How do I use chemical anchor resin properly?

Chemical anchors are the strongest fixings available to a domestic user, and they are also the easiest to install badly, because a badly installed one looks and feels identical to a good one until it fails.

Safety

What you'll need

• resin cartridge and mixing nozzles
• applicator gun
• hole brush of the correct diameter
• blow pump or vacuum
• threaded studbar or anchor rods
• mesh sleeves for hollow substrate (optional)
• nitrile gloves

Step by step

1. Check the resin suits the substrate and the season.Cartridges state a minimum working temperature and whether they suit hollow, damp or cracked material. A resin used below its temperature range never reaches strength.
2. Drill the hole to the stated diameter and depth.The published load figures assume a specific hole size and embedment depth. Deeper is generally fine; shallower is not.
3. Brush the hole with the correct size brush.A brush that is too small does nothing. It must be a tight fit and reach the bottom.
4. Blow, brush, blow again.The standard sequence is blow twice, brush twice, blow twice. Dust left on the hole wall is the single most common cause of a resin anchor failing well below its rating.
5. Fit a fresh mixing nozzle.The resin and hardener only combine as they pass through the static mixer in the nozzle. A reused nozzle has cured resin in it and will not mix.
6. Waste the first part of the cartridge.Squeeze out until the extruded resin is a completely uniform colour with no streaks. Unmixed resin never cures and this is where it comes out.
7. Inject from the back of the hole forwards.Put the nozzle to the bottom and withdraw as you fill, so air is pushed out ahead of the resin rather than trapped behind it. Fill to roughly two thirds.
8. Insert the stud with a slow twisting push.Twisting distributes resin around the whole thread and works out air pockets. Resin should just weep from the mouth of the hole, which confirms it is full.
9. Use a sleeve in hollow material.In hollow or perforated block, a perforated mesh sleeve holds the resin at the anchor and lets it key through the perforations rather than running away into the voids.
10. Leave it strictly alone until fully cured.Do not adjust, tighten, load or even nudge it. The cartridge quotes a gel time and a much longer full cure time; use the second figure, and extend it when it is cold.
11. Tighten to the stated torque, not as hard as possible.The resin carries the load; the nut only holds the fitting against the wall. Overtightening can break the bond you have just made.

Tips

• Buy a brush that matches your hole diameter. The generic wire brush in the toolbox is not a substitute.
• In cold weather keep the cartridge somewhere warm before use — cold resin is difficult to extrude and cures very slowly.
• Set the anchor and mark it with tape so nobody leans on it or hangs a tool from it before it has cured.

Common mistakes

• Skipping the hole cleaning sequence — Resin bonds to the hole wall. If that wall is coated in drilling dust, the resin bonds to dust and the anchor can lose a very large fraction of its rated capacity.
• Not discarding the unmixed first extrusion — The first material through a new nozzle is not properly combined and will remain soft indefinitely, leaving the deepest part of the anchor unbonded.

If it doesn't work

Questions people ask