Things to Watch For in an Installation (Problems to Avoid)

There are two main things to protect against the fastener pulling out of the wall, or breaking off. Pull out relates to the tension and breaking relates to shear.

Manufacturers have tested their fasteners and rated them for light, medium, or heavy duty. In addition, tables are available from the manufacturers which list the type of fastener, and how strong each diameter of that type of fastener is in tension and shear.

Both of these can be avoided by knowing the weight of the item to be mounted and what it is going to be mounted upon. This information can help determine the size and number of fasteners to be used.

There are trade offs here. It may be that 2 larger fasteners make more sense than 4 smaller ones, but smaller fasteners mean smaller holes and faster drilling and perhaps a more even support of the object such as would be the case for shelving.

Here are things to guard against:

Pulling out of the wall chemical or adhesive fasteners

Dusty hole.

Not removing the dust in a pre-drilled hole before injecting the adhesive can cause problems. The dust can be removed by either blowing it out or vacuuming it out. However, for small holes blowing it out is easier.

There are "blowers" specifically designed to accomplish this. They typically have a rubber bulb at one end and a thin tube at the other. The tube is inserted into the hole and the rubber bulb squeezed vigorously. This will force air into the bottom of the hole, which will lift and carry out the dust. (A dust mask is a good idea here).

An alternate method is to flush the hole clean with running water and then letting it dry out before injecting the epoxy.

Improperly sized fastener too small a diameter or not long enough.

The result of either of these is too small a bearing surface to resist the loads the item puts on fastener. With bonded anchors, this can cause the adhesive to separate from the surface of the hole (more likely) or from the fastener itself.

Pulling out of the wall expansion fasteners

Hole too large for the anchor.

This can happen if the wrong sized bit is used to drill the hole. The manufacturers instructions should be followed. If the hole is too large, then either not enough of the expansion portion will get to bear upon the sides of the hole, or it wont be wedged in firmly enough.

Improperly sized fastener too small a diameter.

If the hole size is correct and the anchor has been properly set, it could start to yield (stretch) if a heavier than designed for item is hung upon it. In this case, it actually becomes a bit narrower and can be pulled out. Many fasteners have been tested by the manufacturers and come with ratings for light, medium or heavy duty use.

Breaking off

If too small a diameter fastener is selected for the weight of an object, the bolt used to attach the object to the wall can be broken or sheared off. This can happen even if the hole has been properly drilled and the anchor set correctly (whether bonded or an expansion type).

It really is a matter of sizing the fastener to match the weight of the object being hung or attached. In earthquake country, its also a good idea to have the fastener a bit stronger than required to support the weight of the object. Vibration or motion induced by the earthquake puts an additional load on the fastener.

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