an engineers stamp on it ($250 - $500 if you draw it up) and simply hire the contractor to execute it, i don't see a lot of money involved. $300 for steel, a bunch of bolts, maybe 2 extra columns with welded ends, assume a window to slide the beam in, and labor for 2 guys for a day + a days overhead to organize for it.

It is possible that with the soil in your area, the existing pads won't be up to it, as someone else mentioned. But i think I would want to find that out by asking someone familiar with your area. If you are on shale or bedrock, it won't be a big issue. If you are on something else, maybe it won't be possible. What i am trying to say is that like any project, the more information you have, the better your decision making process is going to be. If the project is feasible on the existing footers, i don't see a lot of money involved. But you have to do the legwork.

smt

I am assuming you are on sand here.

There is another option besides a U-arch. That is to make a cross lintel:

</font><blockquote>code:</font><hr /><pre style="font-size:x-small; font-family: monospace;">
[joists not shown]
F1
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===A====B====C====D====E====F====G===
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F2</pre>[/QUOTE]So in the diagram above your goal is to remove column D. There is 8 feet between columns. By removing D and putting in a cross lintel you have an open 16-foot square for your pool table or whatever.

You will need to add two more footings, F1 and F2. This will be cheaper than try to improve the footings of C and E to support a sistering U-arch.

The cross lintel itself will need to be steel.

Where I live, you would need a building permit to remodel the basement. The city building inspectors would get real nervous with what you are proposing and want a drawing signed by a registered Professional Engineer before they apporoved the permit.

They got that way a few years ago after a couple of new houses slid down the hill after a rain storm and the city was also named in the many lawsuits since they approved the construction.

Most structural steel fabricators employ one or more registered structural engineers. If you make up a sketch and tell them what you told us here, plus interior wall construction, # of stories above the basement, etc, a structural guy will size a couple of channels to scab onto the existing beam in less than 15 minutes. These people work to get the steel sales and fabrication work, and not to generate exhorbitant fees like a lot of consultant PE's do today. So, you can get it sized, detailed, and fabricated all in one stop. Also, most all structural fabricators have a good list of folks with 2 or 3 guys per company who do small erection jobs and such, because they're often subbing work to guys like this on stuff they fabricate. Two men can easily do the job you're talking about in an unfinished basement in a day's time and have plenty of beer drinking time left over. They might use 3 men so 2 can hustle the channel into place and the 3rd can get it clamped off. Either way, the job isn't a major undertaking. The entire job should run less than $2000 if you approach it like this. J Lauffer mentioned his cost $1200, which sounds reasonable for 4 years ago. The cost of steel and higher vehicle operating costs for people who do field work would probably put the same job around $1500-$1600 today.

Bottom line: Its easily do-able and not nearly as complicated as some people might make it sound. If you look at the section modulus of back to back steel channels as compared to a micro-lam or some similar engineered wood member, my gut feeling is that your 16' span with the two combined will have less midspan deflection than the micro-lams have now at the center of their 8' spans. As someone else mentioned, things like this are sized based on max deflection, and steel is some seriously stiff stuff as compared to wood.

Avoid getting any city or county inspection bozos involved in this and you're life (and the job) will go much smoother. In the case of roughly 99% of these clowns, if they actually had any knowledge or ability they wouldn't be working for inspector's wages. They rarely are capable of any constructive advice, but a bunch of them are very capable of being an ignorant pain in the ass.

Watch out....the steel fab folks may not be very good....

Buddy of mine had a 20 x 40 roof to put up, and got the steel fab place to figure out a beam for the unsupported 20 dimension at the peak. They came up with a beam 6 or 8 inches high.

When I checked, I found that it wouldn't have *collapsed*, but it had a lot of deflection, at least 2 or 3 inches, which would have popped drywall.

He asked me to check, because he and his carpenter foreman didn't like the "look" of it. I'm not a structural engineer, but I do know something, and have had structures courses. I found he would need a 12" for that, based on snow load and teh area supported. He eventually went with a deep microlam, which will be better all around.

The steel guys would have messed him up.

If you use a fabricator who employs a registered structural engineer on staff, your chances of ending up with the proper steel are much better than they are if you walk thru the yellow pages and pick a "consultant engineer" at random. That PE might be a ME or a EE or a ChemE or whatever, because the licensing requirements unfortunately do not restrict a PE to practice solely in areas where he supposedly has some education and expertise. Thats the way it is here in NC, and I assume its pretty much the same anywhere in the country since most all states have reciprocal licensing agreements with each other.

For a uniformly distributed load on a simply supported beam, if you double the span (distance between supports) the bending stress in the beam is quadrupled. This means that framing at least three times as strong as the original beam must be added to support the load. But, the deflection must also be considered. When the span is doubled the deflection (sag caused by the load on the beam) is 16 times as great as the original case. So, if you quadrupled the strength of the beam based on strength requirements you'd still have four times the deflection as you had originally.

Running a few calculations based on the information you provided I find that one C9x13.4 (9" channel @ 13.4 lb./ft.) has about three times the beam strength as your 3.5x9.5 laminated beam. Two channels together with your beam would give you seven times the original beam strength. The ratio of deflection to span would be almost the same as it was previously. These channels would have to be continuous from one support column to the next, and they would have to be securely bolted to the wooden beam. You'd probably need a 1/2" bolt through both channels and the wooden beam every 24" near the top and bottom. (16 bolts in a 16 ft. span)

If your contractor suggests anything less than this make sure he will guarantee it.

Bill

You guys have given me plenty to think about. Our basement is unfinished. However, all the furnace ducting runs along one side of the main beam, leaving only one side of the beam accessible.

We inherited some building plans when we bought the place five years ago. Hmmm, I wonder where they went to?

My take-up from your replies is that the question is still worth asking to my contractor. I will require that what ever plans he might propose be reviewed and approved of by someone with the education and experience (building codes, structures, soil conditions, etc.) to know what they are talking about. It must be done right or not at all, I just don't like doing things half-assed.

I'm sure the qoute for the entire basement finishing project will be sufficient motivation for me to want to do all of it myself. However, we want to have it finished by the end of this summer. If I did it, it might be done by the end of summer '06.
My wife and I (She's 38, I'm 40) are expecting our first child Sept 1. I'd rather be spending my free time playing with our daughter than working on and cursing at the basement.

Sometimes it's best to do what you do best to make money and pay someone else to do what they do best to earn their money. Isn't that what helps make the world go around?

Thanks again for all your help.

John

Oh well,had you a very nice,thought out response and computer ate it...........you need to consult a structural engineer.Best of luck,BW