Advice on fixings for concrete and cavities

Press, 31 August 1989, Page 29

Advice on fixings for concrete and cavities

by

HOUSE PROJECTS

RON BUTLER

A variety of fixings are available for concrete and cavities. General safety rules apply no matter which tools and materials you are using. Use safety goggles at all times. Use low speeds when you are using a masonry drill — between 400 and 600 R.P.M. Keep as far away from the edge as possible with any fixing. Concrete Drilling Masonry drills are available in a good range of sizes from 4mm to 20mm and in standard length (about 100 mm) and extra long (about 250 mm). They are tungsten carbide tipped and have a heated-treated shank and are suitable for use with both rotary and rotary percussion electric drills. Masonry drills can be used for drilling into concrete, blockwork, brick and glazed tiles. © Use with a rotary drill or a rotary/percussion drill. Recommended drill speed is 400 to 600 R.P.M.

© Use firm drilling pressure but do not push too hard. ® Withdraw drill at intervals to clear flutes.

© Use dry. Do not quench drill in oil or water.

Screw fixing to concrete Fibre plugs are made from highly compressed natural fibrous material which ensures a strong permanent fixing. They are tough and elastic so that the screw forms its own thread and expands the plug without damage. © Drill hole of compatible size to the plug into the masonry.

© Insert the screw one or two turns into the plug. © Using the screw, push the plug into the hole until it is just below the surface of the concrete.

© Turn the screw right into the plug to the end of the thread. © Withdraw the screw. As the fibre plug is now expanded it will form a secure fixing for the material.

© Place the fixture in position, re-enter the screw and turn until tight. Note that fibre plugs are not suitable for water immersion or wet areas. Nylon type fixings such as tapits are water resistant, waterproof and grip in solid or hollow core material. They are suitable for concrete, blockwork, brick through tin, hollow materials such as plaster board, Hardiflex and sheet laminated wallboards. Their uses include fixing shelving, heaters, lights, wall cladding and outdoor signs. The tapit comes with an integral nail which is hammered in but has a slotted head for removal if necessary. © Drill a hole the required diameter and depth through the fixture and into the masonry. © Insert the throughbolt through the fixture

into the hole in the concrete and tighten the nut. Caution — do not use these bolts too close to the edge of the concrete. Masonry nails are available in a variety of sizes. They are made from heat-tempered plated steel and are extremely tough. The point shape minimises timber and concrete damage and will also penetrate through steel. Typical applications are for concrete, brickwork and solid block work. Use for battering, fixing shuttering, bottom plates and other similar applications. Drive nails with a heavy hammer no less than 20mm into the concrete but no more than 40mm. Selecting a nail of the correct length is vital. Do not use in mortar joints or near the edge of the concrete.

© Drill hole required diameter through fixture and into substrate.

© Insert the tapit through the fixture until the head of the tapit is flush with the fixture.

0 Tap the nail in fully with a hammer.

“Through Bolts” or “Dyna-bolts” are some of the best known and versatile concrete fixings. "Through-bolts” can give extra strength to existing fixtures already in position.

Because you drill through the materials to be fixed, into the masonry, the need to marry up the two holes from material to masonry is obviated. Other advantages are rapid installation, variety of heads and sizes, corrosion resistance and substantial resistance to pull-out loads.

Cavity fixing Gravity and spring toggles are ideal fixings when you cannot fix into a wooden stud or dwang. Gravity toggles — for secure fixing in vertical cavities, gravity toggles offer a corrosion-resistant easy-fix method to gib board and laminated board. The off-centre bar pivots on a swivel nut with the toggle dropping automatically when passed through the hole. Spring toggles — these cavity fixings are activated by a spring which spreads the toggle when passed through the hole and can be used easily in ceilings and walls where other devices cannot be used.

More information about concrete and cavity fixing is available from Expandite N.Z., Ltd, Ramset Fasteners or Nuts, Bolts and Screws.