Sometimes builders wish each other “soft walls” – without malice and purely as a joke. But weak structures are really capable of infuriating even seasoned installers, not to mention home craftsmen. With a lack of experience, not only the “sand” heterogeneous walls of old Soviet houses, but also modern building materials such as drywall, hollow brick, cellular concrete and the like, become problematic. In this article, we will tell you about the choice of the correct fasteners, the principles of reliable fastening in weak bases and share proven life hacks.
We put embedded elements in hollow structures in advance
Most often, this technique is used to create wall claddings, as well as frame partitions from metal profiles or wooden beams. In this case, the sheathing can be made of plasterboard, plywood, lining, etc. For example, you need to hang cabinets on a wall / partition, mount a washbasin, install a urinal or fix a boiler. To do this, in the right places, bars, pieces of plywood or boards are integrated into the frame. It will be possible to attach to these mortgages with ordinary wood hardware.
By the way, when decorating doorways in frame partitions, double wall profiles are used, and a wooden beam is also installed in them as a mortgage to stabilize the structure and for subsequent fastening of the door frame.
Molly drop-down anchors and butterfly dowels
Thanks to the “umbrella” that opens in the voids, both options have proved to be excellent for the installation of various objects on drywall. They can also be successfully applied to clapboard, plastics, plywood / OSB and other cladding.
The principle of operation of these fasteners is quite simple. We drill a hole with a drill, insert the fasteners, use the screw to crush and cock the legs, unscrew the screw and use it to fix the object on the wall.
For mollies and butterflies to work properly, nothing should prevent their legs from fully opening up. Therefore, for example, in a hollow brick, such fasteners are not always effective.
There is another option. It is conceived with the same meaning, but works in a slightly different way – this is an interesting fischer DUOTEC dowel .
Deformable polymer dowels
Now dozens of models of fasteners are produced, which, after screwing a self-tapping screw into it, radically changes its original shape in the wall. Special deformable zones can simply expand in the hollow material, not only to the sides (frame structure), but also, for example, in a spiral. Twisting variants of fasteners, which form a so-called “ball” in the deformable zone, deserve special attention.
By the way, they are universal, that is, they function equally well on both hollow and porous walls.
Recently, innovative two-piece universal plugs have emerged that work simultaneously by friction, folding and twisting.
When choosing a deformable dowel, like other types of fasteners, you need to “guess” with the length. The expanding part must go to the right place where it will work. You must have a clear idea of the structure of the wall, or you will have to act by the selection method.
Screw anchor plugs
In loose foundations such as aerated concrete, various kinds of dowels-screws show themselves quite well. They are made of plastic or metal, may have a drilling element at the end, or require pre-drilling before installation. These dowels have a pronounced rare thread, so when screwing in, they reliably cling to the porous material. In addition, after using a self-tapping screw, many models of plastic fasteners of this type also have a slight expanding effect on the base.
The Fischer GB frame dowel can be considered a type of screw fasteners (with some stretch, since it still requires hammering). Its longitudinal ribs, located in a spiral, cut rough threads and compact the material near them.
Self-tapping screws for wood in loose bases not made of wood
There is such a joking saying “a screw hammered in with a hammer holds better than a nail screwed in with a screwdriver.” And there is something in this. In fact, self-tapping screws – even without using any kind of dowel – often really help out the craftsmen, if necessary, to gain a foothold in porous walls. They hold well in aerated concrete, in gypsum boards and plasters, in shell rock blocks. Self-tapping screws are simply irreplaceable when mounting objects and brackets on adobe walls.
It is best to use wood screws with sparse threads. The longer the fastener you use, the better, as more turns will cling to the loose material. And the rod itself for self-tapping screws with a length of 90 mm will be thicker than, for example, 40 mm.
By the way, the idea of fastening with self-tapping screws in mineral bases has been supported by the developers of building systems for quite some time. An example is the so-called “turboprop” or “mechanical anchor”, “concrete screw”. They work simply. For a self-tapping screw with a diameter of 7.5 mm, a hole with a diameter of 6 mm is drilled with a drill, then with the help of a special bit – most often the “asterisk” T30 is used – the fasteners are screwed into concrete or solid brick.
Self-tapping screw for wood in drywall
If the embedded elements in the frame were not provided, and the existing profiles for fastening are not enough, in some cases screws can be dispensed with. For example, installers of stretch ceilings, when attaching the starting profile to a plasterboard wall, use wood screws with a length of 30–35 mm. Moreover, these do not have to be “black” phosphated screws, it will definitely not be worse if you use “yellow” screws.
Between the profiles – that is, only on the gypsum board wall plate – they are placed with a fairly “thick” step of about 7-12 centimeters, while screwed at an angle to the plane.
To prevent the screws from scrolling in drywall, it is necessary to set the screwdriver ratchet to the lowest possible values.
This is one of the most expensive types of fasteners in loose and hollow walls. They are usually used when mechanical options are powerless. Chemical anchor – also called “chemical dowel” or “injection mass” – is a two-component composition based on synthetic resins.
Using chemical anchors, bolts or threaded rods are literally glued into a porous or hollow base. By execution, they are of two types:
Single piece glass capsule / ampoule with a predetermined diameter, for example 10 or 12 mm. The capsule is placed in a pre-drilled hole, when the pin is installed, it breaks, and the separated liquids, mixing, solidify.
Double tube made of resin and hardener. A plastic perforated sleeve is placed in the dust-free hole. Then the resin mixed with the hardener is squeezed into it with a gun (this happens in the cartridge nose), and the pin is inserted. The mass adheres firmly to the threaded steel hardware and fills the voids near the fastener.
15 life hacks for reliable installation on weak bases
Drilling is better than hammering. Use a drill and carbide drill bit if possible. Or use the hammer drilling mode instead of the rotary hammer mode. This will make the hole tidier and the fasteners tighter.
In a loose wall, work with a smaller drill / drill. For example, if a 6 mm “quick installation” dowel will be used for fixing under the cork in a wall with weak brickwork, then use a 5 mm drill.
Do not use bent drills and drills, as they will “break” the hole in the base, making it larger than the nominal hole. For the same reason, the tool must be held confidently, firmly and evenly.
Drill Makita HP1640 + Hand screwdriver (with reverse) with bit D-58833
If the dowel is too loose in its place, then in addition to the standard nail, a self-tapping screw can also be screwed into the cork at an angle.
Instead of the standard plug-in element of the “quick installation” dowel, it is sometimes more reliable to use a self-tapping screw.
When working with a hammer drill in the workpiece, it is advisable to make holes in advance for the through passage of the fasteners. If you punch the workpiece directly with a drill and right at the place of fixation, then you can loosen the already installed fasteners.
Increase the number of used dowels and self-tapping screws, decrease the spacing of the hardware. According to this principle, “perforated” fasteners also work, in which quite a lot of holes are drilled for a large number of self-tapping screws.
For example, when you hang a TV mount on a weak wall, use all the standard holes on it.
By reducing the spacing of the fasteners, avoid placing the dowels and screws too close to each other, as well as from the edges. Otherwise, the effect of “grinding” or chips may appear.
Aim for the maximum contact area of the object to be installed with the base. The fact is that in most cases, fasteners work not only for separation, but also for shear. It is a good fit of the contacting surfaces that allows the required level of friction to be achieved.
Use combined fixing methods. For example, you can use “liquid nails” to help deal with shear forces, but use screws or dowels.
Install fasteners in a weak base slightly at an angle, this will achieve better resistance of the assembly to tearing loads.
Choose carefully not only the type of fasteners, but also pay attention to their length. At the same time, a long dowel is far from always better than a short one. For example, a frame dowel 40 mm long will hold well in the wall of the cinder block, and 60 or 80 mm can open in the voids of the building material and will not provide reliable installation.
Read the recommendations of the fastener manufacturers carefully. As a rule, the description indicates what bases they are intended for. For example, different models of Molly anchors are designed for different sheathing thicknesses.
Make it a rule to test fasteners for applicability in your environment by any means available.
If you already know that your walls are problematic, then prepare a more or less extensive assortment of fasteners. The fact is that in old houses, even the same wall can be assembled from different materials, and in different places there may be different physical characteristics.
If you have a lot of different fasteners at hand, and if you master different methods of fixing, only then will you be able to complete the task with high quality and without delay. Play it safe, test, experiment – there are no hopeless situations.