DIY Ceiling mounted shelf?


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Old 03-03-21, 03:21 PM
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DIY Ceiling mounted shelf?

Hey

due to the circumstances, I'd like to have a DIY shelf that can be mounted to the ceiling. I found one interesting suggestion that basically goes like this:

1.: put heavy-duty anchor-bolts into the ceiling
2.: screw threaded rods into the bolts
3.: screw nuts onto the rods to carry the boards

I like the simplicity of this build but I'm concerned about the nuts carrying the weight. Any thoughts or ideas are highly appreciated!

p.s.: the shelfs should be ca. 6-6'5 long and able to carry 200-250 lbs combined.
 
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Old 03-03-21, 03:39 PM
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250#'s distributed across four anchor points is only 60#'s each, easily within the capacity of a threaded bolt into a solid roof truss/floor joist.

So why not attached to a wall, a lot less work!
 
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Old 03-03-21, 03:59 PM
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Use fender washers above your nuts, should be fine. I would hope if its 6 feet long you will be hanging it from at least 6 points.
 
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Old 03-04-21, 05:01 AM
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Key point:

threaded bolt into a solid roof truss/floor joist.


 
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Old 03-04-21, 05:06 AM
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You can not drill into the top or bottom of a truss. Drilling a hole for anchor bolts or threaded rod removes part of the wood making the truss weaker. So, if your house is framed with engineered trusses then you cannot hang shelves like you mentioned. If your ceiling/roof is stick built it might be an option.
 
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Old 03-04-21, 05:11 AM
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That's true. If its really a truss, you would be better off nailing 2x4s across the ceiling and put your furniture lags/couplers into that. And even if you dont have trusses, and just have joists, it will be better to nail up 2x4s first. The problem is the size of the hole, and we don't know what size rod you are going to use.

Thing is, the op didn't say "truss". But its a good question.
 
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Old 03-04-21, 05:19 AM
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Well, I jumped to the conclusion he was talking about ceiling/wall anchors and went "Ooooooooh!". And my next thought was what you said, attach boards to the joists and go from there.
 
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Old 03-04-21, 08:46 AM
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Here we go again, getting into the finite micro details of a code.

Every manufacturer is different, every installation is different, but you can drill into the bottom chord. Horizontal or vertical, that I have never had the pleasure to research.



There are tons of questions on this form about people mounting storage racks, bike hoists, even garage door opener and many, if not all of them are going right into their roof trusses.

Here is a link for a garage storage rack, 600# capacity, guess where the lag bolts are going.

https://www.fleximounts.com/wp-conte...48S-Manual.pdf

So is the position for this forum that nothing ever gets attached to the ceiling or do we use a bit of common sense based on the application? Ive yet to ever see any roof/truss system built that was so marginal that something of this nature would ever cause it to fail.
 
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Old 03-04-21, 09:13 AM
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In my area and the two truss manufacturers I work with do not allow to be drilled in any trusses in any location without engineering approval. The Inspections Dept. also follows this guidance and will fail the inspection if they find undocumented/unapproved holes. They allow nails and screws because they split (not cut) the wood fibers preserving the wood's strength. Holes remove wood, cutting the fibers and reduce the strength of the member. Whenever needing to drill into a truss I need to specify the location of the hole, it's orientation, size and why the hole is needed in the first place.
 
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Old 03-04-21, 12:59 PM
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is the position for this forum that nothing ever gets attached to the ceiling
The position of the forum is that members will not be allowed to contradict clear building codes or make alterations that should have the mfg's approval since following erroneous advice may endanger public safety.

Nails and drywall screws put holes in truss chords. Lags can make holes in truss chords. However those are of limited size and depth. Electricians should not bore in them.... Just like you don't bore holes in a header or beam. Trusslok fasteners are permitted at exterior wall top plates. But drilling clear through so as to bolt a threaded rod is not. Same reason an electrician shouldn't do that.

But the minute you say it's okay to drill vertically through a truss chord you go against the truss mfg's design limits. So for example, some bonehead is going to read that and think it's okay to drill a 5/8" hole to put a 1/2" threaded rod in which will barely leave 7/16 of wood on either side.

The safe advice is to simply fasten 2x4s to the ceiling and hang things on that. Pilot Dane aptly answered the rest.
 
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Old 03-05-21, 05:59 AM
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Is there a code requirement for a specific minimum amount of overbuild for structural components? For example, if the structural engineer knows the size or strength needed for each component of a truss do they add say 20% into their calculations as a safety factor? This could be for variances in lumber or component strength, construction irregularities, or future unforeseen modifications. Obviously they cannot anticipate everything that might occur over the life of the structure. But surely they know some types of structures are likely to be modified over their life.

No, that does not mean to just assume the item is overbuilt and will handle whatever the modification. Just wondering how much extra is built in by both the original engineer and the code officials. Just how close to absolute minimums are homes built? I understand overbuilding is costly. But surely there is some minimum amount of overbuild.

Guess that is one reason buildings sometimes fail during storms. Makes me wonder just how close to that edge we are.
 
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Old 03-06-21, 08:54 AM
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There is a certain amount of "overbuild" in almost everything. Soda bottles are stronger than they need to be to contain the liquid. Airplanes have extra strength/safety margins to account for accidents or freak weather encounters. And your house is also designed to handle higher than expected loads without failing. Your question isn't that simple though. On top of safety margins there are other criteria like flex. For example a truss floor system may be considered structurally sound, safe and have safety margin but could bounce an unacceptable amount when people walk on the floor. So, often structures are overbuilt even further for human reasons like making floor not bounce and "feel" sturdy under foot.

I don't have them at home with me now but I have the engineering sheets for the engineered products in my house. If I remember next week I'll look and see if they called out the safety margin they included.

----
For aircraft 1.5 (or 50% extra) is a common "overbuild". For example the Extra 300 I learned aerobatics in has a limit of 10 positive G's with one person. The aircraft can experience 10 positive G's without damage. To be certified it must demonstrate an ultimate limit of 15 positive G's which is often the failure point (when it breaks and your glad your wearing a parachute).
 
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Old 03-14-21, 09:12 AM
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Makes me wonder how often there are structural failures resulting from homeowner improvements? People who remove bearing walls, overload an attic floor, add windows to exterior walls without realizing loads above, etc.

I have done lots of structural changes over the years without permits. Always researched prior so I wasn’t doing something wrong. But, who knows, maybe I didn’t realize...
 
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Old 03-14-21, 09:43 AM
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I see it occasionally in real life. Usually it's plumbers or HVAC installers cutting or removing something that's in their way. A few weeks ago someone started a thread because one of their truss member failed, snapped right in half. It appeared HVAC contractors removed some members to make room for an AC in the attic causing one of the remaining pieces to break.

Many assume that they can do whatever counting on the safety margin to protect them. What they don't realize is that trusses are engineered to only have wood where it's needed. The top chord of a roof truss is designed to carry normal loads and has extra margin for that freak, heavy snowstorm. The bottom chord of the truss may only exist because it's part of the support system for the top chord and was never designed to carry any load or maybe just the evenly distributed weight of sheetrock. In that situation there is no safety margin for a storage rack because that load was never considered in the design in the first place.
 
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Old 03-14-21, 10:09 AM
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It appeared HVAC contractors removed some members to make room for an AC in the attic causing one of the remaining pieces to break.
I had thought that was the case because the initial pictures seemed to indicate that, but I was wrong. His followup photo showed no HVAC unit. Not sure what caused that truss to snap but IMO it was due to a poor grade of lumber that was used... it snapped right at/above a knot in the wood. Trusses should be structural grade and free of medium-large knots for this very reason. But that does show the amount of stress that trusses are under and why you should not overload them... as many people tend to do with storage. And why you should not bore holes through them .
 
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Old 03-14-21, 10:26 AM
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structural failures and buyer beware notices

While living in Colorado we had an epic spring snow of several feet (nearly 7 feet where I lived) and many buildings collapsed due to snow load. Some were recent construction too. Lots of old buildings obviously.

Wonder why truss manufacturers are not required to put some kind of warning or disclaimer on their products. I could see a label on the bottom cord that stated the load limits for attic storage or whatever. Also, some sort of set of papers included with new construction buildings that specified the Don'ts similar to what you see in nearly all manuals today for items plugged in. Or a lawn mower. Or most any item that can conceivably be misused. We are no longer a society of common sense minded people. Just ask a random selection of people to tell you the details regarding the engine if their car. There are many more things that can be done wrong in a home than just about any other item a person owns. Shouldn't we be required to warn homeowners or tenants of what they cannot do to the structure? Why should it be any different than a list of safety precautions on a space heater?
 
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Old 03-14-21, 10:51 AM
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Shouldn't we be required to warn homeowners or tenants of what they cannot do to the structure?
This is covered by building standards like getting permits prior to making any structural changes. 100+ year freak weather events are not typically covered by building codes any more than houses are built to withstand tornados. And every house in the US isn't built to Miami/Dade hurricane standards either.
 
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Old 03-14-21, 12:49 PM
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"This is covered by building standards like getting permits prior to making any structural changes."

Understood. However, building permits will not stop people from putting plywood or OSB in their attics and then moving too much weight up there. Anyway, I am still surprised there are not any modification limits or guidelines for homeowners.
 
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Old 03-14-21, 04:51 PM
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Yeah. Kind of like how there aren't any guidelines to tell you how much plywood you can safely stack on top of your car at Home Depot.

 
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Old 03-14-21, 05:30 PM
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Makes me wonder how often there are structural failures resulting from homeowner improvements?
It happens, but one of the benefits of using the materials we typically use, it can result in cracks, sagging, and structural issues, but it's rare you see a house collapse.

About a year ago, one of the older houses in the area (late 1800's stone house) had the entire front section collapse. Discussing with a local PE (not consulting on that failure) mentioned the scuttlebutt was that a contractor was doing work in the house and was't re-supporting something right. He mentioned that with wood, you often hear the creaking, cracking, and slow movement as it fails. With stone, it just goes. Luckily, no one was hurt.
 
 

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