Every day... somewhere... something near and dear falls off someone's wall or ceiling! To that end we offer this collection of information, a primer as it were, of experiences and common sense to help you keep YOUR wall hangings where they belong!
(Even if you think you know everything there is to know about anchors, there may be something here for you, too!)
What is an anchor?
An anchor is a fastener that can attach one object to another in situations where screws, nails, adhesives or other simple fasteners are either impractical or ineffective. Two common surfaces where anchors are useful are 1) on extremely hard surfaces such as concrete and 2) on hollow surfaces such as doors, walls and ceilings...especially where there is no convenient wood stud or beam behind the surface.
There are many styles of anchors, each one having different strengths and weaknesses... literally! An anchor that is strong installed in drywall may not be as strong in concrete. Or visa versa! Perhaps the biggest problem with anchors is almost all of them "feel" strong when first installed. Over time, though, an anchor that is mismatched to the wall material will eventually loosen up causing damage to the wall, your hanging and whatever was underneath it!
This confusion is compounded by manufacturers who sell towel bars, small cabinets and other "hung" items with anchors that are not strong enough for the job. In the interest of "economy", the least expensive anchors are sometimes included with no instruction concerning safer, alternate mounting methods.
How much weight can an anchor hold? That depends on how much you trust my disclaimer...
Trying to pin me down, huh? I wish I could tell you with precision, but the strength of any anchor is subject to a number of variables, such as 1) the type of object being hung, 2) the type of surface the anchor is installed on, 3) the condition of the surface... and, of course, 4) the type of anchor!
For example, you might successfully hang a 25 lb wired mirror onto a screw in a plastic expansion anchor (in drywall) where the force in downward. The same anchor and screw might not be able to support a 25 pound cabinet if the cabinet tends to pull the anchor outward. It's all relative. Strength, that is.
I will be including some load data on each type of anchor, but take this more as a measure of relative strength between the types of anchors... not a rule or firm guideline! If your wall is structurally weak, has been repaired, has water damage, etc., it is impossible to know the true strength without on-site testing. Of course, that's up to you 'cause you're there and I'm way over here!
Types of anchors and their uses...
All anchors can be divided into two basic types... expansion anchors and hollow wall anchors.
1) Expansion anchors are used in thick, solid materials... concrete, brick, mortar, metals or even wood. They work by expanding when a screw or bolt is threaded into them. If you remember anything about expansion anchors, remember this...
Expansion anchors are only as strong as the material they are installed in.
If an expansion anchor is installed in a soft material (such as drywall), it may appear to be strong but don't be fooled... the strength is minimal and it will eventually loosen and/or pull out if too much stress is put on it.
2) Hollow-wall anchors, on the other hand, will not work in solid materials. Instead, they are designed to be used in thin materials or on hollow walls. They each have a unique way of spreading within the hollow of the wall. Once spread, the anchor cannot be pulled back through the smaller installation hole. The strength of a spreading anchor is proportional to the size of the "spread"!
Those are the basics... now lets look at some specific anchors from the least strong to the most strong. We will investigate specific concrete anchors in another article.
Plastic (and other) expansion anchors
Plastic expansion anchors are one of the most commonly used... and abused... wall anchors. They are available in a number of sizes and designs (see graphic). Larger plastic anchors will accept larger screws and therefore have greater holding capacity. The more heavily "ribbed" anchors will give the greatest gripping strength, regardless of the wall material.
When a screw is installed into a plastic anchor it expands, exerting force against the material it is installed in. As with all expansion anchors, they are strongest when used in a solid material, such as concrete. Their strength is even limited in concrete, though, because plastic is not indestructible... hence they may pull out because of anchor breakage! (For this specific application there are expansion anchors made of lead... there is one in the graphic above in the upper left corner. More in a future article on concrete anchors!)
Installing a plastic anchor is a matter of first making a hole for the anchor in the surface. This can be done with a drill in hard materials, or an awl in drywall. I have always preferred using an awl in drywall since there is no dust produced. However, if you prefer using a drill choose an old, worn drill bit if you have one available. Drywall is very abrasive and will dull a good drill bit!
Then just press the anchor into the hole until it is flush with the surface. It is preferable that the hole be slightly smaller than the maximum width of the anchor so, if necessary, tap the anchor flush with a hammer. Caution here... if the hole is too small the anchor will collapse when you tap it in!
Overall, plastic expansion anchors are the least strong of all the anchors discussed here, with actual pull-out strength of around 30 pounds in concrete but as little as 10 lbs in drywall (depending on the anchor and screw size).
Unfortunately, many people use plastic anchors in drywall when they shouldn't.
When can you safely use a plastic anchor in drywall?
When the load is light and the force is perpendicular to the anchor. You can hang rather heavy pictures or mirrors using plastic anchors, placing the wire or picture hanging hooks onto the anchor's screw. Use two anchors and screws whenever possible... the additional strength is desirable plus doing this is good picture hanging practice, anyway. Ask any professional picture framer!!
To "steady" or stabilize a wall hanging that is being held up primarily by another, stronger anchor. This method of hanging is useful on towel bars or curtain rods that have two closely-spaced holes. Use a strong anchor such as a toggle in the top hole and a plastic anchor in the bottom hole. (More on this issue under "toggles").
Never use a plastic expansion anchor in a ceiling under any circumstances unless you are hanging something extremely light, such as a smoke alarm! You will be sorry!
Removing an expansion anchor...
If it didn't already pull itself out... insert a screw partially into the anchor and pull it out. Wiggling while pulling may help free up the anchor. THE SCREW, I mean!
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