Beam span calculator

Greg K · Jan 3, 2017

Since I have no experience at all with calculating such a number I thought I would check here. In my basement there are three 2?10 nailed together to make a beam to support the floor joists. The span is 25' between the concrete walls. Currently there are 2 support poles to help it carry the span. If I were to replace the 2?10's with a steel I beam so that I could get rid of the posts, how big would it have to be? The house is a ranch style, built in 75, the kitchen is above the beam area. What other factors do I need to consider?

Waterloo · Jan 3, 2017

Greg, I do not have a method of calculating the span and load requirements you are requesting. However, I have the same span in my house over a garage area. The span is 28 feet from support location to support location with floor joist spanning 25 feet overlapping on a steel beam. When I built the house I had a lumber company figure the span for floor trusses and than provided the proposed steel beam to be figured. The lumber company called back and stated the 12 X 6 x 21 pound per foot steel beam with 2 X 12 floor joist on 18" centers exceeded the specs they could provided with floor trusses. The kitchen above the garage has a large island in the center of the room including the cook top, dishwasher, sink, wine cooler and rock front bar area. I have lived in the house for 15 years with no problems.

tomturkey · Jan 3, 2017

I believe you will need to figure the loading in order to size a steel wide flange beam. In order to get the span with the existing load, it may be taller than you would like, cutting down your head room. Sorry I can't give any numbers just "free' thoughts. gobble

ed will · Jan 3, 2017

Hi, similar situation. When I was in the drainage business some times I would get a job without a plan. There was an engineering firm that I could phone and they would tell me what size pipe and schedule , how far between catch basins etc. They would charge a reasonable fee and give me a letter of their suggestions. I could use that when I got inspection. Maybe you should try that for your beam. Could be valuable for insurance purposes. Maybe your town engineer could help you there. Sorry for long wind! Ed Will Oliver BC

GordoSD · Jan 3, 2017

What load can that triple 2x10 support?

Tom in TN · Jan 3, 2017

Greg,

I have a good friend who is a civil engineer. His specialty is structural engineering and he has the additional credentials to be a Professional Engineer. Your challenge is exactly what he does for a living. If you are seriously looking to replace that wooden beam, you would be very well served to pony up a couple of hundred dollars to have a PE look at the loading and calculate exactly what metal beam you would need to replace your wooden one. I wish that you lived nearby. My friend would do that job for you in a couple of hours.

Tom in TN

Janicholson · Jan 3, 2017

Much depends on the loads applied to the first floor. The methods of construction of the roof and load bearing walls applying point loading to the beam in question are very relevant. A house my dad built has a 27 foot clear span in the basement. There are two 12"X6" WF 18 pounds/ft beams spanning the distance. they were arched at 3/4" from end to end and sit on rebar and grout filled block Pilasters on each end. The roof is conventional and has load bearing walls on the interior. We pulled a string on the beams after completion and before rocking the ceiling, and they were arched 1/16th inch. Jim

dpendzic · Jan 3, 2017

Greg--I agree 100% with Tom---I am a licensed Structural Engineer and there are many factors that affect the design---such as support spacing, continuous or simple span, type of steel, actual live load and dead load, shear stresses, etc,etc

David G · Jan 3, 2017

That is worth spending the money to get licensed structural engineer to do calculations.

Remember you must cut out the floor and put in footings if you move the vertical supports.

David G · Jan 3, 2017

I have a referral for one if in Iowa.

BushogPapa · Jan 3, 2017

Sure you can "do it", but the support will have a not of give and "Bounce" in it..

I think you are going to end up deciding to keep one support in the span..

I have 3 or 4 24' x 12" beams from a culvert that might help you...nice and straight and not rusted..good condition..

I am in central, Ohio..

Neil Grant · Jan 3, 2017

I am a retired engineer. With the large span, it is not an easy fix as the beam will sag under its own weight. It is more of a defection problem as to what an acceptable sag is. As someone mentioned, you could predistort the beam like they arch tractor trailer flatbeds. I have a similar situation in my barn upper story with a 30 ft span. I live with the sag so I can get all the collector tractors in easy with a clear span.

Greg K · Jan 3, 2017

Not in iowa, but 25 miles west of the border by sioux city. Thanks for the input.

Greg K · Jan 3, 2017

Some more info, there are no load bearing walls on it that I know of. Stick built roof that resembles the truss concept, but I question it sometimes. I would like not to lose much more headroom while being able to open things up some. Looking at possibly finishing it in the future sometime. Thanks for all the advice so far.

rrc300 u · Jan 3, 2017

For what it's worth you might think about putting two beams evenly spaced from the sides as opposed to one down the center. I'm no engineer but I would bet you get away with a smaller beam and less poles holding it. My .02 lol.

Crazy Horse · Jan 3, 2017

I see your basement is unfinished, sounds like you are planning to finish it and thus the idea of removing the posts. OK, I can see that if you want a pool table, but if you are leaving things "as is" down there, why not live with the posts? Seems I remember something about if it ain't broke, don't fix it !!

Yukon3639 · Jan 3, 2017

(quoted from post at 08:33:50 01/03/17) Since I have no experience at all with calculating such a number I thought I would check here. In my basement there are three 2?10 nailed together to make a beam to support the floor joists. The span is 25' between the concrete walls. Currently there are 2 support poles to help it carry the span. If I were to replace the 2?10's with a steel I beam so that I could get rid of the posts, how big would it have to be? The house is a ranch style, built in 75, the kitchen is above the beam area. What other factors do I need to consider?
Never Never Never under estimate the load carried on your posts.
Consider the thought that the wood beam only carries the load between the posts.mthey are your connection to terra firma

Yukon3639 · Jan 3, 2017

(quoted from post at 08:33:50 01/03/17) Since I have no experience at all with calculating such a number I thought I would check here. In my basement there are three 2?10 nailed together to make a beam to support the floor joists. The span is 25' between the concrete walls. Currently there are 2 support poles to help it carry the span. If I were to replace the 2?10's with a steel I beam so that I could get rid of the posts, how big would it have to be? The house is a ranch style, built in 75, the kitchen is above the beam area. What other factors do I need to

Never under estimate the load carried by posts. The beam basically carries the load between the posts.
They are your only connection to terra firma

Joe W. · Jan 3, 2017

There may be reasons why you do not want to check with your local building inspector but when I had to change the support beam for a portion of my house roof, the local building inspector was very helpful by calculating the size of beam needed. First he told me to contact an engineer to determine the beam size but I must have moaned and groaned enough that he calculated the size for me. He calculated a 24' clear span glue lam beam that has been in place and hasn't moved in 25 years.

Greg K · Jan 3, 2017

Well there is something to what you're saying, however I feel that it is a poor layout with how it is set up now. Currently there are 2 finished bedrooms in the basement but everything else is unfinished. If I were to tear out the 3 walls that surround the floor drain in the middle and slide the furnace into the spot between the electrical panel then I can use the existing ductwork mostly. Then I move the water softener and water heater that are by the furnace and floor drain against the outside wall between the new furnace location and bedroom and use bifold closet doors for access. Then I replace the 2 wooden beams (in theory) with steel I beams so I can get rid of the 4 (2 each) posts. Now I have a large open area that I can build the way I want it (kitchenette area, TV area, pool table, bar, cut off end of a 57 chevy with the back seat to sit in, etc)

Greg K · Jan 3, 2017

There are no local inspectors for construction here. Electrical yes, but building and plumbing no. This is just in the thinking and planning stages right now, just wondering what I'm getting into. There are some local carpenter friends that I can ask too, but I wanted lots of opinions and viewpoints to hopefully come up with the best/most affordable alternatives.

Rob_Yesterday · Jan 3, 2017

Have the supply company calc it for you. Would you raise it into the floor to make a flush ceiling?

11-1/8 x 3-1/2 PSL or 9-5/8" x 3-1/2 glulam

Stephen Newell · Jan 3, 2017

That's too big of a question for a forum. You need a structural engineer there onsite to figure the load on that 25' span.

You will have to build temporary walls on both sides of the beam to take the wooden beam down. Then you are probably looking at lifting around 750lbs of beam to the ceiling. Have you determined you can get a 25' long beam into the basement where you need it?

Greg K · Jan 3, 2017

There is ductwork running through there so I can't make it flush.

Crazy Horse · Jan 4, 2017

I see what you mean, certainly a bit cut up and the post elimination would be a good start to get something better to work with. Good luck with your project, it'll be a bit of work for sure. That's a long span without support and the one comment about a steel beam sagging from its own weight is something to think about maybe. Lots of advice and suggestions, an engineer is likely the solution, especially if a guy had one living next door who drank beer with you ..... ha!

Greg K · Jan 4, 2017

Hey! Is this my engineer neighbor who likes beer? Just kidding. Even if I could get away with one post per span instead of 2, or moving the 2 so I can pick my open space. Like I said, just thinking out loud.

dpendzic · Jan 4, 2017

with that much of a span supporting the first floor I would not go without calculations that show the beam is ok to hold the load with allowable deflections---a normal floor joist should not deflect more than L/360--a ceiling beam not more than l/180

caterpillar guy · Jan 6, 2017

The sag in the middle as said will be your biggest factor. As you can get a beam to hold and with a small bridge to it with some strap iron it would be a minimal headroom loss to have it hold.
What if you had on post inline with the wall where the wall from the furnace is then rearranged the your rooms so that the post could be incorporated into the wall for the new rooms. Thus still supported with no loss of space, since the rooms could then be so it would have a longer narrower room for what you want.

Noah W · Jan 6, 2017

There is some good info HERE. You might find what you want in Module 7 even though it is for new construction.

Noah W

Beam span calculator

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