Does Repointing Generally Include Repair

German masons repointing a wall in 1948.

Repointing is the process of renewing the pointing, which is the external part of mortar joints, in masonry construction. Over time, weathering and decay crusade voids in the joints betwixt masonry units, usually in bricks, allowing the undesirable entrance of h2o. Water entering through these voids tin cause significant impairment through frost weathering and from common salt dissolution and degradation. Repointing is likewise called pointing,^[1] or pointing up, although these terms more properly refer to the finishing step in new construction.

History [edit]

Traditionally, mortar was made with lime and sand, producing lime putty. In the early on 20th century, masons began using Portland cement, a strong, fast drying cement. Masonry cement made its advent in the 1930s, which is a combination of Portland cement and ground limestone.^[ii]

Repointing procedure [edit]

Examining the structure [edit]

Earlier starting whatever actual work, building owners examine the masonry units, mortar, and the techniques used in the original construction.^[2] They endeavor to place the true problem they are facing and discover out what were the causes of the deterioration or cracks. If in that location are cracks or problems in the bodily bricks or rock masonry there could exist a larger problem that too needs to be addressed. If there is a larger issue, repointing may cause further damage. If a historic structure needs repointing, building owners normally hire an architectural historian or conservator to help pinpoint the issues.^[2] If the crevice is smaller than 2mm and not causing any major defects, then it is better to get out it and not repoint.^[three] It is mutual to run across neat along old repairs because of the shrinkage of difficult mortar and the seasonal flexing along the articulation.^[3]

Establishing materials [edit]

Examining the structure before working will also help establish the strength and permeability of the original mortar in order to match the new. It helps to establish what the original components of the one-time mortar are in lodge to observe the best lucifer. Information technology is essential that the mortar used for repointing have similar functioning characteristics to the original mortar used in a edifice.^[2] Such performance characteristics include permeability, compressive strength, and coefficient of thermal expansion. The mortar must have greater vapor permeability and softer compressive strength than the original mortar.^[2] The mortar should as well not be stronger (in compressive strength) than the masonry units because it will non have give. Rather than the mortar relieving the stress, the masonry units will, which volition cause farther damage to the masonry unit, such as smashing or spalling.^[4] This is when the face or outer section of a masonry unit breaks away from the rest of the unit. This will exist more than expensive and strenuous to fix. And so for example, if a soft lime-based mortar was originally used, the virtually appropriate repointing mortar is likely to likewise contain a large amount of lime.^[4]

Restoration (earlier and after) of a Georgian brick facade in Composition, re-pointed in Irish Wigging, using hybrid lime mix mortar, later replacing damaged bricks with matching salvaged bricks

An architectural conservator can perform a mortar analysis in society to make recommendations for replacement mortar that is both physically and aesthetically uniform with the building. In that location are 2 common methods of analyzing mortar. The first is chosen "wet chemic." This is when a sample of the mortar is crushed and mixed with a dilute acrid. The mortar will be broken down, and the type of mortar and sand used will be determined past the color and the texture.^[2] Another form of "moisture chemical" analysis is the same process but the carbon dioxide gas that is given off by the digestion volition be collected and the type of mortar volition be determined by its volume. The amounts of each component volition likewise be determined. The 2nd method to analyzing mortar is "instrumental." There are several dissimilar forms of "instrumental" analysis; however, the most unremarkably used is sparse-department microscopy.^[2] This is when sparse slices of mortar are examined by a transmitted light microscope. This process can provide more information than "wet-chemical" examination. Other examples of "instrumental assay are scanning electron microscopy, X-ray diffraction, and atomic absorption spectroscopy.^[2] Analysis is non solely based on lab piece of work, all the same. There are important performances of mortar that can not be determined in a lab: original water content, charge per unit of curing, weather condition atmospheric condition during original structure, method of mixing and placing the mortar, and cleanliness of sand.

It is of import to as well match the colour of the mortar. However, in the by lime mortar tended to be mixed on site with any sand was locally bachelor. Since the sand influences the color of the lime mortar, colors of pointing mortar tin can vary dramatically from district to district.^[4] Weathering of the new mortar will also lucifer information technology to the old mortar.^[3] The tooling should also match the tooling of the historic mortar.

Test panels [edit]

Again, before starting whatever work, the methods and materials for the repointing volition exist practical in a examination panel. A test panel is an area on the structure out of plainly sight where the owner or conservator tin test the repointing methods they volition employ, the color of the mortar, and the skills of the mason.^[ii] This will likewise be good to determine the types of tools that should be used, which will exist discussed in the next paragraph. For a brick structure, the panel should not be any bigger than 3' x 3'. For other masonry units, the test console tin can be a piffling larger. It is also important to pick the correct flavor to exercise the repointing. Extremely high or depression temperatures can crusade rapid drying which can have negative effects on the mortar, masonry units, and the structure itself.^[ii]

Structure process [edit]

Removal of old mortar [edit]

After exam, the next footstep is cutting abroad the old mortar. The old mortar is removed to a depth equal to or slightly more than the width of the joint, or to the point where audio mortar is reached.^[2] Removal of old mortar between joints is done carefully to avoid harm to masonry units. On buildings with soft materials, such every bit under-fired brick, lime mortar, or terra cotta, removal by hand is oftentimes the most effective to avert damage.^[4] Hard Portland cement mortar is usually removed with a grinder or power round masonry bract, taking care non to harm the masonry units. Vertical joints or thin joints are done by hand or with small power chisels." If a power saw needs to be used, it'south but used on wide and uniform horizontal joints^[5] and in the middle of the articulation. A hammer and chisel are then used for the remainder of the mortar, closer to the masonry units.^[five] Caulking cutters with diamond blades are an acceptable ability tool to remove mortar in broad horizontal joints. They are ho-hum, have no rotation, and vibrate so they are likely to cause less damage to the masonry units.

Repointing the front façade of a rowhouse in Baltimore, Dr.

After the mortar has been cut out, the joints are vacuumed or brushed clean. After vacuuming, the remaining debris is removed with a water jet from the acme of the masonry surface area downwards.^[five]

Filling in new mortar [edit]

The areas with the deepest recession of mortar are filled outset. The mortar is placed in several layers, starting with the first layer of ane/4 inch.^[2] Information technology is hardened to a desired strength then another 1/4 inch layer is added. The process is continued until the mortar is flush with the masonry. High-lime mortar dries chop-chop, so after it reaches a particular forcefulness it needs to be sprayed with water to avoid chalking, poor adhesion, or poor durability. The structure is misted every two hours for ii days, then every four hours for two days.^[two] Information technology is important that the mortar stays wet for at least a couple of days while information technology is setting. The local atmospheric condition will control how long the structure should exist kept wet, nonetheless. Burlap or plastic is placed over the repointed wall or structure. This keeps the edifice damp and eliminates directly sunlight. The burlap and the plastic are not resting confronting the construction, withal. The burlap or plastic are anchored to the footing to avoid this.^[two]

There are different ways to lay the mortar joint close to the border of the brick. Some contractors bring the mortar to the very edge, affluent with the face up of the brick. Others get out it recessed dorsum to allow h2o to shed off the building. In that location are three types of recessed mortar: saucepan handle, weatherstruck, and simply recessed. The saucepan handle is when the mortar is in a curve shape away from the face of the brick. Weatherstruck is when the mortar starts close to the bottom brick and recesses back equally it goes upwards towards the upper brick. The tertiary, recessed, is when the mortar sits back from the face up of the brick. At that place is also tuckpointing, where a mortar of a contrasting colour is 'tucked' into the masonry joint.

If the color of the new mortar is still not similar to the old mortar after repointing and setting, the not-repointed areas of the structure can be cleaned. This may bring the colors closer together. To do this, a low pressure water jet is used to clean the onetime pointing. A high powered water jet is not to be used because this could harm the masonry and mortar.^[2] Chemicals are also non used with the water considering this could be harmful to the masonry or mortar. Nevertheless, if chemicals are used, the structure is rinsed afterward with fresh water and natural or nylon brushes. Another method to match the colors is to stain the new mortar. This is not recommended past professionals though, because information technology can exist harmful. If stain is used, the application is tested in the test console.^[two]

Run across also [edit]

Stonemasonry
Tuckpointing

References [edit]

^ "pointing, vbl. northward i. " def. 5 Oxford English language Lexicon 2nd Edition on CD-ROM (v. four.0) © Oxford Academy Press 2009
^ ^a ^b ^c ^d ^e ^f ^g ^h ⁱ ^j ^chiliad ^l ^k ^north ^o ^p Mack, Robert (1998). Preservation Briefs ii. Washington D.C.: National Park Service.
^ ^a ^b ^c Kingdom of the netherlands, Malcolm (2012). Applied Guide to Diagnosing Structural Move in Buildings. W Sussex UK: John Wiley and Sons, Incorporated. pp. 189–190.
^ ^a ^b ^c ^d "Lime Mortar : Haired and Unhaired Putty Lime Mortar". Mike Wye . Retrieved 2016-11-14 .
^ ^a ^b ^c Canada, Regime of Canada. National Research Council. "Structure Engineering Updates". nrc-cnrc.gc.ca . Retrieved 2017-11-30 .

External links [edit]

"Repointing (Tuckpointing) Brick Masonry". Masonry Advisory Council. Archived from the original on 2022-05-26.
Frew, Craig (2007). "Pointing with Lime". The Building Conservation Directory. Article on lime pointing repairs to historic masonry and brickwork.