Table of contents:

Dowel properly: The best tips and tricks
Dowel properly: The best tips and tricks

Video: Dowel properly: The best tips and tricks

Отличия серверных жестких дисков от десктопных
Video: Dowel Joinery Technique and Tips | Woodworking 2023, January
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There are some things you can do wrong when dowelling - but only a firm connection between the dowel and the wall keeps heavy objects such as a wall cabinet permanently and securely in place. In this guide, you can read how to properly anchor and what you can do if the dowel does not hold.

Table of contents Table of contents Correct dowels: Firm hold on every wall

  • The main types of dowels
  • The different types of installation
  • Which dowel is the right one?
  • What load can the dowel hold?
  • Which screw fits the dowel?
  • Drill dowel holes correctly
  • The most common problems

Table of contents Table of contents Correct dowels: Firm hold on every wall

  • The main types of dowels
  • The different types of installation
  • Which dowel is the right one?
  • What load can the dowel hold?
  • Which screw fits the dowel?
  • Drill dowel holes correctly
  • The most common problems

A picture, a shelf or even the sink - many things in the house are screwed to the wall using dowels. In order for everything to stay safe, three things have to fit together:

  • Material texture of the wall
  • Type and size of the anchor
  • Type and size of the screw

The main types of dowels

As different the individual requirements are, so different dowels are offered by the market. The most common are universal anchors, but there are many more.

You can use universal dowels in any wall, regardless of whether it is made of plasterboard, concrete, aerated concrete or other material. They spread or knot in any surface and thus ensure a firm hold - even with cavities behind the wall. Important: The drill hole for the plastic dowels must be deeper than the dowel length so that the screw emerging from the rear has enough space.

Universaldübel für jeden Untergrund
Universaldübel für jeden Untergrund

You can use universal dowels in any wall.

Photo: Fischer

Expandable dowels also solve many of the usual fastening problems. They expand as soon as a screw is screwed into them. They are pressed firmly against the masonry in the borehole and are securely held with their profiled surface. The screw length corresponds to the anchor length.

Insulation plugs are very similar to plasterboard plugs. They can carry lighter objects and are also screwed directly into the ground without drilling. If present, the plaster above must be removed.

The spring dowel, also called tilting dowel, is used particularly often when hanging lamps or other objects on ceilings suspended with plasterboard. The two metal wings of the dowel sit on a thin threaded rod and open on the other side of the borehole using a spring mechanism. The spring dowel is locked on the underside of the ceiling with a washer and a nut so that it can no longer move. An eyelet or a hook can then be screwed onto the lower end of the threaded rod.

Shelves and other objects that are supposed to lie directly on the wall are often fastened with frame anchors by push-through installation. Drilled into the wall through the pre-drilled hole in the object to be attached. The frame dowel is inserted through the hole in the assembly part into the drill hole and is in contact with the component with the shaft end. Then you screw in the screw - it pulls the object firmly against the wall.

With plasterboard you can save drilling, because you drill the dowel directly into the wall to which something is to be attached. However, in order for them to be placed correctly, it is helpful if you pierce a small hole with a metal mandrel. Plasterboard dowels are mostly made of metal, but there are also variants made of solid plastic.

Gipsplattendübel
Gipsplattendübel

Plasterboard dowels are screwed directly into the wall.

Photo: iStock / kennjin

You don't screw a screw into a nail plug, but drive in a special nail screw. It spreads the dowel so that it sticks. Nail dowels are quicker to install than dowels with screws, but they offer less grip and are therefore more suitable for fastening lighter objects.

Gas or aerated concrete is a very soft building material, not every dowel finds the necessary hold here. Gas concrete anchors therefore have large, sharp-edged wings arranged on the outside like screws. They are driven into the borehole with a hammer and cut themselves into the soft material. After the screw has spread, a secure connection is created.

Brass anchors are a special type of expansion anchor. They are particularly robust and are therefore mostly used to fasten large and heavy components such as control cabinets and units.

Heavy-duty dowels are usually made of steel and have a cone with an internal thread at the end of the sleeve. Heavy-duty dowels are usually installed with threaded rods or long metal hexagon screws, which have to be precisely matched to the respective dowel in terms of their length and thread diameter - they are therefore usually sold as a set. When the screw end is screwed into the cone and the head rests against the wall or the component, it pulls the cone into the metal sleeve, which is divided into two at the end. This spreads out and creates a very firm and resilient connection. Heavy-duty dowels should preferably be installed in concrete and must have a certain insertion depth because they exert a very high pressure on the surrounding material.

This special form of dowel contains a resin-sand mixture in a glass cartridge. If an anchor rod is screwed in, the cartridge bursts and the anchor rod is chemically connected to the concrete or natural stone.

Verbundankerstangen
Verbundankerstangen

A compound anchor ensures extremely good fastenings in concrete.

Photo: Fischer

Dowel correctly: The different types of installation

Depending on the project, there are three different techniques for fixing objects to the wall with dowels.

The so-called pre-positioned installation is the classic form of dowelling and is used most often. You first drill the hole in the wall and then insert the dowel as far as it will go. You can also drive it in with a hammer - but the impact force must be dosed well with plastic dowels so that the end does not deform. Then hold the hole in the component in front of the dowel hole and screw in the screw.

With this type of installation, which is possible with special frame or push-through dowels, the hole is drilled directly into the wall through the hole in the component. Then you insert the dowel through the component into the hole and completely screw in the pre-assembled screw. Push-through installation is particularly quick and is suitable, for example, for large shelves or other components that can no longer be moved without great effort after installation.

So funktioniert die Durchsteckmontagge
So funktioniert die Durchsteckmontagge

The push-through installation is particularly recommended for series assembly because it is not very expensive.

Photo: DAS HAUS / Kirchner

If a component is not supposed to lie directly on the wall - for example a trellis for climbing plants - the so-called spaced installation is used. The easiest way to achieve this is with brass dowels with a metric internal thread and correspondingly long metal screws or eyelets with lock nuts. They ensure that the component is fixed in a pressure-resistant and tensile manner at the exact distance from the wall. If plastic expansion anchors and classic wood screws are used, you can also use suitable spacer sleeves instead - these must be larger in diameter than the drill hole or be provided with a washer so that they are not pressed into the drill hole when the component is screwed on.

Which dowel is the right one?

Which dowel is best suited mainly depends on the surface, i.e. the wall to be drilled. But other factors are also essential to find the right dowel. You should ask yourself these questions:

  1. What material is the substrate made of?
  2. What do you want to assemble?

You will notice how soft the wall is when drilling: if you encounter great resistance, it is very hard and probably made of concrete. Smaller dowels and screws are then sufficient.

If, on the other hand, you only need to apply a small amount of force when drilling, the surface is soft, so that longer dowels with suitable screws lead to a good result.

You can also tell from the material of the wall by the color of the drilling dust:

  • White dust in soft masonry indicates plasterboard
  • Red drilling dust z. T. with black parts on brick
  • Gray dust on concrete
  • White, granular sand on sand-lime brick or aerated concrete - the latter, however, is much easier to pierce

Important: Before drilling, use a line finder to check whether power and water lines run through the masonry.

Once you have clarified what material the surface is made of, the choice of dowel also depends on what you want to attach. As a rule of thumb for dowels: the heavier the object to be hung and the softer and more perforated the wall, the longer and thicker you choose the dowels and screws.

Even smaller dowels hold heavy loads in solid material without any problems. In soft gas concrete, on the other hand, you need large, winged special dowels. To press soft insulation materials flat against the wall, dowels with a plate-like head are suitable. Distance dowels keep ventilated facade panels at a distance.

What load can the dowel hold?

How big the load that a single dowel can hold is indicated on the packaging. You should definitely pay attention to these values, otherwise a firm hold cannot be guaranteed even in the hardest concrete. If the object you want to attach is heavier, you should either use a different dowel or spread the weight over several dowels.

When choosing the dowel and the amount of dowel, you must also pay attention to the surface. As already mentioned above, a larger dowel is required for a softer surface, a smaller one may be sufficient for a harder one.

If you use several dowels, it is important to keep a certain distance between the drill holes so as not to damage the masonry. As a rule of thumb, a distance of approximately four times the length of the dowel applies.

Which screw fits the dowel?

In hardware stores, dowels are often already sold with the right screws. But even if the dowels were bought individually, it is not rocket science to find the right screws. Three things are essential:

  1. The screw length
  2. The screw diameter
  3. The type of screw
Schrauben und Dübel
Schrauben und Dübel

In our guide you will learn how to find the right screws for your dowels in the hardware store.

Photo: iStock / pedrosala

The optimal length of the screw can be easily determined: It should be as long as the dowel (with push-through installation plus the thickness of the object to be attached) plus the screw diameter. So if you have a dowel five centimeters long and a screw with a diameter of four millimeters and want to use it to screw a two centimeter thick board to the wall, the screw should ideally be 7.4 centimeters long so that everything sits securely in the end.

The screw that perfectly matches the dowel has a slightly smaller diameter than the dowel, because if it is too thick, it can grate the dowel in the wall. A firm hold is not possible. A dowel with a diameter of eight millimeters usually fits a screw with a diameter of six millimeters. However, there is usually information on the dowel packaging for this as well.

As a rule, common wood or universal screws are suitable for the most common dowels. However, you should not use screws with a drill tip for easier screwing into wood, as these can drill through the end of the dowel and possibly damage it so that it no longer holds properly in the wall.

If the dowel has a thread, the screw must fit perfectly. Metal anchors such as brass anchors are a typical example. Only a metric screw fits here (a so-called machine screw or lock screw). The nail plug cannot be used with a normal screw either. A nail screw is necessary here.

Drill dowel holes correctly

The basis for a securely seated dowel is a cleanly drilled hole in the ground into which the dowel is to be inserted. You should therefore work very precisely when drilling. How to get an exact borehole in which a dowel can later do all the work:

  1. The correct size of the borehole

    Choose a drill that matches the size of the dowel. If you want to use a 6-pin, you have to drill a 6-hole.

  2. Position the drill correctly

    Hold the drill against the wall as precisely as possible at a 90-degree angle and drill a hole that corresponds to the length of the dowel. If necessary, make a mark on the drill if you are unsure about the length. Never drill too deep, otherwise the dowel will disappear into the hole.

  3. Clean the borehole

    Then remove the dust from the borehole by either using a blower, using a vacuum cleaner or blowing hard with a straw - but be careful: you should keep your eyes closed!

Set the drill aside and then insert the correct dowel. It should now fit perfectly. If the borehole is too large - which is more common with porous old building walls - you can either use a larger dowel or press the intended dowel into the borehole with some filler. If the mass is completely dry, it should sit securely.

Bohrloch säubern
Bohrloch säubern

If the borehole is not clean, the dowel will not hold properly.

Photo: DAS HAUS / Kirchner

Dowel correctly: these are the most common problems

Even if you have followed all the tips, it can happen that a dowel does not hold as it should. But there are simple solutions to the most common problems.

Especially in soft walls or in those with cavities, it quickly happens that the drill slips, the drill hole gets too deep and the dowel disappears into it. Here some filler helps to fix the dowel in the right place. If you screw in the screw after it has dried out, the dowel is stuck without any problems.

If you don't have a filler at hand, you can also use plaster bandages to hold the dowel in the wall. Simply immerse the plaster bandage in water, wrap it around the dowel and insert it into the borehole.

If you have already inserted the dowel into the hole that is too large or too deep and can no longer get it out or it is stuck in the appropriate drill hole in the concrete, a trick helps: With a corkscrew, dowels of a certain size can be pulled out again very easily.

If the dowel rotates with the screw that is screwed in, the drill hole is either too large or it has not been cleaned properly, so that dust prevents a firm fit. If the dowel can be pulled out again, it should be replaced by a larger one. If it is not possible to pull it out, clamp small pieces of matches or toothpicks between the dowel and the borehole wall. As soon as you then screw in the screw, the dowel should find a hold.

If the dowel breaks out of the ground under load, you have used too few or too small dowels and screws. You can seal the hole in the wall with filler. If possible, choose another location on the wall for reassembly. If this is not possible, use larger or more dowels. You can put this directly into the still moist filler and load it after it has hardened thoroughly.

In the case of very soft or sandy walls, an acrylic paint can provide more strength. Larger objects with a considerable weight should then be fitted with chemical dowels or threaded rods.

Nadine Kleber

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