# Maximum stuff I can screw into wood beam.



## Sleeper (Mar 24, 2009)

I have two 8”x16” beams supported by one 8”x8” post in the middle covered in 5/8” gypsum board and I’ve been hanging everything off of them. I have ladders, clamps, tool, and electrical conduit screwed to them. I want to hang more stuff, but I’m getting concerned about how much is enough because there is a lot of weight above with 4 bedrooms and a clay tile roof. 

I know the roof is really heavy and I once worked on a job where new footings & columns had to be installed to support a new tile roof. The house was about 30 yrs old and was designed for Composition roofing, but when the owner decided to replace it with Tile, the building inspection required a engineering report. 

I have predrilled every screw that I put into it so I would not have any splitting, but the original carpenters were animals and from the few walls that I have looked into, I found an Abomination of woodworking. 

Any Engineers here or anybody who has had experience with wood beams? My house is 20 years old and should have been built with at least some consideration to earthquake construction.

Oh the builder has had a few class action law suits against them so I can’t trust that the house is that well built


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## Dave Paine (May 30, 2012)

A good number of sites with the formula to calculate bending stress on a beam. One example with various scenarios.

http://engineersedge.com/beam-deflection-menu.htm

You will need to measure the unsupported distance. Very important for a beam.

You will also have to estimate the modulus of elasticity, which may be searched assuming you know the wood species.

All beams have some deflection. The unknown is how much deflection is allowed by your local code.

Wood can deflect a LOT before it will break. I have seen folks walking on planks which deflected several inches. Looked scary, but then they bounced back.


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## Sleeper (Mar 24, 2009)

Thanks Dave, I think that pretty much has been determined by the building department when they issued the permit. 

What I‘m looking for is how many holes and screws can I drive into the surface of the wood before it is weakened. I’m also pretty sure it can support the weight, but I would think too many holes would be just as bad as termite damage. I have seen 2x4 studs in walls being removed that had so many holes that they just busted up into splinters when hit with a sledge while others without holes held up pretty good.

I know as an electrician that I cannot drill within the middle third of a floor joist SPAN (not the width, height, or thickness) and there were other considerations for beams which I just avoided altogether. I had one job where the architect specifically requested on the plans that NO holes could be drilled through the beams.


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## cabinetman (Jul 5, 2007)

Here's a few thoughts. Depending on where you positioned the screws, lets say it's on the side of the beam. You could add some thick stock of solid wood, or doubled up ¾" plywood to the beam, like sistering. If the add on is at the bottom, the weight will be more dispersed than just screwing into the beam.








 







.


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## woodnthings (Jan 24, 2009)

*here's a few more thoughts*

I don't think it's an issue of weight..JMO. Your question is how many holes will weaken the beam. When you use a screw and a pilot hole, the missing wood fibers are only the amount of the pilot drill. The screw then fills up the hole, but does not "reconnect" the fibers. Where the beam is in compression, the filled holes don't matter. Where the beam is in tension is where it matters. 
For illustration:
Take a 1" x 6" piece of styrofoam and support it on both ends, narrow edge up. Press down in the center and watch what happens. It will be in tension on the bottom edge and compression on the top edge. Somewhere in the center there will be minimal forces. If you continue to press down it will come apart first on the bottom. It may not even separate at the top because that area was being compressed. 

A 8" X 16" beam will take a lot of holes before it's weakened much...JMO. If you only drill into it 2" for a screw, you still have another 6" remaining. I would use 3/8" lag screws at most...JMO. A 1/4" lag screw will hold a lot of weight, and it will probably start to bend before it breaks off if you overload it giving you a warning. 
Household stuff like ladders and clamps, while heavy to lift, in relation to a huge beam are not all that much. 

I would be concerned that a solid wood beam is structurally sound, with no rot, splits or cracks and even those don't seem to matter in barns and other structure I've seen. Also if the beams are laminated, unlikely but way better if they are. 

You can make an "over the top" hanger that rests on the top surface of the beam if it's accessible. This would eliminate the need for large screws and could be used on both sides, like a top hat shape. 










I don't see the need for the gypsum facing and I would remove it, personally. 

How about a photo of what you have?


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## Sleeper (Mar 24, 2009)

I can’t go over the top because the ceiling and beams are covered with gypsum board for fire safety. The 5/8” gypsum board is required by building code and I would have to replace it in order to sell my house. Plus I was told that the insurance would be void if there was a fire and I removed it.

I’m thinking about Cabinetmans idea of the plywood and I’m now definitely going to wrap the post with plywood all the way down to the floor so nothing is actually supported by the post.

I don’t know about the beams because they are 20 ft long. I not only have a lot of stuff to put on the post, but I want to hang some stuff over my assembly table like an air hose, some clamps and maybe a pull down shelf for glue and stuff.


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## Alchymist (Jan 2, 2011)

Sleeper said:


> Thanks Dave, I think that pretty much has been determined by the building department when they issued the permit.
> 
> What I‘m looking for is how many holes and screws can I drive into the surface of the wood before it is weakened. I’m also pretty sure it can support the weight, but I would think too many holes would be just as bad as termite damage. I have seen 2x4 studs in walls being removed that had so many holes that they just busted up into splinters when hit with a sledge while others without holes held up pretty good.
> 
> I know as an electrician that I cannot drill with the middle third of a floor joist and there were other considerations for beams which I just avoided altogether. I had one job where the architect specifically requested on the plans that NO holes could be drilled through the beams.


I *THINK* you have that backwards - any holes *should* be in the middle of the joist, the area under least stress. If I'm wrong, someone will be sure to correct me! :yes:


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## Sleeper (Mar 24, 2009)

Alchymist said:


> I *THINK* you have that backwards - any holes *should* be in the middle of the joist, the area under least stress. If I'm wrong, someone will be sure to correct me! :yes:


I'm talking about the span. If the span is 18 ft you can only drill in the first 6 ft of each side and yes your interpretation would be true for the width of the board which is not the case here.

Sorry to confuse you, but it just blows my mind how specific you have to be here. It just never dawned on me that anybody would think anything else.


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