How to Choose the Right Anchor — A Guide to the Differences Between Plugs and Anchors

How to Choose the Right Anchor — A Guide to the Differences Between Plugs and Anchors

Choosing an anchor is not a decision to leave to luck. An unsuitable anchor can break, tear out of the wall, or bring a hung item down — sometimes injuring people and property. The right choice rests on two main factors: the substrate and the planned load.

Anchor selectionHollow blockYtongGypsumCast concreteWedge anchorChemical anchoring

The two decisive factors in choosing an anchor

• The substrate (base material): the wall or surface where the connection is made — hollow block (black/Termodan), Ytong block (aerated concrete), gypsum board, or cast concrete. Each material has a different internal structure, and every anchor is designed to work correctly only in the substrate it was designed for.
• The planned load: the weight the anchor will carry, including an appropriate safety factor. Take dynamic loads into account too (vibrations, repeated opening and closing, wind), not just the item’s static weight.

How to identify the wall type before drilling

When you are not sure what the substrate is, a few simple checks on site can save expensive mistakes:

• Knock test: rap the wall with a thumb or the handle of a screwdriver. A sharp, hard sound usually means solid concrete; a hollow, dull sound means a hollow block; a relatively soft sound points to Ytong or gypsum.
• Drill test: drill briefly at low speed and check the drilling dust and the resistance. Concrete shows high resistance and uniform greyish dust; a hollow block suddenly “drops” into a cavity; Ytong drills relatively easily and produces light-white dust; gypsum drills with almost no resistance.
• Visual inspection: at the edges of openings, electrical sockets or wall corners you can sometimes see the exposed base material and get a clear indication of the material type and wall thickness.
• When in doubt: drill a small test hole in a hidden area, and on critical projects consult a professional or ADIT’s technical team before the final installation.

Quick summary table — wall type and recommended anchor

Black or Termodan block wall (hollow block)

Black and Termodan blocks are hollow, light concrete blocks, very common in Israel for external walls, internal partitions and the building envelope. The block has an internal structure of partitions and air cavities, with relatively thin outer walls (usually only 2–3 cm). Because of this, anchors based on large expansion inside the hole (such as the Jumbo anchor) lose their grip into the internal cavity and do not lock properly.

Universal plug — the recommended solution

A quality universal plug of 10 mm diameter, installed at a depth of 6–8 cm, can carry between 130 and 210 kg in pull-out. At a smaller diameter (8 mm) or a shorter depth, the capacity roughly halves. This type of plug works on the principle of peripheral grip against the block walls themselves, so it suits both hollow blocks and solid materials.

• Installation notes: do not use a plug that is too long (over 8 cm), as it may harm the capacity. Keep to a depth of 6–8 cm for the best result.
• Professional tip: drill in a black block without “hammer” mode (rotation only) so as not to weaken the block walls and prevent cracking around the hole.
• Quality: prefer plugs with a European standard. Poor-quality (“Chinese”) plugs usually hold 3 times less load, even if they look identical externally.
• Drill diameter: use a bit diameter matching the plug exactly (usually 10 mm for a 10 mm plug) — too wide a hole harms the peripheral grip.

Chemical anchoring in a black block

Chemical anchoring is a very strong solution, holding between 250 and 850 kg (usually around 350 kg). The load range is wide because failure usually comes from the block itself breaking rather than from the adhesive or the anchor.

Note: chemical installation in a block is more complex, requires skill and can be messy. Since it is easier and cheaper to install several universal plugs, chemical use in a black block is reserved mainly for edge cases — relatively high loads in a limited area, or a single connection that must carry a large load.

Ytong block wall (aerated concrete, AAC)

Ytong block (autoclaved aerated concrete, AAC) is a light, air-rich material — a mixture of cement, silica and a foaming agent that creates millions of tiny air bubbles. Unlike a hollow block, Ytong is solid throughout with no internal cavities, but the material itself is soft and less strong than ordinary concrete. As with a black block, the preferred solution here is a universal plug.

• Load: a standard 10 mm plug at 7 cm minimum depth will hold between 120 and 210 kg. Using a smaller-diameter (8 mm) or shorter anchor reduces the capacity by roughly half.
• Installation depth: unlike a black block, Ytong has no “maximum depth” — the material is uniform throughout its volume. Installing deeper than 10 cm will not harm, but also will not add significant strength.
• Installation tip: in weak Ytong, drill a hole 1 mm smaller than the plug diameter (for example a 9 mm bit for a 10 mm plug) to improve the peripheral grip in the soft material.
• Drilling speed: Ytong drills relatively easily with no need for hammer mode — drilling too aggressively can “chew” the soft material and enlarge the hole beyond what is needed.

Chemical anchoring in Ytong

Chemical anchoring is less recommended here. The difference in capacity versus a universal plug is negligible, and it requires very thorough cleaning of the hole and a dedicated adhesive suited to solid, porous materials. In most cases, a universal plug is simpler, faster and cheaper for the same result.

Gypsum wall

A gypsum wall is a non-load-bearing partition, made of gypsum boards (single or double) screwed to a framework of metal or timber profiles, with an empty air cavity inside. A gypsum wall is not intended for heavy loads — the connection strength is set mainly by the thickness and strength of the gypsum board itself, not by the anchor.

Locating the frame profiles behind the board

When a relatively heavy item must be hung, the strongest and safest solution is to connect directly to the metal profile or timber stud behind the board, not to the gypsum board alone. You can locate the profiles with a magnetic stud finder, a light tap on the wall (a “solid” sound versus a hollow one), or a visual check near corners and door frames, where vertical profiles are usually found.

Anchors to the gypsum board itself

Load capacity: anchors that open behind the board (such as a spring toggle or butterfly plug) can carry 60–90 kg (in double gypsum). Ordinary drywall screws, which do not open behind the board, hold only a few kilograms and suit mainly hanging pictures, light mirrors and tiny shelves.

Recommendation: do not hang cabinets or heavy furniture on gypsum without prior preparation. If you must, connect directly to the metal profiles or build an internal/external reinforcing structure (such as an internal timber board or an exposed support profile) that spreads the load over a wider area and not just onto the gypsum board.

Cast concrete

Cast concrete is a solid, dense material far stronger than block or gypsum, so the range of options available to you is significantly wider and the achievable loads are much higher. The right choice among the solutions depends on several questions: what type of load is required (tension, shear or both), whether the anchor needs to be removed and reinstalled, the permitted distance from the element edge, and the budget and time available on site.

Jumbo anchor

The Jumbo anchor is very common among amateurs, but in engineering terms it is usually the least good solution compared with others in concrete. Its expansion mechanism (a metal sleeve expanding around a plastic or metal cone) is not as uniform as a wedge anchor, so its performance depends heavily on the installation quality and the uniformity of the hole.

Nylon plug

A nylon plug is excellent for low loads. It is a plastic sleeve that expands around the thread when a screw is driven in, and suits hanging pictures, frames, light shelves and decorative items — a simple, cheap and fast solution to install.

Wedge anchor

The wedge anchor is the most cost-effective solution in terms of cost versus capacity. As the nut is tightened, an internal cone is drawn upward and pushes a splitting sleeve against the hole walls, creating a tight mechanical lock with a built-in pre-stress effect that suits connections requiring a tight clamp, such as base plates for steel structures, railings and industrial hanger shelves.

Caution: do not install close to the concrete edge, because the anchor exerts large pull-out forces during installation and may cause cracking. Important: insert the anchor up to the depth mark painted on it. A quality wedge anchor (12 mm) will hold 4–5 tonnes, while a simple anchor will hold less than half of that.

Concrete screw

A concrete screw is a screw driven directly into concrete, cutting an internal thread in the hole walls as it is driven — with no need for mechanical expansion.

• Advantages: very fast installation, can be removed and reinstalled, and allows work close to the concrete edge (unlike a wedge anchor).
• Disadvantages: less suitable for applications requiring a strong clamp of an uneven profile (such as railings), since it lacks the pre-stress tensioning effect of a wedge anchor.

Dynamic anchor

A dynamic anchor is an expensive anchor recommended in large diameters, in applications with a high shear demand where chemical anchoring is not wanted — for example, installing machines with vibrations, or systems that require a mechanical anchor approval (not bonding) for control and maintenance reasons.

Chemical anchoring (injection)

Chemical anchoring (injection) is the strongest solution for tension. It is based on mixing two components, and there are three mixing methods: manual, capsule and injection. Manual mixing is inefficient and weak (hard to keep an accurate ratio between the components), capsule mixing is expensive and cumbersome (limited in diameters and quantities), so professional work focuses on the injection method — a dual cartridge with a static mixer nozzle that ensures a consistent mix ratio in every batch.

Adhesive types for chemical anchoring — comparison table

Important note: installing chemical anchoring requires dedicated equipment (an injection gun, cleaning brushes, an air pump) and skill. If you have never worked with a chemical material, it is recommended to watch instructional videos before starting.

General comparison table — anchoring solutions in concrete

Safety rules and fundamentals in choosing and installing anchors

Beyond choosing the right anchor type for the substrate, there are several basic engineering principles to observe in every installation — regardless of the wall or anchor chosen:

• Safety factor: do not use the rated maximum load (capacity) as the actual design load. Apply a safety factor (usually in the range of 3–5, and even higher for items hung overhead or in public passage areas), according to the load type and the risk from a possible failure.
• Edge distance: installing too close to the concrete or block edge increases the risk of cracking and early failure, especially in expansion anchors (wedge, Jumbo, dynamic) that exert peripheral forces during installation.
• Spacing between anchors: anchors installed too close together, so that their “zone of influence” in the substrate overlaps, lose part of their combined capacity and may cause combined cracking.
• Cleaning the hole: in chemical anchoring, inadequate cleaning of the drilling dust dramatically reduces the bond strength. Blow and brush the hole per the manufacturer’s instructions (usually several repetitions of blowing and brushing) before injecting the adhesive.
• Accurate drill diameter: a deviation of even half a millimetre in the drill diameter can significantly harm the anchor’s capacity. Use bits of the diameter and quality recommended by the manufacturer, and replace worn bits.
• Pull-out test: on critical projects, at high loads or in an unknown substrate, it is recommended to carry out a pull-out test on site to verify the anchor’s performance in the specific conditions.
• Documentation and approvals: in structural work and safety systems (fire, railings, overhead hangs), prefer anchors with an official ETA/CE standard and full test certificates, and do not compromise on cheap quality (“Chinese anchors”) at critical loads.

Frequently asked questions about choosing an anchor

How do you know which anchor to use in a block wall?

For hollow block (black or Termodan) and for Ytong block, the recommended solution in most cases is a 10 mm universal plug. Avoid a Jumbo anchor in hollow block — it does not lock properly against the internal cavities. Chemical anchoring is a stronger alternative, but more involved and less economical for most applications.

What is the difference between a wedge anchor and a concrete screw?

A wedge anchor creates a mechanical lock with a pre-stress effect, which suits connections that need to be clamped tight, such as railings, but it is not suitable close to the edge of the concrete. A concrete screw installs faster, can be removed, and can be set much closer to an edge — but it is less suitable where the pre-stress effect is needed.

How long do you wait before loading a chemical anchor?

It depends on the adhesive. Polyester, acrylate and vinylester or hybrid adhesives reach initial cure in about 3 minutes and full cure, meaning full load, in about an hour and a half. Epoxy adhesives reach initial cure in about 20 minutes and full cure in about 12 hours. Do not apply the full design load before the final curing time has passed.

Can a concrete anchor be installed close to the edge of the element?

It depends on the anchor. Wedge and Jumbo anchors apply large expansion forces during installation and can crack the concrete if set too close to an edge. A concrete screw does not expand, so it allows work much closer to the edge.

What should you do if you are not sure what the wall is made of?

Use the knock test for the sound of the wall, a short drill test for the drilling resistance and the colour of the dust, and a visual check at corners and exposed openings. Where doubt remains, drill a test hole in a hidden area, and on critical projects consult a professional before the final installation.

How many anchors are needed to hang a shelf or a cabinet?

The basic rule is to divide the weight of the item, including the expected weight of its contents, between several anchors so that each one carries only a proportional share within its safety factor — never to rely on a single anchor for heavy or suspended items. A heavy cabinet or shelf usually needs at least two anchor points set well apart, and in many cases a connection to the profile or stud rather than to the plasterboard alone.

Can a cheap anchor hold as much as one to a European standard?

No. Poor-quality plugs and anchors typically hold about three times less load than anchors made to a European standard, even when they look identical from the outside. For critical loads and safety-related work, always prefer anchors with an official approval and test certificates.

What is the difference between chemical anchoring and a mechanical anchor?

A mechanical anchor creates an immediate lock by physically expanding inside the hole, and does not depend on curing time. Chemical anchoring creates a bond along the whole depth of the hole and generally allows higher tensile loads, particularly in large diameters, in cracked concrete or in low-quality concrete — but it needs curing time and dedicated equipment.

Can concrete anchors (wedge, Jumbo and so on) be used in a plasterboard wall?

No. Concrete anchors rely on expansion or bonding against a solid, strong material, and are not suitable for a thin, hollow plasterboard sheet. For plasterboard use anchors designed to open behind the board, such as a spring toggle or a butterfly plug — or better, fix directly into the metal profile behind the board.

Summary

Choosing the right anchor starts with an accurate identification of the wall or substrate type, and continues with matching the anchor to the planned load — including the safety factor, the distance from edges and the spacing between anchors. Once that basic choice is right, most of the problems seen on site — pull-out, items falling, weak grip — are prevented before they happen.

For a precise choice of the anchor suited to your project, or for engineering advice on complex cases and high loads, contact ADIT’s technical team or consult the detailed product pages for each anchor type.

Sources

• ADIT universal plug, wedge anchor, concrete screw, dynamic anchor and chemical anchoring (polyester / vinylester / epoxy) product data.
• General field guidance on substrate identification, anchor selection and installation safety (safety factor, edge distance, spacing, hole cleaning).