Product Description

Back-blocking is a mandatory fixing practice described in AS/NZS 2589:2007 Gypsum linings – Application and finishing. Back-Blocking Adhesive is a plaster-based setting type compound specially formulated for back-blocking ceiling joints or wall joints. Back-blocking reinforces plasterboard joints and minimises cracking and peaking that results from building movement.

Frequently Asked Questions

What the features and benefits of Back-Blocking Adhesive?

Long working time
Mixes easily to a creamy, lump-free gauge
Excellent wet tack
Excellent adhesion and water retention
Yellow pigmentation

What manufacturer recommendations are there for Back-Blocking Adhesive?

Knauf strongly recommends that Back-Blocking Adhesive is used to back-block all ceiling joints.
Back-Blocking Adhesive is designed to meet the requirements of AS/NZS 2589:2007 Gypsum linings – Application and finishing Section 4.4.4.2 for the fixing of butt and recessed joints.
Back-Blocking Adhesive may be used to install backblocks whilst fixing the ceiling plasterboard; alternatively it can be used to apply backblocks after the ceiling installation has been completed.
Back-Blocking Adhesive has a long working time to accommodate all work practices.

How should Back-Blocking Adhesive be installed?

Cut pieces of Knauf Plasterboard sheet to sizes no less than 200mm wide for recessed joints and 400mm wide for butt joints that will fit loosely between the framing members; the gap at each end must be no greater than 30mm
Apply back-blocking adhesive over the full face of the plasterboard pieces, using a notched spreader, to form beads of adhesive paste at right angles to the joint
Fix the next sheets immediately after the back-blocks are in place
Ensure all butt joints are raised, forming a recess, prior to back-blocking
Fix Knauf Plasterboard sheets horizontally to framing members, placing the back-blocks centrally along the full length of the sheet’s edge; ensure an overhang of at least 100mm for bonding to the next sheet
Alternatively, ceiling back-blocks may be cemented into position from above the ceiling after the sheets have been fixed and before they are flush jointed

What should be avoided when using Back-Blocking Adhesive?

Always back-block prior to setting the joints
Ensure Back-Blocking Adhesive has set and is completely dry prior to taping the joint
Back-blocking pieces should not be cut tight between the framing members
Avoid using on hot, windy days where there is the risk of early dry out
The inclusion of other materials to the mix will impair performance (e.g. reduced strength and poor adhesion) and void the product warranty

How should Back-Blocking Adhesive be mixed?

Always use clean cold water, tools and containers
Always add Back-Blocking Adhesive to water and mix to give a smooth paste (approximately 4kg of powder to 3L of water)
Mix only enough Back-Blocking Adhesive for approximately 120 minutes working time
Mix by hand or with a power mixer (max of 400rpm) until a workable paste has been achieved
Once setting has commenced the material cannot be remixed and must be discarded
Do not mix with residues of previously used compounds. Use of dirty tools or containers may reduce working time and strength

How should Back-Blocking Adhesive be stored?

Back-Blocking Adhesive should be stored under cover in a dry environment and protected from temperature extremes; storage in an unsuitable environment can shorten the life of this product.
It is recommended that Back-Blocking Adhesive is used before the best before date displayed on the bag It may still be usable after that date if stored unopened, in an appropriate environment.

You can order online to purchase in store or via invoice

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Knauf

Back-Blocking Adhesive

Applications

Specially formulated for back-blocking ceiling and wall joints
Plasterboard surfaces must be clean and dust-free
Ensure all joints are flush prior to back-blocking

Specifications

Additional information

Working Time	Setting type – Approx. 120 mins
Colour	White
Packaging	20kg bag
VOC	Less than 50g per litre

Downloads & Data Sheets:

Compounds and Adhesives Selector Chart

Compounds and Adhesives Catalogue

Back Blocking Adhesive Product Datasheet

Back Blocking Adhesive Safety Data Sheet

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