Wall Tie Drilling Guide
Drilling
It is important to use the correct drilling technique when installing remedial ties to avoid excessive spalling of the affected material and to ensure the accuracy of each hole's diameter.
The drilling machine should be small (around 750w) and the operator should not lean or push heavily on the drill during operation as this will reduce the effectiveness of the hammer and increase the likelihood of spalling the back face of the brick. Rotary hammer drills holding SDS (Special Direct System) bits, used appropriately, will satisfy most common drilling requirements. However, when drilling into very soft masonry or hollow concrete blocks, rotary percussion drilling with 3-jaw-chuck type drills should be used. This may increase drilling time but will minimise spalling.
Health and safety
- Always locate, identify and isolate any electrical, water or gas services which may be present in the wall or the wall cavities and can pose a safety risk before drilling or cutting. Always take the necessary safety precautions. Use electrical safety gloves and wear appropriate footwear and eyewear.
Drilling into brick or mortar?
DryFix ties may be installed directly into the mortar bed in situations where drilling through the brick/block face is not acceptable. This will be satisfactory where the mortar is strong and in good condition. Angled drilling through the masonry may also be used in some circumstances. ResiTies or RetroTies may be used where the mortar is in poor condition and drilling through the brick face is not acceptable.
Drill types
Rotary hammer drills are designed to hold SDS drill bits and use a weight to create the impact force on the bits when drilling. The design enables efficient drilling into masonry, whether using large or small diameter drill bits. However, the direct hammer action also means that rotary hammer drills with SDS bits can contribute to excessive spalling when drilling into soft materials. In these situations a rotary percussion drill may be preferred.
Pictured: Dewalt SDS drill and SDS drill bit
Rotary percussion drills use a 3-jaw rotating chuck to clamp and rotate standard, straight-shanked drill bits. The hammer action of rotary percussion drills is provided by the rapid pulsing, backwards and forwards, of the chuck. The design does not provide the same efficient transfer of energy to the hammer action to that provided by the SDS. Accordingly, rotary percussion drills are not suited to the use of very large diameter drill bits. However, the gentler hammer action means that rotary percussion drills are well suited to drilling small diameter holes into and through soft masonry and concrete blockwork.
