Assessment of moisture related defects in masonry walls

Abstract

Moisture intrusion into walls continues to be one of the top challenges in the building construction industry in Uganda. The study assessed and investigated moisture related defects in masonry walls, materials and construction methods to mitigate moisture rise and related defects in masonry. This study made an assessment on moisture related defects in masonry walls, together with; carrying out a baseline survey on the building industry practice to find the cement to sand mix commonly used, and to assess prevalence of capillary water rise in buildings, determining the height of water rise by capillarity in masonry walls from damp proof course level, and finding out the materials and construction methods that can be used to mitigate moisture rise and related defects in masonry walls, as the specific objectives. Experimental masonry wall models measuring; 1.6m wide x 1.9m height x 230mm thick for the study. The models were built of ordinary clay bricks, well plastered and built with cement sand mortar / plaster of mix ratios; 1:1, 1:2, 1:3, & 1:4. Selected vertical points on the wall surface were cored and tested for moisture content. It was found that the masonry walls were susceptible to moisture rise, and it was also observed that; the stronger the mortar mix, the less the capillary rise of moisture in the wall. The height of water / dampness is highest at the bottom, just above the damp proof course levels, and moisture rise ranged between 0 – 0.6m above dpc levels. The study further investigated the efficiency of various water proofing materials that can be applied on the external walls to minimise capillary rise. The percentage reduction in moisture content was as follows; overlapping dpc 95, stone slates 94.1, glazed tiles 82.3, cement sand mortar in plaster with 4% clay giving 66.8, bituminous paint 44, facing bricks 43.7, and finally weep holes in plaster 30.5. All the three objectives were observed to be realistic, and true. And the study therefore concluded that water proofing treatment of masonry walls should be done to heights of not less than 0.70m above DPC level to improve durability of masonry walls against related effects. This provides knowledge, and innovation to the construction industry. And this study also recommends; the use of overlapping of damp proof course, together with slates, as some of the best water proofing materials. There is also need for conducting more research on the areas of; variation of strength of building units with moisture content, and failure mechanism of most water proofing materials.