Beam Span?????

[dieselscout80]

I want to know how far a beam can span. I finishing my basement.

Beam in questions is made of three 2"x10" and a 1/2' sheet of plywood nailed together.

It is part of the main floor of my house and has floor 2"x10" joists attached perpendicular on both sides on 16" centers. The joists are supported by the block foundation on both sides one side spans about 11'9" the 12'3". The load above the beam is a hallway and a bed room/office and in the attic there are 5 roof truss supports.

I want to span 17' if possible without additional supports.

First question can the existing beam support the 17' foot span?

Second what do I need to do to reinforce the existing beam?

I've thought about running another beam under it made from 20' either 2"x6", 2"x8" or 2"x10" with 1/2" plywood and attach it to the existing beam with metal plates between the joists.

I've thought about running another beam under it made from 20' either 2"x4", 2"x6" steel and attach it to the existing beams.

A friend who is a ENG mentioned cutting the plywood out and taking a I beam with a 7" web and having the the top flange removed and placing it where the plywood was and then bolting through the 2"x10". How would I cut the plywood out my only idea has been a chainsaw?

Could I use 3 x 2 x 3/16 Steel Angle on both sides of the existing beam and bolt it through and do the same thing?

 

[bp fick]

Your local building department can tell you what they will approve.

Clear spanning 17' is a looooong way for a carrier bean, if I understand you correctly. This center beam carries the floor joists?

 

[LD1]

Your local building department can tell you what they will approve.

Clear spanning 17' is a looooong way for a carrier bean, if I understand you correctly. This center beam carries the floor joists?

Agreed. There are specific codes and requirements that vary by area/district/location, whatever. For a residential structure, I would advise you to get whatever you have in mind approved by whoever the appropriat authority is in your area.

And when it comes to basic strength, you gain MUCH more by going deeper rather than wider. And you really need to know the loading that is going to be on the beams, and not just " a hallway and the floor joists". Calculating the span gets a lot more complicated with wood/plywood laminated beams, certain types of connections, how they are attached, hast size nails, type of glue, ETC. It is not as cut and driedas just sizing a steel beam for load x.

Get with a PE in your area and do it to code, follow his reccomendations. It will be well worth the money and peice of mind.

 

[dieselscout80]

Your local building department can tell you what they will approve.

Clear spanning 17' is a looooong way for a carrier bean, if I understand you correctly. This center beam carries the floor joists?

Not sure what you mean by carrier beam, but the joist are butted into the beam. I plan to add metal joist backets that will support the joist and be screwed to the beam.

 

[bp fick]

Not sure what you mean by carrier beam, but the joist are butted into the beam. I plan to add metal joist backets that will support the joist and be screwed to the beam.

Yup. In our lingo, that's a carrier beam. It will be carrying something akin to 28 floor joists and all they weight that they support in walls, flooring, furniture, etc. Agreed you need to consult with an engineer and have approval by the township/village/city/county etc. You are not asking the impossible. Not at all. It's just that "guessing" is reckless. You need scientific facts. Best wishes. Around here, we use 8" i beam steel. But, we post it every 12 ft. You're asking to clear span 17 feet.

 

[ss4010]

I want to know how far a beam can span. I finishing my basement.

Beam in questions is made of three 2"x10" and a 1/2' sheet of plywood nailed together.

It is part of the main floor of my house and has floor 2"x10" joists attached perpendicular on both sides on 16" centers. The joists are supported by the block foundation on both sides one side spans about 11'9" the 12'3". The load above the beam is a hallway and a bed room/office and in the attic there are 5 roof truss supports.

I want to span 17' if possible without additional supports.

First question can the existing beam support the 17' foot span?

Second what do I need to do to reinforce the existing beam?

I've thought about running another beam under it made from 20' either 2"x6", 2"x8" or 2"x10" with 1/2" plywood and attach it to the existing beam with metal plates between the joists.

I've thought about running another beam under it made from 20' either 2"x4", 2"x6" steel and attach it to the existing beams.

A friend who is a ENG mentioned cutting the plywood out and taking a I beam with a 7" web and having the the top flange removed and placing it where the plywood was and then bolting through the 2"x10". How would I cut the plywood out my only idea has been a chainsaw?

Could I use 3 x 2 x 3/16 Steel Angle on both sides of the existing beam and bolt it through and do the same thing?

What your friend was talking about is called a flitch plate beam. Below is a link to a worked example with at 2x10 beam / flitch plate with 1/2" steel.

STRUCTUREmag: Flitch Plate Beams


The example shows a 12' span.... Seems to me in your case it would make economic sense to break it up into two 8.5' sections. Which is probably what you already have...

Steve

 

[dieselscout80]

What your friend was talking about is called a flitch plate beam. Below is a link to a worked example with at 2x10 beam / flitch plate with 1/2" steel.

STRUCTUREmag: Flitch Plate Beams


The example shows a 12' span.... Seems to me in your case it would make economic sense to break it up into two 8.5' sections. Which is probably what you already have...

Steve

The existing beam had two support posts 12' 6" apart in the 34' total span.

We don't having an inspector/inspection program out here.

 

[nickel plate]

Go to your local lumber yard that has experience with engineered beams, not glu-lams but beam products that are manufactured from veneers or strands, Georgia Pacific, Louisianna Pacific, whoever services your area of the country. A good over the counter lumber salesman can easily through the manfacturer's tech tables tell you what size manufactured beam you need for your loading and span requirements. Use the L/480 tables or higher. Please don't take this on your own by sandwiching whatever together as life and limb are at stake.

 

[CurlyDave]

The existing beam had two support posts 12' 6" apart in the 34' total span.

It is a whole lot easier to span 12'6" than 17'.

You really need to have this beam designed by an engineer.

The steel angle idea is not going to work.

The right way to get rid of the plywood is to start over with new 2x10s.

You can probably buy an engineered wood beam which will span the length required, but the depth will be a lot greater than 9.5". Whether you can accept the reduced headroom in that part of the basement is up to you.

A steel beam can probably span this distance, but costs are higher than wood.

The other way to go would be to design the basement with more posts. I haven't done any calculations, but my sense of this is that if you could work out a floor plan with three posts, four nearly even spans, you could use a wooden beam with a depth you can live with.

I doubt the original beam met modern standards...

As has been mentioned, you get a lot more good from a deeper beam than you do from a wider one.

 

[nickel plate]

It sounds like the basement floor and surround is already in but I am unclear of that. If it is and you decide to add posts to shorten the spans, at that point you don't have any bearing post footings in place which would mean cutting the slab and digging footings and adding steel for each post. That in itself would be monumental. Start by calcing (shouldn't cost you a dime) an engineered beam.