It’s such a thing with dowels: There are so many of them that you can quickly no longer see the forest for the trees. But which dowel is the right one and when? The following overview creates order and shows all the common examples of drywall. Because with typical expansion anchors, you will not get any further with these walls. So which dowel is the right one for plasterboard or, better said, for drywall?
From dowels and walls
It’s almost as certain as the amen in church. The dowel supplied with the new piece of furniture does not fit 90% of the existing masonry. Because ordinary expansion anchors only hold in place with solid masonry or concrete walls. However, these are rarely found in today’s buildings. If hollow perforated bricks were used instead of or the interior work was carried out using dry construction, these dowels simply do not fit. Good advice is valuable now. But don’t worry, this article not only explains the various dowels that can be used in drywall, but it also describes how long the screws have to be and everything that has to be observed so that installation in the drywall is always successful.
But wait! Drywall doesn’t mean that the plasterboard is always laid. Correct! Fortunately, drywall anchors find a hold in each of the following materials. These are, for example, plasterboard, plasterboard, chipboard, plywood, and a few more.
It is essential to know that the load-bearing capacity of the walls of the individual dowels is mostly determined by the wall structure and the anchoring base (i.e., the cladding material). A plasterboard dowel made of plastic in a 12.5 mm thick plasterboard wall can hold up to 66 pounds. In a gypsum fiberboard of the same thickness, however, it can withstand up to 110 lbs.
There is not just one dowel for drywall construction, but several different types. These can be divided into the following groups:
- plastic dowels reaching behind
- metal dowels reaching behind
- Special dowels (spring dowels, toggle dowels, plasterboard dowels)
- Injection systems
With all the anchor types described – in contrast to expansion anchors – the load is transferred primarily through a form fit. This means that the dowel is held in position by knotting or spreading it behind the drywall. With ordinary expansion anchors, the anchor is held in place by friction (force fit).
Engaging dowels (plastic and metal)
There are several variants of plastic dowels that reach behind, namely those that are inserted without changing their shape beforehand, and those that have to be pressed together before assembly. Metal plugs that reach behind, however, must always be inserted without changing their shape.
With all of these dowels, the form fit is only created when the screw is screwed in. If the screw reaches the end of the dowel, the dowel becomes knotted, spread, or unfolded. In the case of plastic anchors, wood or chipboard screws are used, in the case of metal anchors, metric screws are used. With all dowels reaching behind, it is important that the collar of the dowel can support itself against the component. Otherwise, no form fit can be created when screwing in the screw.
Note: Setting tools are also used to expand metallic dowels. This is particularly advisable when installing on smooth surfaces, as in these cases, the claws of the dowel edge are pressed flat, and the dowel inevitably spins when the screw is screwed in. It is then no longer possible to spread the dowel with the screw.
Special dowels in drywall
In addition to the cavity anchors just described, there are also special drywall anchors for plasterboard that can be screwed into the walls without pre-drilling. They resemble a spiral dowel for facades or aerated concrete and are made either of plastic or aluminum. For assembly, these are screwed into the plate at the desired location with a screwdriver or cordless screwdriver. However, if the dowel is removed again at some point, a very large crater usually remains on the surface.
Note: Since a cordless screwdriver is always at hand, the additional effort to first drill a 0.23 inches hole for a cavity dowel is limited. When it comes to precision, drywall anchors are such a thing. Even if such a dowel seems practical, cavity or general-purpose dowels are probably a better choice.
The situation is different with a toggle or spring-loaded anchors, which are very popular in drywall construction, especially for ceiling mounting. These are mostly made of metal and are sold as a complete element. The folding mechanism is triggered automatically by a spring in the case of the hinged anchor or mechanically by gravity in the case of the hinged anchor. The dowels are completely inserted into the drilled hole and finally locked by partially pulling them out. Of course, these dowels can also be used in the drywall as well as in hollow bricks.
The last group of dowels, which are rarely used in drywall construction, are so-called injection systems. These are mainly used when really heavy loads are to be attached, such as railings, fall protection, and the like. However, since heavy loads are only mounted on trusses in drywall construction, the use of such dowels is generally not necessary or too expensive for the intended purpose.
In principle, injection systems work in such a way that a mesh sleeve is inserted into the borehole, which is then filled with injection mortar. Then a threaded rod also called an anchor rod, is inserted. When it is inserted, the injection mortar is pressed out of the mesh sleeve. The mortar displaced in this way then forms a form fit on the back of the drywall after it has hardened.
Choosing the right drywall anchor
Which drywall anchors are ultimately used always depends on the expected load and the substructure. The loads that plasterboard walls or walls with gypsum fiber cladding can withstand have already been discussed in the linked articles. Light bracket loads of up to 88 lbs per meter of wall length are generally not a problem. Medium console loads of 88 lbs to 154 lbs require a little more planning and caution.
The choice of plastic or metal dowels for plasterboard is already relevant for light bracket loads. For example, a plastic anchor with plasterboard with a thickness of at least 1/2 inches holds approx. 44 lbs, whereas metal anchors, hold 66 lbs. In the case of gypsum fiberboards, however, this plays a rather subordinate role. Even plastic anchors for gypsum fiber boards of the same thickness carry around 110 lbs per anchor.
Dowel size: how big can it be?
Drywall anchors come in different sizes. The most common are 1/4, 1/3, and 1/2 inches. When considering which dowel size is best to use, there are also recommendations. These are based on the one hand on the severity of the bracket load and, on the other hand, on the existing panel thickness.
* Medium-weight bracket loads must not be attached to plasterboard walls with a thickness of fewer than 1/2 inches. In the case of plasterboard, however, 1/4 inches or 1/3 inches thick dowels can be used.
For walls up to 1/2 inches thick and with light bracket loads, 1/4 inches thick dowels are usually sufficient. For most items such as pictures, mirrors, and light shelves, these are generally useful. If, on the other hand, medium-weight bracket loads are to be attached, 1/3 inches thick dowels should be used. Only with thick or double-clad drywall does it make sense to use 10 mm or 12 mm thick metal dowels of the appropriate length to ensure optimum hold. However, this does not mean that 10 mm thick dowels would not find a hold in thinner walls.
Screw length and screw diameter
If the screws are always supplied with metal cavity wall plugs, this is not always the case with plastic wall plugs. How big and, above all, how long do the screws have to be so that the drywall anchor is held securely? The question of the optimal length is easy to answer. As has always been known from expansion dowels, the screw with cavity dowels must be longer than the dowel by at least the screw diameter plus the thickness of the washer and the thickness of the connecting structure or component. For metal wall rails and similar fastening methods, this is usually around 10 mm. This is the only way for the screw to reach the end of the dowel and to knot the cavity dowel or create the form fit.
The diameter of the screw depends entirely on the thickness of the anchor. The following table can be used as an overview, whereby the information provided by the anchor manufacturer must always be observed in individual cases.
When installing on the plasterboard, one thing must be observed: the holes must be drilled! Piercing with a screwdriver or other object can be done mechanically, but it is far from a good idea. Because this causes the drywall to break out on the back, and there is a huge gap where the dowel is supposed to be held by knotting. The stability is then no longer guaranteed.
It should also be said that all plastic anchors are only suitable for pre-positioned installation. The dowel is pushed into the hole, and the component to be fastened is stopped and screwed on the outside. If the push-through installation is required, metal drywall plugs must be used.
If metal cavity dowels are used for the installation of wall cabinets in the bathroom, the problem usually arises that the dowel cannot be expanded with the screw, since the lugs under the dowel strip are pressed flat. Even if the drill hole is too large for these dowels, the lugs will not find a hold, and the dowel will not expand when the screw is screwed in. So drill exactly and spread with a set of pliers on smooth surfaces!
Once you have an overview of the types of dowels available, you will conclude that it is not as complicated as it seems at the beginning.
Because for light loads and the assembly of everyday objects, 6 mm thick cavity dowels are usually sufficient. If heavier objects are to be installed, metal cavity anchors will generally be used. And hinged wall plugs are probably the best choice for ceiling mounting. Sometimes it can be that easy!