1/4 - 20 Threaded Rod For 55Lb Light

Ravenvalor

Senior Member
Hello,

I have to mount a 55Lb light with angle bracket (total weight) onto an 18" thick brick wall outside. The wall rises above the roof line about 2' so the light will be at the highest point of the wall which will be above the roof line. The footprint of the angle bracket is 5" X 5" so I was thinking about installing 4 - 1/4-20 rods through the wall and attaching to kindorf on the back of the wall and the angle bracket to the rods on the front of the wall. The length of the angle bracket pipe is 8" so the light will be above the wall. Would someone please advise me whether or not the 4 - 1/4-20 threaded rods will sufficiently hold the bracket with light? This job is in central NC so it can get windy here. The wall may be 75 years old so the moisture content is probably high. Should I use stainless steel threaded rod? Is it weaker than regular threaded rod?

Thanks for the help.
 

kwired

Electron manager
Hello,

I have to mount a 55Lb light with angle bracket (total weight) onto an 18" thick brick wall outside. The wall rises above the roof line about 2' so the light will be at the highest point of the wall which will be above the roof line. The footprint of the angle bracket is 5" X 5" so I was thinking about installing 4 - 1/4-20 rods through the wall and attaching to kindorf on the back of the wall and the angle bracket to the rods on the front of the wall. The length of the angle bracket pipe is 8" so the light will be above the wall. Would someone please advise me whether or not the 4 - 1/4-20 threaded rods will sufficiently hold the bracket with light? This job is in central NC so it can get windy here. The wall may be 75 years old so the moisture content is probably high. Should I use stainless steel threaded rod? Is it weaker than regular threaded rod?

Thanks for the help.
I don't know the rating of 1/4" rod, but seen it holding much more than 55 pounds many times.
 

MAC702

Senior Member
Even if the tensile strength of stainless was less than galvanized, it would still be plenty sufficient for your job. The rods won't be the weak point.

As for stainless, when I was in Florida, everyone used stainless for everything, even staples.
 
This sounds like a good install, though I'd probably use 5/16 or 3/8 rod personally. If you cinch it down tight then the load mainly transfers to the wall thru friction between the bracket and brick. The main thing is to get it tight and ensure it stays that way. I would use stainless rod and stainless or polymer coated nylon nuts with appropriate SS washers. Stainless rod is a bit weaker but it won't matter here. However, don't use an impact tool to install SS nuts onto SS fasteners as they like to gall and seize very quickly. Hand tightening won't do that. The polymer coated nuts are designed not to gall.

I'd make the front bracket, then drill the holes thru, then make the back bracket fit on site. You are unlikely to be able to drill thru 18" of wall perfectly parallel. May need to cram some duct seal or silicone in the holes if they blow out much, in order to keep water out of the wall.
 

PaulMmn

Senior Member
Be careful of the brickwork! Sometimes the old mortar (or the bricks) isn't as strong as you think it is!
 

al hildenbrand

Senior Member
The wall may be 75 years old so the moisture content is probably high.
In my experience, you'll learn the most about the carrying capacity of the masonry itself by whether you can drill through it without blowing the bricks out. If the wall cap flashing has not been maintained over the 75 years, and enough freeze/thaw cycles have occurred, that masonry can get pretty soft.
 

hbiss

EC, Westchester, New York NEC: 2014
Hello,

The footprint of the angle bracket is 5" X 5" so I was thinking about installing 4 - 1/4-20 rods through the wall and attaching to kindorf on the back of the wall and the angle bracket to the rods on the front of the wall. The length of the angle bracket pipe is 8" so the light will be above the wall. Would someone please advise me whether or not the 4 - 1/4-20 threaded rods will sufficiently hold the bracket with light? This job is in central NC so it can get windy here. The wall may be 75 years old so the moisture content is probably high. Should I use stainless steel threaded rod? Is it weaker than regular threaded rod.
I've done similar with a fabricated mast to support aerial cable between buildings probably 20 years ago. This was a lot heaver than 55 pounds and then there was considerable tension also. It looked like an upside down Easter Seals logo, 8 feet of 4" square tubing with two pieces of 4x4 angle iron welded to the bottom maybe two feet apart. Holes were drilled to accept 5/8" pole line bolts. I also made up big square plates for the other side with holes drilled in them to act like washers for the bolts and nuts to distribute the load over a larger area of brick. This was a 75 year old building also and as far as I know that mast is still there today. I actually sent it out to be hot dip galvanized after it was fabricated.

So my recommendation would be 3/8 threaded rod, stainless is a good idea. Then make a plate for the back side (instead of the Kindorf) with four holes for the threaded rod and nuts. Make it maybe 12x12" out of 1/4" thick steel.

So if that thing is going to come down it's going to have to take a 12x12" piece of the wall with it.:cool:

-Hal
 

Ravenvalor

Senior Member
These are great suggestions.
Thanks....
I think I will try to find 5/16 stainless threaded rod because I have a 3/8" x 30" masonry bit. I will also use polymer coated nuts and put silicone in the holes to keep moisture out. Making a nice big 12 x 12 back plate is a great idea. I will make one of those also. Last but not least, if the brick drills like butter I may have to lower the light enough so the threaded rods go into the building as opposed to above the roof line. It should be stronger brick there....
Once again thanks for the great advice....
 

Ravenvalor

Senior Member
The customer also wants me to mount the same type light onto the end of a ceiling rafter that juts out of a building but is protected by the roof. If I drive 4 - 1/2" x 8" lag bolts into the wood will it hold this light? I tested another similar rafter with a 1/2 x 6 lag bolt and the wood was in good shape.

Best regards....
 

MAC702

Senior Member
... If I drive 4 - 1/2" x 8" lag bolts into the wood will it hold this light? ...
Seems way overkill to me. I hang gates on smaller hardware. Use the proper pilot drill so you can drive the lags without stressing them and snapping off the heads. I'd probably hang it with 5/16" x 3" lags. Maybe even 1/4" without worry if it's all I had on the truck at the time.
 

Ravenvalor

Senior Member
Seems way overkill to me. I hang gates on smaller hardware. Use the proper pilot drill so you can drive the lags without stressing them and snapping off the heads. I'd probably hang it with 5/16" x 3" lags. Maybe even 1/4" without worry if it's all I had on the truck at the time.
Thanks for the help MAC,

My concern is that the angle bracket that I am attaching to the rafter is 14" long so it rises up above the roof line. We sometimes get hurricane force winds here in central NC. Actually I would like to raise the light up another 5'. If you are not concerned about the wind, would you recommend adding an extension to this angle bracket in order to raise the light up even more?

Best regards,
 

synchro

Senior Member
The customer also wants me to mount the same type light onto the end of a ceiling rafter that juts out of a building but is protected by the roof. If I drive 4 - 1/2" x 8" lag bolts into the wood will it hold this light? I tested another similar rafter with a 1/2 x 6 lag bolt and the wood was in good shape.

Best regards....
I'm not sure what the exact configuration you have is, but avoid putting lag bolts into the end grain of the rafter it at all possible. Doing that tends to split the wood and has lower pull-out force values.
 

Ravenvalor

Senior Member
I'm not sure what the exact configuration you have is, but avoid putting lag bolts into the end grain of the rafter it at all possible. Doing that tends to split the wood and has lower pull-out force values.
I could not agree with you more synchro. I was hoping that the length of a 1/2" x 6" lag bolt would make up for that lower force value. The tensile strength of the bolt is about 3,000Lbs and the sheer strength is about 2,000Lbs. Of course that will not mean anything if the wood will not hold it. I could also add a support arm to the light which would help stabilize it.
 
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