Beam Span?????

[carpenter383]

So are you saying that you want to modify the origional 12' 6" span and make it 17'?
Are there any load bearing walls/posts above this beam?
A steel I beam would be the best, but if that isn't possible then your gonna need to go wider than a 2x10 to span 17 ft. Over time it will sag for sure.
In my oppinion based on supporting only the floor, a 14" laminated beam would work fine.
You could add securely bolted angle braces at each end to shorten the span if possible.
If the beam also supports the 2nd floor or roof then you should talk to an engineer about it for sure.

 

[rtimgray]

Here's my take:

He wants to span 17'. The load being supported is a finished floor load from a residence. So the design load per square foot should be around 40 PSF/live and 10 PSF/dead for a total of 50 PSF.

This beam is supporting floor joists that are perpendicular to it. One side spans 11'-9", the other 12'-3". The beam will have to support the load over half the span of each side (the remainder of the load is supported by the concrete block walls on which the floor joists bear (or are attached).

So our total floor area to be supported is 12' wide (half of 11'9"+half of 12'3") by 17' long, for a total square footage of 204 sq. ft. Multiply this by 50 psf = 10,200 lb load.

What I'm not sure of it if there is additional loading to be supported, because I'm not sure if there is a wall above that is holding up weight and if there is ceiling and roof loading or if the trusses that he mentioned actually span the distance and while they may set on the wall that sets on the floor area, the floor actually bears (essentially) no additional load.

So now we've got to see if the existing beam will hold the weight.

The span table I have works in 2' increments, so I'll average between 16' and 18' span.

A 2x10 will hold up about 1,000 lbs over 17'. It's a triple 2x10, so that's only going to support about 3,000 lbs.

If it were supported at the mid-point of the span, then the loads are cut in half. A 2x10 at 8' span supports 2,139 lbs, so a triple would hold 6,417 lbs (which is well over half of our load of 10,200 lbs).

In the flow chart of this project, if he can add a post (and a footer), that will be the cheapest way to support this.

If a clear span is required, I would say he would need to go with an engineered beam or a steel beam.

From an old chart that I have, there are many beams that will support 10,200 lbs over 17 ft. The two lightest that I could find are a standard I-beam, 10 x 4 3/4 (25.4 lbs/ft) and a wide-flange I-beam (10 x 5 1/4, 21 lbs/ft). There are a couple of 8" tall beams that would support it as well. Both of the beams listed are rated to support at leat 16 kips at 18' span.

In my opinion, this is more of a carpentry equation than an engineering calcution. I think that we are dealing with (more a less) a residential situation, so dragging engineers into is probably not necessary.

Obvious disclaimer: unless local codes require stamped or engineer-approved plans, etc. etc. etc. I'm fortunate that I live in an area without such codes for residences, so I have never had to deal with building permits, inspections, etc. so I cannot account for that.

At any rate, bottom line, I don't think the existing beam is capaple of supporting the load, long term. I don't think that a good answer can be manufactured from dimensional lumber being attached to it. I think the options are either:

1. a post on the existing beam
2. a steel beam in place of or underneath the existing beam
3. a pre-engineered wood beam in place of or underneath the existing beam

Good luck and take care.

Edit:

Sorry, I didn't retain the part about the overall span being 34' and (I'm assuming) you want to separate it into two 17' spans instead of three 12'6" spans. In that case, I would use a steel beam under or in place of the existing and supporting it with a column (unless you wan't to add more posts).

And I see that an inspection is not required, so no worries there. I think it's obvious that the best thing to do is take the advice of unknown people from an internet forum! (This is what I hate about typing a post - I can can't convey voice inflection. I can't even find a proper emoticon. What I'm trying to do is come across with a good-natured ribbing comment, and I'm afraid it may sound like a condescending jack@$$. So I'm just trying to be funny, not a jerk....although sometimes, I can do both).

Anyway, good luck and take (again).

 

[LD1]

Here's my take:

He wants to span 17'. The load being supported is a finished floor load from a residence. So the design load per square foot should be around 40 PSF/live and 10 PSF/dead for a total of 50 PSF.

This beam is supporting floor joists that are perpendicular to it. One side spans 11'-9", the other 12'-3". The beam will have to support the load over half the span of each side (the remainder of the load is supported by the concrete block walls on which the floor joists bear (or are attached).

So our total floor area to be supported is 12' wide (half of 11'9"+half of 12'3") by 17' long, for a total square footage of 204 sq. ft. Multiply this by 50 psf = 10,200 lb load.

What I'm not sure of it if there is additional loading to be supported, because I'm not sure if there is a wall above that is holding up weight and if there is ceiling and roof loading or if the trusses that he mentioned actually span the distance and while they may set on the wall that sets on the floor area, the floor actually bears (essentially) no additional load.

So now we've got to see if the existing beam will hold the weight.

The span table I have works in 2' increments, so I'll average between 16' and 18' span.

A 2x10 will hold up about 1,000 lbs over 17'. It's a triple 2x10, so that's only going to support about 3,000 lbs.

If it were supported at the mid-point of the span, then the loads are cut in half. A 2x10 at 8' span supports 2,139 lbs, so a triple would hold 6,417 lbs (which is well over half of our load of 10,200 lbs).

In the flow chart of this project, if he can add a post (and a footer), that will be the cheapest way to support this.

If a clear span is required, I would say he would need to go with an engineered beam or a steel beam.

From an old chart that I have, there are many beams that will support 10,200 lbs over 17 ft. The two lightest that I could find are a standard I-beam, 10 x 4 3/4 (25.4 lbs/ft) and a wide-flange I-beam (10 x 5 1/4, 21 lbs/ft). There are a couple of 8" tall beams that would support it as well. Both of the beams listed are rated to support at leat 16 kips at 18' span.

In my opinion, this is more of a carpentry equation than an engineering calcution. I think that we are dealing with (more a less) a residential situation, so dragging engineers into is probably not necessary.

Obvious disclaimer: unless local codes require stamped or engineer-approved plans, etc. etc. etc. I'm fortunate that I live in an area without such codes for residences, so I have never had to deal with building permits, inspections, etc. so I cannot account for that.

At any rate, bottom line, I don't think the existing beam is capaple of supporting the load, long term. I don't think that a good answer can be manufactured from dimensional lumber being attached to it. I think the options are either:

1. a post on the existing beam
2. a steel beam in place of or underneath the existing beam
3. a pre-engineered wood beam in place of or underneath the existing beam

Good luck and take care.

Edit:

Sorry, I didn't retain the part about the overall span being 34' and (I'm assuming) you want to separate it into two 17' spans instead of three 12'6" spans. In that case, I would use a steel beam under or in place of the existing and supporting it with a column (unless you wan't to add more posts).

And I see that an inspection is not required, so no worries there. I think it's obvious that the best thing to do is take the advice of unknown people from an internet forum! (This is what I hate about typing a post - I can can't convey voice inflection. I can't even find a proper emoticon. What I'm trying to do is come across with a good-natured ribbing comment, and I'm afraid it may sound like a condescending jack@$$. So I'm just trying to be funny, not a jerk....although sometimes, I can do both).

Anyway, good luck and take (again).

IMO it is more than a simple carpentry equation. There is a lot of unknowns that neither you NOR I can account for without actually seeing it in person.

While your numbers are correct, they assume no loading from the walls and the supported roof trusses that he mentioned there are a total of 5. Depending on exactly how the stuss is designed and supported by other means will vary the amount of load that will be seen by the walls, and thus the floor and beam. There is no way to know for sure without a PE looking at it. And in your triple 2x10 beam you are also not accounting fot the 1/2" plywood.

I will also add that I have not seen a w10x21 beam. To my knowledge they jump from a w10x19 to a w10x22, but I could be wrong. Minor detail none the less.

And a question for the OP. Why are you wanting to go to all this trouble just to eliminate ONE post in the basement??? You mentioned it is already that the current beam is supported by 2 exixting posts @12'6" appart. And you are wanting to cut it down to just one. WHY??

A carrier beam under a hous has to support HUGE loads. Most common is a 30x50 foundation with a BIG w8x28 beam running the entire length. And even them are supported at ever 12'6".

 

[rtimgray]

IMO it is more than a simple carpentry equation. There is a lot of unknowns that neither you NOR I can account for without actually seeing it in person.

While your numbers are correct, they assume no loading from the walls and the supported roof trusses that he mentioned there are a total of 5. Depending on exactly how the stuss is designed and supported by other means will vary the amount of load that will be seen by the walls, and thus the floor and beam. There is no way to know for sure without a PE looking at it. And in your triple 2x10 beam you are also not accounting fot the 1/2" plywood.

I will also add that I have not seen a w10x21 beam. To my knowledge they jump from a w10x19 to a w10x22, but I could be wrong. Minor detail none the less.

And a question for the OP. Why are you wanting to go to all this trouble just to eliminate ONE post in the basement??? You mentioned it is already that the current beam is supported by 2 exixting posts @12'6" appart. And you are wanting to cut it down to just one. WHY??

A carrier beam under a hous has to support HUGE loads. Most common is a 30x50 foundation with a BIG w8x28 beam running the entire length. And even them are supported at ever 12'6".

In fairness to me, I mentioned that I was unsure of the additional loading, so I agree that that is an important factor. That is definately something that would have to be considered.

Because the triple 2x10 is only rated to support about 3,000 lbs, the effect of the plywood is negligible in this case (unless a sheet of plywood could support an additional 7,000 lbs over 17').

I haven't seen a w10x21 either, but it shows up on my chart. Obviously going a with a lighter weight beam capable of supporting the load will be a cheaper alternative.

And I agree that someone knowledgeable should look at the situation and see all the loads involved, but unless it is required by code (and it isn't), having a PE is an unnecessary expense. It is just a simple calculation of total load over a distance and finding the appropriate structural member to support it.

I don't know WHY he wants to change the span; I just know THAT he wants to change the span. So I tried to answer his question as best I could.

And who knows .... maybe a PE is looking at this problem right now....

 

[dieselscout80]

Here's my take:

He wants to span 17'. The load being supported is a finished floor load from a residence. So the design load per square foot should be around 40 PSF/live and 10 PSF/dead for a total of 50 PSF.

This beam is supporting floor joists that are perpendicular to it. One side spans 11'-9", the other 12'-3". The beam will have to support the load over half the span of each side (the remainder of the load is supported by the concrete block walls on which the floor joists bear (or are attached).

So our total floor area to be supported is 12' wide (half of 11'9"+half of 12'3") by 17' long, for a total square footage of 204 sq. ft. Multiply this by 50 psf = 10,200 lb load.

What I'm not sure of it if there is additional loading to be supported, because I'm not sure if there is a wall above that is holding up weight and if there is ceiling and roof loading or if the trusses that he mentioned actually span the distance and while they may set on the wall that sets on the floor area, the floor actually bears (essentially) no additional load.

So now we've got to see if the existing beam will hold the weight.

The span table I have works in 2' increments, so I'll average between 16' and 18' span.

A 2x10 will hold up about 1,000 lbs over 17'. It's a triple 2x10, so that's only going to support about 3,000 lbs.

If it were supported at the mid-point of the span, then the loads are cut in half. A 2x10 at 8' span supports 2,139 lbs, so a triple would hold 6,417 lbs (which is well over half of our load of 10,200 lbs).

In the flow chart of this project, if he can add a post (and a footer), that will be the cheapest way to support this.

If a clear span is required, I would say he would need to go with an engineered beam or a steel beam.

From an old chart that I have, there are many beams that will support 10,200 lbs over 17 ft. The two lightest that I could find are a standard I-beam, 10 x 4 3/4 (25.4 lbs/ft) and a wide-flange I-beam (10 x 5 1/4, 21 lbs/ft). There are a couple of 8" tall beams that would support it as well. Both of the beams listed are rated to support at leat 16 kips at 18' span.

In my opinion, this is more of a carpentry equation than an engineering calcution. I think that we are dealing with (more a less) a residential situation, so dragging engineers into is probably not necessary.

Obvious disclaimer: unless local codes require stamped or engineer-approved plans, etc. etc. etc. I'm fortunate that I live in an area without such codes for residences, so I have never had to deal with building permits, inspections, etc. so I cannot account for that.

At any rate, bottom line, I don't think the existing beam is capaple of supporting the load, long term. I don't think that a good answer can be manufactured from dimensional lumber being attached to it. I think the options are either:

1. a post on the existing beam
2. a steel beam in place of or underneath the existing beam
3. a pre-engineered wood beam in place of or underneath the existing beam

Good luck and take care.

Edit:

Sorry, I didn't retain the part about the overall span being 34' and (I'm assuming) you want to separate it into two 17' spans instead of three 12'6" spans. In that case, I would use a steel beam under or in place of the existing and supporting it with a column (unless you wan't to add more posts).

And I see that an inspection is not required, so no worries there. I think it's obvious that the best thing to do is take the advice of unknown people from an internet forum! (This is what I hate about typing a post - I can can't convey voice inflection. I can't even find a proper emoticon. What I'm trying to do is come across with a good-natured ribbing comment, and I'm afraid it may sound like a condescending jack@$$. So I'm just trying to be funny, not a jerk....although sometimes, I can do both).

Anyway, good luck and take (again).

Not two 17' spans the one span is 16', but it has a load bearing wall under it with one steel post at about 15' and multiple doubled 2"x4" and one tripled 2"x4".

Here are some pics and some drawings.

 

[dieselscout80]

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

I've never considered making the existing beam wider only deeper.

 

[oldnslo]

For reference Code here in northern Illinois allow 9' span with three 2x10's on a single story house.

 

[rtimgray]

Am I correct in assuming that (what you are calling) the truss supports run from the attic area and are either bearing on or are inside the hallway way, which in turn sets on the floor joints that are supported by the beam?

If that is the case, we just need to add together the area of the roof that is being supported by truss supports in the same manner in which we did the floor area being supported and add that to the calculation (and account for the dead weight of the wall).

Are the trusses (are they trusses or rafters - because I don't see any of the webbing that trusses have, so I'm wondering if they are not just rafters) running parrallel with the 34' dimension of the house? Is the peak of the roof in the middle (and I have no idea if it is a simple gable roof or if it is more complicated than that).

I would still say that it will boil down to that there is not a "good" way to do it by adding dimensional lumber to the existing beam. I think you will still have to either go with an engineered wood beam or a steel beam (or add/leave a post).

Good luck.

 

[dieselscout80]

I just taked to a building supply place and they recommended removing the old beam for the 17' span and replacing it with 2 LVL's either 14" or 16" deep. LVL's are 1.75" thick so I'll have to put a 2"x10" or a 2"x12" between them to equal my current beam width.

 

[dieselscout80]

Am I correct in assuming that (what you are calling) the truss supports run from the attic area and are either bearing on or are inside the hallway way, which in turn sets on the floor joints that are supported by the beam?

If that is the case, we just need to add together the area of the roof that is being supported by truss supports in the same manner in which we did the floor area being supported and add that to the calculation (and account for the dead weight of the wall).

Are the trusses (are they trusses or rafters - because I don't see any of the webbing that trusses have, so I'm wondering if they are not just rafters) running parrallel with the 34' dimension of the house? Is the peak of the roof in the middle (and I have no idea if it is a simple gable roof or if it is more complicated than that).

I would still say that it will boil down to that there is not a "good" way to do it by adding dimensional lumber to the existing beam. I think you will still have to either go with an engineered wood beam or a steel beam (or add/leave a post).

Good luck.

You are correct they are rafters.