Masonry Defects - Summary

What Causes Defects? Structural movements from inadequate design, faulty construction or overloading. Ground movement. Defective materials. Chemical action (e.g. timber decay, sulphate attack) Moisture & thermal movements (e.g. clay expansion) Defects arising from conditions above ground. What to Check on a Leaning/Bulging Wall Check for loss of support to other elements. Check position & bonding of lateral restraints. Check if floors, roof & upper walls are contributing or restraining lateral movement. Check if it's a cavity or solid wall. Remedial Measures for Leaning/Bulging Walls Tie rods through floor or roof level to tie opposite walls together. Tie back floor joists and roof members to provide restraint and reduce SR (slenderness ratio). Key buttresses into a wall & carry them down to a stable base (requires adequate space) What Influences the Type of Measure Required for Crack Repairs? Width & extent of cracking. Internal & external wall. Type of mortar & strength of brick. Degree of seasonal fluctuation in crack width. What are the Remedial Measures for Cracks? Cutting out & rebonding/replacing cracked bricks. Raking out and repointing. Remedial Measures for the Failure of a Junction Between Structural Walls Stitch walls together with stainless steel ties. Use reinforced concrete corner ties. What are the Remedial Measures for the Failure of Built-in Timbers? Cut out rotten timber. Eradicate cause with treatment. Fill in cavities left with brickwork/concrete. Ensure lateral restraint of wall isn't jeopardised. Provide alternative means of support if required. What are the Remedial Measures for the Corrosion of Ferrous Metals? Remove corroded metal & fill cavity. If unable to remove, remove surrounding brickwork, clean metal & treat with rust inhibitor & try reduce moisture penetration.  What are the Remedial Measures for Corroded Wall Ties? Rebuild outer lead using non-ferrous or stainless steel ties. Drill for & fix corrosion resistant ties. Fill cavity with polyurethane foam. What is Sulphate Attack? The chemical breakdown of cement.  Signs: expanding/whitening of mortar joints, horizontal cracking, friable joints & increased height/length of wall. Remedial Measures: demolish & rebuild affected areas OR remove/protect from source of dampness. What are the Remedial Measures for Thermal & Moisture Movements? Establish cause of cracking. Insert movement joints at suitable positions. Use dry/mature bricks with sufficient movement joints to prevent damage in new buildings.  What is Efflorescence? Commonly occurs on surface of new bricks as they first dry out. Brushes off & normally disappears after two springs, if not, indicative or abnormal water penetration. Remedial Measures: check for defective dpc or rainwater goods & cut out and replace badly deteriorated bricks.  What is Frost Action? The formation of ice crystals within components already saturated with water during cold weather. Signs: spalling faces of bricks & disintegration of mortar.

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