How to figure out if wood screws are big enough.

Factual Questions
1

Ok, so another of my hobby questions.

Say I want to hang a 150 pound sign from a wall stud with 4 or 6 screws. The sign will be on arms about 1 foot from the studs so they’ll be pull out force as well as shear forth. I can’t find a detailed answer as to what size of screws I need to be absolutely sure it won’t pull out and wreck an expensive antique sign some dark night… Answers online seem to be either “pretty much anything” to how to figure it out using calculus (which the last class I took was 15 years ago so my off-hand memory is about zilch).

Looking for either specific suggestions (such as #10 by 1" wood screw) or how to figure things like this out generally speaking.

2

This will help to get a definitive answer, but if I were doing it, I’d just use 3.5" #10 deck screws.

3

Is there anyway to use multiple studs? And how are the screw holes in the bracket(?) arranged? If they are side by side at all, you may have trouble getting the screws to stick into the same stud.

So theoretically I would use beowulff’s recommendation and go for at least 6 for a single brack or 4 each for two brackets. But get real screws (ask someone who knows) and not a cute box of the cheapest ones.

4

Because of the way the mounting is, the sign can only be mounted to one stud. The brackets will be 1-1/2 galvanized pipe flanges, so I could line up two of the holes on each to be vertical. If I had to I could add another stud right next to the existing one and probably fit all four holes of the flange into studs.

5

So there will be one arm, one foot long, that is supporting the sign? I assume this is inside the house? 150 pounds is pretty heavy, so here’s how I would do it:

Face plate, 2x6 by depth of sign (at least), which will be secured to the stud. Deck screws as beowulf suggests, two across every six inches should be enough. If you want no extra width on the face plate after the braces are installed, rip it down to 4-1/2 inches wide.

Before securing face plate to wall, attach support arm 2x4 centered at top of face place from the back of the face plate; no more than 3 deck screws strategically placed, more will weaken the support arm. The profile of the support arm will be vertical rather than horizontal; there will be 2 inches on either side of the support arm on the face plate (or 1-1/2 inches if you ripped down the face plate).

Make two 2x4 braces with angle cuts to go on either side of the support arm. The top angle will end up being horizontal, the side angle will end up being vertical; the two angles together should add up to 90 degrees. Attach the two braces at the top with screws to the support arm (or bolt through all three pieces); attach the two braces at the bottom to the face plate (you can screw from the back or the front, depends on how you want it to look; watch out for excess screw length if you screw from the back). Make sure the braces are plumb (i.e. vertically straight from the front).

Screw the whole assembly to the wall as in the second paragraph. Then, if you weigh more than 150 pounds, test it by hanging on it yourself, and bouncing a little. If it seems solid, hang your sign. If it seems to have any give at all, replace screws with lag bolts (and countersink them for a better appearance).

You can dress this up in a variety of ways to look good, paint being the easiest. If you’re ambitious you can countersink all the screws or bolts that show and put in wood plugs (which you can buy, or make with a plug cutter). If you pick a lower grade of lumber with knots etc. you can spackle those smooth before painting.

Voilá.
Roddy

eta: posted before I saw your second post. The method I described would be if you weren’t using metal brackets. If you do use metal brackets, I would still recommend testing it by hanging from it yourself. I wouldn’t be worried about the metal brackets coming out of the wall, but the support arm coming off the bracket. Not sure what size support arm you are proposing, you may need 4x4 instead of 2x4. That would still fit on the stud.

6

I’d look for a way to put a mounting board across at least two studs, then attach the sign brackets to that. Any one stud might split from too many screws. 150 pounds extended is a lot, I’d be looking at lag bolts not screws, or drill through the wood and use bolts with nuts. You want a pretty hefty mounting surface to hang a heavy sign like that.

7

Missed the edit window:

ETA: seeing your last post I’d really recommend against hanging that sign from one stud. Each pipe flange will put a lot of screws close to each other, weakening the stud. use a mounting board. roddy’s recommendation of a 2x6 sounds good, space your screws out along the stud and don’t let them line up, that could make the stud split.

8

This approach puts an enormous strain on a very small section of a stud that only has a width of 1.5 inches. You really need to spread the load a little.

A piece of 2 x 6 screwed to 2 or even 3 studs horizontally would provide a much stronger surface to work with. You can then use lag screws or even carriage bolts. If you use carriage bolts of course you have to attach the flange before you attach the 2 x 6 to the wall.

9

Nope, two arms, one on top and one on bottom of the sign.

10

In addition to the quality of the fastener, pay attention to the wood.

The big box stuff is not even cured - that is what “green” means - uncured, not good for anything, including firewood.

Good quality D.F. is still available. Depending on location, you may find yellow pine. Look at the ends of dimensional lumber - good stuff will have wax; cheap stuff uses paint.

With the advent of wall-mounted TV’s, you have info as to mounting heavy items on walls - look at how a 150 lb. TV mounts, compare the amount and type of fasteners the TV wants vs. what you are planning.

Stainless is stronger than mild steel; don’t buy anything serious at the big box.

We are now raising a generation of people who are not qualified to build a kid a tree house - or even a sand box. Pathetic.

11

The house was built in the 1960s, so that means it has yellow pine instead of the modern cheap stuff?

Would a better idea be buying some 4X4s or doubling 2X4s, attaching the top to the ceiling beams and resting the bottom on the cement floor, and then using lag bolts or really big screws in the posts rather than trying to use the existing wall studs? I’m worried about going too nuts with large fasteners in the existing wall since it’s a load bearing wall and is just 2*4s.

The signs have 2 holes for 1-1/2 inch galvanized pipe, one in the top and one in the bottom. They weigh 50-75 pounds each, I was going to mount one on top of the other, which leaves open the possiblity of having a third support between them if it would be a good idea.

12

To be let-the-baby-climb-on-it-while-drunk-unkle-chins-himself-on-it:

the the mounts all vertical?

Open wall, find quality 4x4’s (1 if vertical, use 2 with 2x6 notched into 2 for horizontal).

Use steel “L” brackets with deck screws - one on each side of the 4x4 post, secured with 2- #8x2 deck screws.
So far, none of the fasteners are loaded in tension.

You now have plenty of wood to drive screws, drill bolt holes without chewing up the studs.