Hanging it: weight, wall, hardware and height

Weight first, then the wall, then hardware chosen from a published rating for that wall and that weight. This chapter works the hook height back from a center height you choose, and says what to check once the picture is up.

1. What it weighs Understand

Everything in this chapter is downstream of one number, and most people guess it.

Glass is the mass, and it is well published. A trade association's table gives flat glass at 1.6 pounds per square foot at an eighth of an inch, 2.4 at three sixteenths and 3.0 at a quarter inch, with a density of 158 pounds per cubic foot for anything not on the table. Picture framing glass is usually 2.5 mm, which the same table gives at 1.2 pounds per square foot. Product-specific

Nobody publishes moulding weight per linear foot, and nobody publishes board weight per square foot. So the weight box builds the rest from stated assumptions and prints them beside the answer: a frame section of the width and depth you type, at an assumed density for wood, composite or an aluminum extrusion, and a board allowance per square foot. Those allowances are ours, they are labelled as ours on the page, and the honest alternative beats all of them: put the finished piece on a kitchen scale.

Three rules of thumb that fall out of the published figure. A 16 by 20 inch piece with 2.5 mm glass is about 2.7 pounds of glazing. A 24 by 36 is about 7. A 30 by 40 is about 10. Add the frame and boards and a large glazed picture is a real load long before it feels like one in your hands.

When to get help. A national institute's lifting equation sets a load constant of 23 kilograms, about 51 pounds, described as safe under ideal conditions for 75 percent of females and 90 percent of males, and reduced by six multipliers for horizontal distance, height, lift distance, frequency, twist and grip quality. A framed picture held away from the body at arm's length is not ideal conditions, so the practical rule is lower than 51 pounds. A conservation institute's handling note is blunter about why: most damage to paintings and their frames occurs during handling, and the commonest causes are underestimating the weight of a framed painting and not seeking help, since most paintings, even easel-sized ones, require two handlers and a spotter.

2. Which wall is it

Every rating in the next section is a rating for a named wall. If you do not know what the wall is, nothing applies.

Plaster and lath, specifically. A federal preservation brief describes what is actually behind the surface: three-coat plaster has a scratch coat and a brown coat at about 3/8 inch each, with a finish coat a mere 1/8 inch thick, applied over wood lath nailed at right angles to the studs, over metal lath, or over perforated gypsum board lath. Plaster was the wall surface chosen for nearly all buildings until the 1930s or 1940s. That structure is why an anchor designed to expand behind a 1/2 inch sheet of gypsum board behaves differently there.

Finding the studs. Studs are commonly spaced 16 to 24 inches on center, a figure a federal museum leaflet states and which appears in the building code table a municipal building authority reproduces, with spacing columns of 8, 12, 16 and 24 inches on center; a state rule adopting the code shows the same columns. A stud finder is a guide and not proof. Confirm with a small pilot hole somewhere inconspicuous before committing.

3. Hardware by published rating

This is the part of the subject where real published numbers exist, and the way to use them is to divide.

Every anchor maker publishes an ultimate test figure and tells you to use a quarter of it. One maker's published questions page states that it lists the ultimate load each anchor sustained in independent laboratory tests, that industry safety standards recommend a quarter of that ultimate load as a reasonably safe working load, and that it cannot guarantee even that, because it does not know the condition of your wall or exactly how you are anchoring the load. A masonry screw maker's technical notes put the same rule as safe working loads for a single installation under static loading not exceeding 25 percent of the ultimate capacity. Convention

That quarter is the single most useful fact in this chapter, because it converts a big number on a package into something you can divide.

Walls and hardware has the full table with the conditions each figure assumes, and the hardware box does the division for you and prints the conditions beside the answer.

Three conditions that travel with every number.

First, the thickness. A drywall figure is for one thickness, and the same anchor in 9.5 mm and in 15 mm drywall is two different numbers, sometimes differing by a factor of two.

Second, the distance from the wall. The same maker makes the point almost nobody else does: the ultimate value is for objects held close to the wall, and moving objects away from the wall, such as the far end of a shelf or a mount that swings out, significantly increases the effective weight and greatly reduces the allowable load. A picture hangs close. A projecting light or a swing-arm does not.

Third, the cavity. A toggle needs room behind the wall to open: one sheet gives a minimum clearance behind the wall of 1-7/8 inches, and a plastic toggle 19 mm. If there is insulation, a pipe or a stud behind the hole, the anchor cannot deploy.

The gap between a technical sheet and a package. It is worth seeing once. The same maker's product page says its toggle supports up to 238 pounds in 1/2 inch drywall, with no safety factor mentioned anywhere on the page. The technical bulletin gives 238 pounds as the ultimate test figure and says to use a quarter of it. Same number, two meanings. Use the bulletin.

The margin rule. A practitioner guide prepared with a museum packing and handling network gives the only published margin rule for frame hardware found in this research: as a general rule, hanging hardware should support 25 to 50 percent more weight than the maximum weight of the artwork, and it adds that it is critical not to guess here and that all methods should be re-checked annually.

Two hooks: the disagreement this manual will not resolve. A hanging hardware maker states that its strap hanger is rated at 150 pounds per hanger and holds up to 300 pounds with two. A picture rail system maker prints that its maximum weights can be doubled when using two hangers and hooks per picture, footnoted with two conditions: that the rails are fastened securely into wall studs, and that the load sits evenly distributed on both hooks at all times. Against that, an adhesive hook maker's own position, relayed through retailers, is one hanger per frame with ratings that are not cumulative, and a retailer's answer from another hardware maker says its ratings are not cumulative and that weight is rarely distributed evenly. No engineering or standards source in this research states a general rule either way. So the calculator does not add two ratings together, and this manual's advice is: if one fixing at a quarter of ultimate does not cover the weight, use a bigger fixing or a stud, not a second hook.

4. The hardware on the back of the frame

The wall side of this subject has published test data. The frame side does not, and that difference is worth stating plainly.

No tested rating for a D-ring, a screw eye or a strap hanger could be found in this research. The ratings that circulate sit on retail listings, disagree with each other for what appears to be the same part, and state no test basis; one maker's answer on a retail listing says the ratings assume the hanger is nailed into a stud and are for comparative purposes only, and that they are not cumulative. Ask the authority

No rated standard for picture wire was found in this research. The gauge tables that circulate are supplier charts that disagree with each other, and the chart they appear to come from could not be retrieved. One trade supplier states only this, which is the honest version: always use a wire with a tensile strength at least double that of the weight of the picture. Note that a wire sold as a "10 kg" wire is being described by its maximum picture weight under that convention, not by its breaking strength.

What the practitioner sources do say about method, consistently:

• Two points rather than one. A museum conservator's household advice is not to hang a painting on one nail, but to attach two D-rings, one each side of the frame, onto matching hooks, with hardware rated for the weight. An art school's gallery sheet uses two D-rings and two hooks as its default rather than a wire over one hook. A federal leaflet says that when hanging wide pictures, two suspension points may be desirable.
• D-rings over wire, for anything that matters. A practitioner guide says D-rings used with wall hooks are more secure than wire used with wall hooks, and lists the drawback of wire plainly: artwork can shift or slip on the wire.
• Not saw-tooth hangers on the top rail, which a conservation center rules out for anything it is specifying.
• Not on the frame edge. A museum educator's slides put it among the things not to do: do not hang on a frame edge, because it can fall off the wall and damage the frame.

Rail systems are the exception that publishes. One maker's table gives per-component capacities: tracks from 12.5 to 110 pounds per foot depending on the type, stainless steel cable at 45 pounds, nylon cord at 15, hooks from 12 pounds for a mini hook to 110 for a gallery classic. Another publishes a rail at 45 kilograms per metre with three fixings per metre, and hook-and-cord combinations at 4, 10, 15 and 20 kilograms depending on the cord. If you are hanging a changing wall, a rail moves the load question from the plaster to the fixings that hold the rail, which is usually an improvement.

5. Height, and where the figures come from

The arithmetic is published and the height it works from is a convention. Keep those two apart.

The formula, published by two institutions in the same shape: half the frame's height, minus the drop from the top of the frame to the taut wire or the D-ring, plus the center line. A museum educator's slides work it as a 30 inch piece with hardware 5 inches down, giving 57 plus 10, so the nail goes at 67 inches. An art school's gallery sheet works it at 58 inches with two D-rings, measuring the distance between the D-ring centers and marking two points that far apart on a level line.

The center height, and the honest state of it. Four institutions publish a figure and they disagree.

And the body whose guidance is of standards character publishes different numbers, lower, for a different reason. A national museum's accessible exhibition design guidelines say to mount small items at no higher than 1015 mm (40 inches) above the floor to the center line; give a male adult wheelchair user's average eye level as 1090 to 1295 mm (43 to 51 inches); note that objects placed above 40 inches will be seen only from below by most seated and short viewers; and say that wall labels mounted between 48 and 67 inches are comfortable for both seated and standing viewers, with a 54 inch center line optimum for everyone. It also gives a child wheelchair user's eye level at about 41 inches, and children's eye level as 8 to 12 inches below an adult's for pre-kindergarten and 12 to 17 inches below for kindergarten and older.

So: 57 or 58 inches is a convention with several named institutional publishers and no standard behind it, and the one source writing accessibility guidance puts the useful band lower, because it is thinking about people the convention does not consider. Convention

This manual's position is therefore that the center height is an input, not a rule. The hook height box takes whatever you choose and prints the accessibility figures beside the result. If your household sits in that room, or uses a wheelchair, or includes children, the accessibility figures are the better guide and the convention is the thing to adjust.

6. Doing it safely

Four things, each with a published basis.

Eye protection. The federal workplace rule requires eye protection that provides side protection where there is a hazard from flying objects, and names the consensus standard editions it accepts: ANSI/ISEA Z87.1-2010, Z87.1-2003 and Z87.1-1989 (R-1998). Worth knowing that the consensus standard itself has moved on since, which is a divergence rather than an error; impact-rated protection with side shields is the thing to buy.

Ladders and step stools. The same federal body's construction rule gives the setup angle for a non-self-supporting ladder: the horizontal distance from the top support to the foot should be approximately a quarter of the working length. Both its rules say the top or top step of a stepladder must not be used as a step, and one adds that the cap must not be either. A standards-developing trade association gives the household half: the ladder's duty rating must exceed the total weight of climber, tools and supplies; the climber must face the ladder with two hands and one foot or two feet and one hand in contact at all times; maintain three points of contact while working; keep the center of your belt buckle between the side rails rather than overreaching; one person at a time; clean slip-resistant shoes; and place the ladder on firm level ground.

Two people. The load constant above, 23 kilograms or about 51 pounds under ideal conditions, with six multipliers that reduce it. A conservation institute's handling note adds the practical version: plan a safe uncluttered route, prepare a padded place to put the work down before you lift it, remove dangling jewellery and bags, handle one painting at a time, and do not squeeze between furniture, because navigating sharp corners can easily pierce a canvas.

Broken glazing. Treat it as a hazard. One institutional procedure says broken glass is not handled with bare hands and must be collected using appropriate tools, into a sturdy cardboard box of a size that will not weigh more than 40 pounds when full, sealed with packing tape rather than folded shut, and labelled. Tape across a cracked sheet before moving the frame, wrap the pieces, and keep children and pets out of the room until the floor has been gone over twice.

7. Checking it after it is up

Five minutes, once, and then once a year.

• Level it properly. A museum educator's slides say what everyone learns eventually: eyeballing will betray you. Use a level, and check the frame rather than the image.
• Push gently at the bottom edge and see whether the piece pivots on its fixing or sits back against the wall. Pads at the lower back corners, which the trade specification asks for at 3 mm thick, keep it off the wall and let air move behind it.
• Look behind it once. If the wall is an outside wall, the back of the frame is where condensation will show first.
• Write it in the hanging plan: the wall, the weight, the hardware and its rated load, and the date. In three years that row is the difference between knowing and guessing.
• Put a date in your calendar. A practitioner guide says all hanging methods should be re-checked annually. The yearly check is the list.

9. See it See it

• Frequently asked questions, an anchor maker: the quarter-of-ultimate rule in the maker's own words, and the point about load held away from the wall.
• Techniques for hanging and presenting art, an arts commission with an art museum: the hook arithmetic worked, the hardware list, and the things not to do.
• Guidelines for accessible exhibition design, a national museum: the only agency-grade viewing heights found, and they are lower than the convention.
• Fabricating secure hangers for framed works of art, a federal museum leaflet: the interlocking L-hook arrangement, with its anti-earthquake purpose stated.

10. Practice Practice

Minimum: one piece weighed, one wall identified, one fixing chosen from a published rating. Time: about 45 minutes. Materials: a kitchen or bathroom scale, a tape measure, a level, a pencil, a stud finder if you have one, and the hardware's own packaging.

1. Weigh it. Stand on a bathroom scale holding the framed piece, then without it, and subtract; or put a small piece on a kitchen scale directly. Write the number in the hanging plan.
2. Identify the wall. If it is drywall, find its thickness at a switch plate or an outlet cover. Every anchor rating depends on it.
3. Find the studs and mark them lightly in pencil. Confirm with a pilot hole in a place that will be covered.
4. Choose the fixing with the hardware box. Copy the rating and its conditions into the hardware sheet. A number without its conditions is not a rating.
5. Mark the hook height with the hook box. Hang it, level it, and fill in the row with the date.

11. Your pictures Your pictures

12. Check your work Check your work

Criteria

• The weight is measured or calculated, not guessed.
• The wall is named, and for drywall its thickness is known.
• The fixing's published rating is written down with the conditions it assumes.
• The working figure is a quarter of the ultimate, and the weight is inside it with the 25 to 50 percent margin.
• The piece hangs level, sits back on its pads, and has a row in the hanging plan with a date.

Worked example

Yusuf Ferrante (fictional) has a 30 by 40 inch canvas and a lease that forbids anchors larger than a picture nail. The canvas has no glazing, so the weight box gives about 6 pounds and his scale confirms it. The stud finder puts studs at 16 inch centers and one of them is 3 inches from where he wants the left edge. He hangs it on two picture nails into that stud and its neighbor, which is within the lease and gives him two points rather than one. The 22 by 28 inch textile is a different problem: it is going on the only interior wall, the apartment is humid in summer, and the textile is glazed with acrylic and spacers, so the weight box gives about 5 pounds. Same fixing. He writes both rows, with the lease condition noted, so a future tenancy question has an answer.

Common mistakes

• Reading the package number as the working load. It is usually the ultimate figure. Divide by four.
• Using a drywall rating on plaster. Different material, different behavior, and the rating does not transfer.
• Adding two hooks together. The makers themselves disagree about whether that is allowed, and no engineering source in this research settles it.
• Trusting the stud finder. A guide, not proof. A pilot hole costs nothing.
• Hanging on a wire over a single nail for anything that matters. Two points, D-rings rather than wire, and hardware rated for the weight.
• Eyeballing the level. It betrays you, and on a group it betrays you visibly.

What is still unresolved

• Where a group goes and how it is spaced: Arranging pictures.
• Whether the wall is one the piece should be on: Where it can hang.
• What to check in a year: The yearly check.
• What a D-ring is actually rated for, which nobody publishes with a test basis.

13. Knowledge check and scenario

Checklist

• The framed weight measured or calculated and written down.
• The wall identified, with drywall thickness known.
• The fixing chosen from a published rating, at a quarter of ultimate, with its conditions copied down.
• Hook height marked from a chosen center height, and the piece levelled once up.
• Seismic or security hardware considered where it applies. (Go deeper; optional)