Beam size?

[nathank]

Hello all!

Quick question for the professionals....

I am going to add a loft above my workbench for additional storage. In the picture you can see it will be flush with the top of the bathroom and span the entire length of that wall. It will be the same depth/height of the bathroom. I'll hang lights under for bench lights.

My question is, how large of a beam would I need to span that 18ft run? I would really like to stay away from having posts in front of the bench if at all possible. I'll use 2x6s for the joists.

Bear in mind, this is for storage. There will be roughly 20-24" of space up there, so we're not talking about storing anything large. It will be storage for table saw, miter saw, etc. I also would like everything to stay put and not fall on my head!

 

[Junkman]

Size of items stored isn't the question, but the weight of the items stored above. If it were mine, I would consider using a lam beam and depending on the weight of the stored items, possibly even using two of them fastened together. Also, you can increase the weight carrying capacity by having the 2" x 6" joists spaced at 12" on center. You also need to calculate the weight of the floor into this equation. One thing that I would do is to have a slight rake to the floor tilted toward the outside wall to keep anything that might be stored up there from rolling forward, possibly hitting you on the head when you are working below.

 

[nathank]

Let's pretend I have no idea what a "lam beam" is. Is that something I can get at Lowes or HD?

What would be a good alternative?

 

[PAToyota]

Let's pretend I have no idea what a "lam beam" is.

Laminated beam. Lowes Engineered Lumber

 

[ddawg16]

Using building codes/guidlines for live loads, a single 2x12 will be fine for the span...by single, I mean one in front....you will also need one in the rear. Then use the 2x6's as your floor joists in between the 2x12's.

I would suggest using 4x4 posts bolted to the 2x12's.

If you expect to put anything else heavier than what you noted, then consider adding more 2x12's. Per code for that span, you should have a 2x12 on 12" centers....so, if the area is 6' deep, that would be 7 2x12's.

 

[kbs2244]

How far is that roof support from wher you want the edge of the shelf?
You could just use some threded rod as hangers to support a 2x6 beam and the the sheet metal joist hangers to support 2x6's back to the wall.

 

[tundradude]

Let's pretend I have no idea what a "lam beam" is. Is that something I can get at Lowes or HD?

What would be a good alternative?

Also referred as LVL or Laminated Veener Lumber

 

[nathank]

What if I used (2) 2x10s or (2) 2x12s like this

 

[buening]

How deep is this space? With only 2' of area from the top of the platform to the ceiling, you won't have to worry about live loads (walking up there)

 

[Old61]

You can do it without the spacers. The spacers are there for wood framed openings.

 

[IHI]

Personally, i would just grab 2- 9"x18' LVL's, nail them together with some 16d's every 16" o.c. so you can get a wide open space across the front where you will be loading storage items onto the shelf. Across the back, a simple 2x4 lagged into the wall studs if they're 16" o.c. with standard GRK 3 1/2"x 5/16" structural screws and your good to go. Relatively cheap with no worries about future sag across the front on the 18' span.

 

[buening]

Personally, i would just grab 2- 9"x18' LVL's, nail them together with some 16d's every 16" o.c. so you can get a wide open space across the front where you will be loading storage items onto the shelf. Across the back, a simple 2x4 lagged into the wall studs if they're 16" o.c. with standard GRK 3 1/2"x 5/16" structural screws and your good to go. Relatively cheap with no worries about future sag across the front on the 18' span.

It is a steel framed building according to his picture, so there are no studs. If his loading was fairly light he could tie into existing columns but I would feel more comfortable if he built his own columns to support the shelf.

 

[IHI]

Easy:

2 sets of beams- 1 across the back and 1 across the front, both will sit on the bathroom wall pictured for that support.

on the wall out of sight he'll have to install some jacks and header and then the other end of the beams for shelving can rest on that...nice free spanning shelf system.

little pricey and labor involved, but that's just the nature of pole buildings and working in pre-existing spaces, but this is'nt rocket science by any means, primative at best.

 

[nathank]

The top of the loft will actually line up with the top of that bathroom.

No worries on the back support. I framed a wall that all the peg is fastened to, the back support is covered... I just need to know on the front beam size for that 18' span. I will use a 4x4 post at each end to support the front beam.

So technically a single 2x12 can span 18' if we're not worried about live loads? Can two 2x10s span 18' if I nail them together?

We're not talking about having a party up there, I just need a place to throw some icechests and a miter saw.

 

[buening]

How deep is the space? I know of the 18' span, but is the depth 8', 6', 3'?? This will determine if you can get away with a front and rear beam, or if you need intermediate beams.

 

[nathank]

How deep is the space? I know of the 18' span, but is the depth 8', 6', 3'?? This will determine if you can get away with a front and rear beam, or if you need intermediate beams.

6ft on the depth

 

[buening]

Two 2x10 bolted together should be sufficient for the front beam as long as you aren't storing mass steel or anything dense covering the entire area. For heavier stuff, try to keep them away from the middle of the span. If the back wall is framed, you should be able to get by with a single 2x10 at the back since it is really a supported span. LVL's will not sag as much over time, but they will add more expense to the project. I would suggest at a minimum that the 2x10 beams be #2 with a #1 grade preferable. This all assumes that your back wall and your bathroom wall can handle the loads, which have not been checked. I didn't check the columns either, but the 4x4 should be sufficient as long as they are only used to support the shelf above. I assumed a 25psf loading on the entire area and used Southern Pine bending stress properties for No 2 non-dense.

This is not a professional design and therefore no liability shall be placed on me.

 

[sberry]

There may be a clearer pic if someone knows where to find it, I think someone on Shopfloortalk had it.

 

[buening]

That second pic can be found in the AISC Steel manual, although the tables from that manual cover all kinds of steel shapes. They also have allowable distributed loads, along with the allowable point loads.

The first one uses 100psf Live Load. According to the IBC, a residential dwelling shall be designed for 20psf Live Load for attics that are uninhabited. I added 5psf for the dead load of the wood. I believe there are some tables from the NDS or AWC website for wood beams, but I think they are restricted to Engineered Wood.

Here is a nice calculator from AWC, but doesn't really work in this case.

 

[buening]

sberry, I found the location for your first pic. See here: http://www.awc.org/Standards/wsdd.html

For example from that link, see the tables for span 18' http://www.awc.org/pdf/WSDD/C2D.pdf

For No. 2 Non-Dense, the Fb=1350 for southern pine according to the latest NBS code. I feel more comfortable with 1100 for a little factor of safety. From that table for 18' span, the total allowable weight per foot (w) is 48 lb/ft for a single 2x10. Using two 2x10's you are allowed 96 lb/ft. Using a 25psf for a 3' distributed width (front beam takes 3' of loaded area, back beam takes the other 3'), you have 75 lb/ft which is less than 96.



But, keep in mind that those links and data is out of date since it includes 1992 revisions. The checks I performed are using the 2005 NDS and the numbers are a bit different. I wish they had handy tables like that in the NDS.

 

[nathank]

I really appreciate all the help guys. I think I am going to go with the (2) 2x10s.