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<br />Preservation <br /> <br />Recommended <br /> <br />Not Recommended <br /> <br />Building: Exterior Features <br /> <br />Masonry: Adobe, brick, stone, terra cotta, concrete, stucco, and mortar-- continued <br /> <br />Repointing only those mortar joints where there is <br />evidence of moisture problems or when sufficient <br />mortar is missing to allow water to stand in the mortar <br />joint. <br /> <br />Duplicating old mortar in composition, color, and <br />texture. <br /> <br />Repairing stucco with a stucco mixture that duplicates <br />the original as closely as possible in appearance and <br />texture. <br /> <br />Cleaning masonry only when necessary to halt <br />deterioration and always with the gentlest method <br />possible, such as low pressure water and soft natural <br />bristle brushes. * <br /> <br />Repairing or replacing, where necessary, deteriorated <br />material with new material that duplicates the old as <br />closely as possible. <br /> <br />Replacing missing architectural features, such as <br />cornices, brackets, railings, and shutters. <br /> <br />Retaining the extant or early color and texture of <br />masonry surfaces, wherever possible. Brick or stone <br />surfaces may have been painted or whitewashed for <br />practical and aestnetic reasons. <br /> <br />Repointing mortar joints that do not need repointing. <br />Using electric saws and hammers to remove mortar <br />can seriously damage the adjacent brick. <br /> <br />Repointing with mortar of high Portland cement <br />content, thus creating a bond that can often be <br />stronger than the building material. This can cause <br />deterioration as a result of the differing coefficient of <br />expansion and the differing porosity of the material <br />and the mortar. <br /> <br />Sandblasting, including dry and wet grit and other <br />abrasives, brick, or stone surfaces; this method of <br />cleaning erodes the surface of the material and <br />accelerates deterioration. Do not use chemical <br />cleaning products that would have an adverse <br />chemical reaction with the masonry materials, I.e., <br />acid on limestone or marble. <br /> <br />Applying new material, which is inappropriate or was <br />unavailable when the building was constructed. such <br />as artilicial brick siding, artificial cast stone, or brick <br />veneer. <br /> <br />Removing architectural features such as cornices, I <br />brackets, railings, shutters, window architraves, and' <br />doorway pediments. <br /> <br />Removing paint from masonry surfaces indiscrim- <br />inately. This may subject the building to damage and <br />may change its historical appearance. <br /> <br />*For more information consult Preservation Briefs: 1, "The Cleaning and Waterproof Coating of Masonry Buildings" and Preservation Briefs: <br />"Repointing Mortar Joints in Historic Brick Buildings." Both are available from Technical Preservation Services Division, Heritage ConservatiJ' <br />and Recreation Service, Washington, D.C. 20243. <br /> <br />20 <br />