Anchor, threaded rod or plug: what holds
A fixing is chosen by two things: what the wall is and how many kilograms sit on one point. Four load classes, five substrates and our working options.
The load per point first
Divide the weight by the number of points and allow for leverage: a cabinet on two hangers is shear, a boiler on hooks is shear plus pull-out from the overhang, a railing is almost pure pull-out on the upper anchors. Four classes: light — up to 10 kg per point (skirting, cable trunking, a batten); medium — 10–50 kg (a shelf, curtain rail, kitchen cabinet, TV on a flat bracket); heavy — 50–200 kg (a boiler, air conditioner, cantilever); critical — railings, facade brackets, anything that moves and where a fall is dangerous. The “minimum pull-out” figure in a fixings catalogue is not a working load: divide it by three.
Concrete and solid brick
Light — SM-L 6×40 to 6×80 nail plugs, quick and cheap. Medium — Tchapai 6×50 to 8×80 expansion plugs or ZUM 6/8 with a screw: for an 80 kg kitchen cabinet, two hangers with two Tchapai 8×60 each give a 1.3× margin. Heavy — the TSX-500F frame anchor 10×(part thickness + 80): it holds up to 4.6 kN per point in concrete and 2.7 in brick; in bathrooms and outdoors only the “F” version with thermal-diffusion zinc, the plain TSX-500 only in dry rooms. Critical — a chemical anchor with an M10–M16 rod: the rods come from us, the resin, nuts and drill bit from the fixings supplier. Drill with hammer action; in brick not into a joint.
Hollow brick and clay block
Drill without hammer only. Light — SM-L 6×60; medium — Tchapai 8×80 or ZUM 6×52, but a cabinet over 60 kg goes on three points per hanger. Heavy — the TSX-500F holds only 0.8 kN here, too little for an 80 l boiler under the “three times the weight” rule: the right way is a chemical anchor with a mesh sleeve or a through-bolt with a plate on the far side. That is what we do: a boiler on a hollow wall goes on M12 through-rods with plates, the resin and sleeves are bought in.
Aerated and foam block
Ordinary expansion plugs hold 20–27 kg of pull-out in aerated concrete by the catalogue — after dividing by three that is nothing. The special ones work: RD 8×55 (shelf, curtain rail), RD 10×60 (kitchen cabinet, 4 per cabinet), RD 14×80 (50 l boiler, air conditioner). No hammer; RD 14 needs an Ø14 bit. An 80–100 l boiler and railings on aerated concrete — only a chemical anchor with a sleeve or through-fixing.
Plasterboard
On one 12.5 mm board the TNF “butterfly” and DRIVA hold 4–9 kg per point: a picture, a light, a light shelf. On two boards — Molly 9×65, up to 25 kg per point. A boiler, a kitchen or a TV on an extending bracket never hang on bare plasterboard with anything: an 18 mm plywood backing or a timber in the framing at the partition stage, then wood screws.
Railings and everything outdoors
Railing posts are designed for a horizontal load: at 1.2 m spacing and 1 m height the upper base anchors take 1.5–2.5 kN of tension. That is chemical-anchor territory with M10–M12 rods, four per post, no closer than 50 mm to the slab edge; plastic plugs are not used here. Outdoors the rods must be hot-dip galvanised or stainless — our galvanised grade 4.8 rods suit dry rooms and protected places; for a balcony buy stainless ones separately. We have the pump for blowing out holes; the bit and the resin come from the supplier.
In short
- Up to 10 kg — SM-L nail plug.
- 10–50 kg — Tchapai or ZUM with a screw; on aerated block RD 8/10.
- 50–200 kg — TSX-500F in concrete and solid brick; RD 14×80 in aerated block; in hollow brick a through-bolt or chemical anchor.
- Railings, facade brackets — chemical anchor with a rod, by calculation.
- Plasterboard — Molly up to 25 kg; anything heavy only through a backing.