Historically, calcium lime was used for mortar rather than the dolomitic lime (calcium magnesium carbonate) most often used today. Properly done, repointing restores the visual and physical integrity of the masonry. With a low power (10 power) magnifying glass, examine the remaining sand and other materials such as lumps of lime or shell. Masons practice using lime putty mortar to repair historic marble. New mortar should match the unweathered interior portions of the historic mortar. 6 Dangers of Abrasive Cleaning It is the consultant's responsibility to determine the cause of the mortar deterioration and ensure that it is corrected before the masonry is repointed. 41 Seismic Rehabilitation 419-422. 31 Mothballing Analysis of unweathered portions of the historic mortar to which the new mortar will be matched can suggest appropriate mixes for the repointing mortar so that it will not damage the building because it is excessively strong or vapor impermeable. Using any of these power tools may also be more acceptable on hard stone, such as quartzite or granite, than on terra cotta with its glass-like glaze, or on soft brick or stone. The consultant must assist the owner in planning for logistical problems relating to research and construction. Analysis requires interpretation, and there are important factors which affect the condition and performance of the mortar that cannot be established through laboratory analysis. New construction "bloom" or efflorescence occasionally appears within the first few months of repointing and usually disappears through the normal process of weathering. 8 (August 1996), pp. Because some of the kinds of lime, as well as other components of mortar, that were used historically are no longer readily available, even when a conscious effort is made to replicate a "historic" mix, this may not be achievable due to the differences between modern and historic materials. Acceptable guidelines on particle size distribution may be found in ASTM C 144 (American Society for Testing and Materials). Although specifically intended for historic buildings, the guidance is appropriate for other masonry buildings as well. A quaternary ammonium salt obtained by formal methylation of the tertiary amino function of 4-diphenylacetoxy-N-methylpiperidine. Mortar components should be measured and mixed carefully to assure the uniformity of visual and physical characteristics. Ideally, repointing should be done in shade, away from strong sunlight in order to slow the drying process, especially during hot weather. A scoop of sand contains many small voids between the individual grains. For example, the new ASTM test method, ASTM C 1324-96 "Test Method for Examination and Analysis of Hardened Mortars" which was designed specifically for the analysis of modern lime-cement and masonry cement mortars, combines a complex series of wet chemical analyses with thin-section microscopy. 34 Composition Ornament Where existing mortar has been removed to a depth of greater than 1 inch, these deeper areas should be filled first, compacting the new mortar in several layers. A straight portland cement and sand mortar is extremely hard, resists the movement of water, shrinks upon setting, and undergoes relatively large thermal movements. September 1988. We will make sure you have the right damp proofing product to get the job done. Aesthetically, rising damp can peel, crack, and bubble paint and plaster work, create ‘water-tide’ marks that show where the water has risen to along walls, as well as efflorescence (a white salt deposit which also looks unsightly on walls, floors or ceilings). Specifying the appropriate ASTM mortar by proportion of ingredients, will ensure the desired physical properties. After tooling, excess mortar can be removed from the edge of the joint by brushing with a natural bristle or nylon brush. Unit pricing forces the contractor to determine in advance what the cost addition or reduction will be for work which varies from the scope of the base bid. If power tools are to be permitted, the contractor should establish a quality control program to account for worker fatigue and similar variables. Modern pigments are available which can be added to the mortar at the job site, but they should not exceed 10 per cent by weight of the portland cement in the mix, and carbon black should be limited to 2 per cent. Also when water rises it can deposit salt in building structures which causes corrosion and deterioration of integrity through a phenomenon known as salt attack. There should be a good handful of the material. endobj No definitive study has determined whether air-entraining additives should be used to resist frost action and enhance plasticity, but in areas of extreme exposure requiring high-strength mortars with lower permeability, air-entrainment of 10-16 percent may be desirable (see formula for "severe weather exposure" in Mortar Type and Mix). "Masonry Mortar." But, it should not be assumed, however, that white portland cement is always appropriate for all historic buildings, since the original mortar may have been mixed with grey cement. Brick Institute of America The decision to repoint is most often related to some obvious sign of deterioration, such as disintegrating mortar, cracks in mortar joints, loose bricks or stones, damp walls, or damaged plasterwork. Clearly, building managers will need to coordinate the repointing work with other events at the site. The DPC Cream and Fluid damp-proof course products can waterproof and saltproof a building by injecting them into a structures masonry. "Guide Specifications for Brick Masonry, Part V Mortar and Grout." /CreationDate (D:20180611033937+02'00') It was named after the stone from Portland in Dorset which it resembled when hard. In scheduling, seasonal aspects need to be considered first. Rising damp is an issue that has troubled builders and homeowners since Roman times. The mortar should be used within 30 minutes to 1Ω hours and it should not be retempered. Penetrating damp – chemical damp proofing products that include water repellents, damp proof paint for internal surfaces like walls and ceilings, and waterproofing membranes. 49 Historic Decorative Metal Ceilings and Walls 4 (July-August 1997), pp. Although manufactured sand is frequently more readily available, it is usually possible to locate a supply of rounded sand. Aesthetically, rising damp can peel, crack, and bubble paint and plaster work, create a water-tide marks that show where the water has risen to along walls, as well as efflorescence (a white salt deposit which also looks unsightly on walls, floors or ceilings). Thus, 30 per cent binder by volume generally should be used, unless the historic mortar had a different binder: aggregate ratio. 30 Clay Tile Roofs /Subject (Composition and properties of AZ\256 and TI photoresists) The use of antifreeze compounds is not recommended. It should also help develop sensitivity to the particular needs of historic masonry, and to assist historic building owners in working cooperatively with architects, architectural conservators and historic preservation consultants, and contractors. Recognizing this at the outset will help to prevent many jobs from becoming prohibitively expensive. Many laboratories that analyze historic mortars use a simple wet-chemical method called acid digestion, whereby a sample of the mortar is crushed and then mixed with a dilute acid. When the final layer of mortar is thumb-print hard, the joint should be tooled to match the historic joint. Unskilled repointing has negatively impacted the character of this late-19th century building. The ASTM designated them in decreasing order of approximate general strength as Type M (2,500 psi), Type S (1,800 psi), Type N (750 psi), Type O (350 psi) and Type K (75 psi). Replacement units should blend in with the full range of masonry units rather than a single brick or stone. Photo: NPS files. Any of these situations can give false readings to the visual or physical characteristics required for the new mortar. Typical signs of rising damp rather than other damp problems are a ‘tide line’ of yellowish or brownish staining or blown plaster in the lower area of your wall above your skirting board. 8B Reissued. For repointing, portland cement should conform to ASTM C 150. Vol. You must have JavaScript enabled in your browser to utilize the functionality of this website. This application may extend along the wall for several feet. 4-(2,2-Diphenylacetoxy)-1,1-dimethylpiperidinium, C[N+]1(CCC(CC1)OC(=O)C(c2ccccc2)c3ccccc3)C 43 Historic Structure Reports Staining the new mortar to achieve a better color match is generally not recommended, but it may be appropriate in some instances. 1 (January 1996), pp. 35 Architectural Investigation It is usually similar to the sand in the historic mortar and provides a better visual match. >>stream Pointing styles may also differ from one facade to another; front walls often received greater attention to mortar detailing than side and rear walls. If a source cannot be determined prior to the bidding process, the specifications should include an estimated price for the replacement materials with the final price based on the actual cost to the contractor. Methods for analyzing mortars can be divided into two broad categories: wet chemical and instrumental. The following other wikis use this file: Usage on en.wikipedia.org Nucleotide; Metadata. Selection of admixtures should be made by the architect or architectural conservator as part of the specifications, not something routinely added by the masons. 3 Improving Energy Efficiency 132-138. More recent, 20th-century mortar has used portland cement as a primary binding material. 4, No. Photo: John P. Speweik. Vol. Ferro, Maximillian L., AIA, RIBA. Masonry cement is a preblended mortar mix commonly found at hardware and home repair stores.

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