quambi house - Great Lakes Council

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3Figure 4: Penetrating damp in the kitchen can be traced to the roof drainage and possibly the flashing in the roof above it. The guttercan be seen to be blocked by tree debris and dampness in the wall from an unsealed parapet and, possibly, inadequate flashings is likelyto be contributing to the problem. The gutter needs to be fixed so as not to collect debris, the downpipe unblocked and the flashingsrepaired and possibly enhanced with a soaker flashing.Figure 5: Much misuse of cementmortar can be seen on the northern wall.Penetrating damp in the room behind thetop eastern corner is likely to be fromleaking of the downpipe or from the cementmortar or a combination of the two.Figure 6: Paving and stacked bricksbeside the wall will make the rising dampworse. The effective ground level should belowered as recommended in the technicalguide.2.1.2 SOURCES OF SALTSalt can build up in masonry from many sources as set out in the technical guide, “Salt attack and rising damp”published jointly by the heritage authorities of NSW, Victoria and South Australia and available from the NSWMay 2010Masonry damageCouncil–owned buildings in Stroud
4Heritage Branch of the Department of Planning (referred to as the “technical guide” below). The sources of salt mostlikely at Quambi House include airborne salts which build up over many years, garden fertilisers and, particularly, saltfrom Portland cement–based mortars used for brickwork repairs in recent years.2.1.3 FOUNDATION MOVEMENTSThere is evidence from the past repair of cracks in the brickwork that Quambi House has suffered minor foundationmovements in the past, particularly near the middle of the northern and southern walls. However, that cracking doesnot seem to have continued since the repairs and it is likely that the repair of the roof drainage disposal system hasrectified this problem.Unfortunately, the repairs to the brickwork using hard, impermeable mortar have led to moisture being forced insidethe building and damaging internal wall finishes. This is not a significant problem on the southern side which isprotected by a verandah, but the cement mortars have other disadvantages as described below.2.1.4 PENETRATING MOISTURESolid brick walls, which were the normal form of building construction before c.1890, rely on the mortar being morepermeable than the bricks and the walls’ ability to “breathe” to control moisture movements. The introduction ofimpermeable Portland cement–based mortars and “plastic” paints has reduced the evaporation of moisture from thewalls: when rain–driven moisture enters a wall it is often prevented from readily evaporating during the next dry periodand the moisture is forced further and further into the wall until it reaches the inside surface and appears behind thepaint, which is then damaged.When paints were based on lime (“lime wash”) the walls could still evaporate small amounts of moisture internallywithout damage: this no longer happens with modern paints, particularly with the build–up of multiple layers.2.2 The Old Courthouse2.2.1 GENERAL OBSERVATIONSThe old courthouse is a solid brick building from the mid–19 th century which has been damaged by both rising dampand penetrating damp. Much of the damage can be traced to the use of modern paint and mortar materials and to thepaving of the verandahs.2.2.2 RISING DAMP AND SALT DAMAGERising damp and attendant salt damage is principally affecting the front (western) wall, where a recently paved verandahhas bridged the damp proof course, and the use of plastic paints has reduced the ability of the wall to breathe: theresult is moisture damage on the inside of the building to both wall finishes and timber skirting boards. In Figure 7,a drawing taken from the technical guide is reproduced which shows an explanation of the problem and a possiblesolution.Figure 7: Illustration from “Salt attack and rising damp” illustratingthe common problem when concrete verandahs are placed and a possiblesolution. A cast iron grate can be installed level with the surface or,alternatively, ventilation can be provided by drilling beneath the pavingand ventilating it at the ends.Photos with descriptions of the damage are shown in Figures 8 to 12.Masonry damageCouncil–owned buildings in StroudMay 2010
Page 4 and 5: QUAMBI HOUSE AND OTHERS, STROUDR E
Page 8 and 9: 5Figure 8: Typical salt damage tobr
Page 10 and 11: 7Figure 13: Almost all the factors
Page 12: APPENDIX ARepair mortar specificati
Page 15 and 16: 2BatchingBatching will be undertake

quambi house - Great Lakes Council

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