Using several screws that are #4 or larger into a wall stud can hold up to 100 pounds or more. You want to make sure they can go at least 1 inch into the stud to be secure. If you are hanging a shelf that will have books on it, this is the perfect hardware.
A screw in a stud can hold between 80 and 100 pounds. Be sure to distribute the weight across as many as you can. The easiest way to increase the amount of weight a screw in a stud can hold is to simply double up.
When standing vertically, such as when it functions as a stud, a 2×4 can hold about 1,000 pounds. A 2×4 can hold up to 40 pounds or 300 pounds when laying on its edge without sagging when laying horizontally.
Zach Eyman: "A good rule of thumb is 80 pounds for a single stud, but a specific mount's specifications should always be followed." Eighty pounds, as we'll see later, is pretty much everything below 60 inches.
If a joist is running perpendicular to the wall, or happens to fall directly above/below the wall, it can be load bearing. If there's a single top plate, the wall most likely isn't load bearing, unless the wall uses deeper studs than 2x4 (such as 2x6).
Hanging Something Heavy on Brick/Masonry
BobVila.com recommends a polyethylene expansion anchor. To install, use a masonry drill bit to drill a hole into the mortar where you want a hook to go. Then insert the anchor into the hole and screw the hook into the anchor.
Horizontally, a 2×4 can hold a uniform load somewhere between 20 and 40 pounds per linear foot depending on many factors like species, grade, load, and span.
Of course, studwork can be used for load-bearing walls — in timber framed homes, timber stud walls are used everywhere.
As we've discussed above, a 2x4x8 can weigh between about 9 or 17 pounds depending on the wood species, length, type, and moisture content.
A nail is drywall is only able to hold a few pounds at most and should not exceed 10 pounds of weight. To can significantly increase the weight capacity by using drywall anchors or nailing into a stud.
A thin nail in a wood stud can hold up to 20 pounds and several coarse threaded wood screws in wood studs can hold up to 100 pounds or more.
A 2×6 will hold 4 pounds per linear foot horizontally and 53 pounds per linear foot on its edge. Vertically, a 2×6 will hold between 662 and 998 pounds or over 7000 pounds when in a blocked and sheathed wall. However, many factors affect the amount of weight a 2×6 will hold.
A 2×4 can span a maximum of 6' 7” when spaced 16” apart and used as a floor or deck joist. When used as a ceiling joist or a roof rafter, a 2×4 can span up to 7' 3” spaced at 16”, and 6' 4” when spaced 24” apart. Due to the small spans of 2x4s, they often are not used in horizontal load-bearing capacities.
A 4 in. x 4 in. x 10 ft. timber can weigh approximately 31 pounds when it is completely dry (no moisture content) and weigh between 41 and 48.5 pounds when the timber is new pressure treated for above or below ground.
Look for joists or steel beams in your crawl space or basement. If there's a wall that runs perpendicular and there are joists, you'll know a wall is load-bearing. However, it's probably not load-bearing if the wall is parallel above the beams or joists.
Load-bearing walls are usually solid, whereas stud partition walls are hollow. But, this isn't always the case, so don't use this as your only check!
Many people assume that if a wall is constructed with timber studs then it is non-load bearing, this is not always the case. Load-bearing walls usually have posts, supports, or other walls directly above it.
A 4×4 horizontally spanning 8-feet can typically carry 500lbs safely in the center, and 1,000lbs spread evenly across the span before sagging excessively. Properly supported at 16” centers, and it can support up to 4,000lbs.
When used vertically, 4x4s are stronger than two 2x4s. However, if you need a horizontal surface, two 2x4s will be stronger than one 4x4. A 4x4 should not be used horizontally for anything structural. Always be sure that you're using the proper size and strength of lumber.
So if a double 2x4 has bending strength of (3")*(3.5")^3 = 128.6, then a single 2x6 has (1.5")*(5.5")^3 = 249.6. This means a single 2x6 is almost twice as strong in bending as a double 2x4.
How much weight can drywall hold without a stud? Typically around 20 pounds. For heavy items, you may need to double up or hang from a stud. With a cheap plastic wall anchor, like the ones most products include in the box, drywall can hold about 20 pounds.
For pictures that weigh between 5 and 20 pounds, a good option is plastic drywall anchors and for pictures between 20 and 50 pounds, you can use a metal wall anchor or make sure to use a wall stud. For anything heavier, or a good all around solution for hanging multiple pictures, use a rail cable hanging kit.
Instead, use a threaded drywall anchor to securely hold objects between 10 and 25 pounds such as heavy picture frames, bulletin boards, mirrors, and light-weight shelving. No power tools are required for this self-drilling fastener. Use a screwdriver to screw it in until it's flush with the wall.
You can calculate the typical span by multiplying the depth of the lumber by 1.5. For 2x4s, this would equal 6 feet, but that is only a general calculation. When used as floor or deck joists, the maximum span for a high-grade 2×4 is around 6' 2” for 16” spacing using Southern Pine depending on the other factors.
A rule of thumb is 1.5 times a joist's depth but in feet when spaced at 16” centers. In general, a 2×8 will span 1.5 x 8, so 12-feet. Based on all factors though, a 2×8 joist span is 7'-1” to 16'-6”, and a rafter 6'-7” and 23'-9”.