Masonry Essentials

What is Masonry?

Brick is the most common type of masonry although stone and concrete is also popular. Clay bricks, most of which have hollow cores, offer various possibilities in masonry construction, generally providing great compressive strength.

Solid brick masonry is made of two or more layers of bricks with the units running horizontally (called "stretcher" bricks) bound together with bricks running transverse to the wall (called "header" bricks). Each row of bricks is known as a course. The pattern of headers and stretchers employed gives rise to different bonds such as the common bond (with every sixth course composed of headers), the English bond, and the Flemish bond (with alternating stretcher and header bricks present on every course). There are no significant differences between most bonds, but the appearance of the finished wall is affected. Vertically staggered bonds tend to be somewhat stronger and less prone to major cracking than a non-staggered bond.

Proper care of masonry is important because broken or cracked bricks allow moisture to penetrate beyond the mortar which can lead to further rotting and degradation of structure. Proper care will increase the life of your structure reducing prohibitive reconstruction costs down the road.

Additionally, broken and cracked bricks are unappealing to look at and can give the impression of lack of general care to valuable property.

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The Advantages of Masonry

  • The use of materials such as brick and stone can increase the thermal mass of a building, giving increased comfort in the heat of summer and the cold of winter and can be ideal for passive solar applications.
  • Brick typically will not require painting and so can provide a structure with reduced life-cycle costs, although sealing appropriately will reduce potential spalling due to frost damage. Concrete block of the non-decorative variety generally is painted or stuccoed if exposed.
  • The appearance, especially when well crafted, can impart an impression of solidity and permanence.
  • Is very heat resistant and thus will provide good fire protection

Disadvantages

  • Extreme weather may cause degradation of the surface due to frost damage. This type of damage is common with certain types of brick, though relatively rare with concrete block. If non-concrete (clay-based) brick is to be used, care should be taken to select bricks suitable for the climate in question.
  • Masonry must be built upon a firm foundation (usually reinforced concrete) to avoid potential settling and cracking. If expansive soils (such as adobe clay) are present, this foundation may need to be quite elaborate and the services of a qualified structural engineer may be required.
  • The high weight increases structural requirements, especially in earthquake prone areas.

Structural Limitations

Masonry boasts an impressive compressive strength (vertical loads) but is much lower in tensile strength (twisting or stretching) unless reinforced. The tensile strength of masonry walls can be strengthened by thickening the wall, or by building masonry "piers" (vertical columns or ribs) at intervals. Where practical, steel reinforcement also can be introduced vertically and/or horizontally to greatly increase tensile strength, though this is most commonly done with poured walls.

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Tuckpointing

Tuckpointing is the art of repairing a mortar joint when mortar has degraded or become dislodged.  The term comes from the process of tucking mortar into the damaged mortar joint with the point of a trowel called a "pointing trowel." Tuckpointing is a critical maintenance task and keeps water from entering the brick wall cavity. If water is allowed to get past the mortar and into the wall, brick failure may occur such as cracking or spalling (popping off of the brick face).

It is different from "pointing" (to place plastic mortar into joints to correct defects or to completely fill joints in newly laid masonry) and "repointing" (to place plastic mortar into cut or raked joints to correct defective mortar joints in masonry).[1] The terms are often used interchangeably.

Mortar

The principal purpose of mortar is to adhesively bind together the individual masonry units. It also provides protection against the penetration of air and water through the joints in a masonry assembly.  Mortar also bonds the non-masonry elements of an assembly such as joint reinforcement and ties, as well as compensating for minor dimensional variations in the masonry units. Finally, mortar joints contribute to the architectural quality of the masonry assembly both through colour and shadow.

Ancient Egyptian mortars were made from burned gypsum and sand while later development in mortar technology utilized a combination of lime and sand. These mortars developed their strength slowly (through a process of carbonation). Since about 1900, Portland Cement has been incorporated into mortar to provide more rapid strength development.  Modern mortar is composed of cement and lime or masonry/mortar cements, masonry sand, water, and possibly some admixtures.

Mortars are supplied to the job site in three ways:

  • Site mixed – the mortar is prepared on site by the mason
  • Pre-mixed wet – the mortar is commercially prepared off-site and shipped in tubs ready to use. A retarder is added to the mixture to ensure the mortar in tubs does not set up before being placed in the wall.
  • Pre-mixed dry– the mortar is commercially prepared off-site. Water is added to the mix by the mason on site.

The supply of mortar is not typically specified but rather determined by the mason based on site conditions.

Masonry Upkeep

The following care should be taken to minimize the need for cleaning:

  • Adequate wall cappings to prevent water intrusion (and subsequent efflorescence bloom);
  • Caulking and flashings where required to effectively manage water movement;
  • Water repellent treatment to minimize absorption of rain borne contaminants, algae growth, and efflorescence, applied as soon as practical after cleaning.

Veneer masonry

Brick veneer construction has strength imparted by a framework of wood or a rough masonry wall of other material over which is placed a layer of bricks for weatherproofing and providing a finished appearance. The brick veneer wall is connected to the structural walls by "brick ties", metal strips that are attached to the structural wall as well as the mortar joints of the brick veneer wall. There typically is an air gap between the brick veneer wall and the structural wall. As clay brick is not completely waterproof, the structural wall has a water-resistant surface (usually tar paper) and weep holes are left at the base of the brick veneer wall to ventilate the air gap.

Most insulated buildings that utilize concrete block, brick, veneers or some combination thereof feature interior insulation in the form of fiberglass batts between wooden wall studs or rigid insulation boards covered with plaster or drywall. In most climates this insulation is much more effective on the exterior of the wall, allowing the building interior to take advantage of the aforementioned thermal mass of the masonry. This technique does, however, require some sort of weather-resistant exterior surface over the insulation and, consequently, is generally more expensive.

Dry set masonry

Dry set masonry supports a rustic log bridge, where it provides a well-drained support for the log (this will increase its service life).

Dry set masonry supports a rustic log bridge, where it provides a well-drained support for the log (this will increase its service life).

The strength of a masonry wall is not entirely dependent on the bond between the building material and the mortar; the friction between the interlocking blocks of masonry is often strong enough to provide a great deal of strength on its own. The blocks sometimes have grooves or other surface features added to enhance this interlocking, and some dry set masonry structures forego mortar all together.

Solid masonry

Solid masonry, without steel reinforcement, tends to have very limited applications in modern wall construction. While such walls can be quite economical and suitable in some applications, susceptibility to earthquakes and collapse is a major issue. Solid unreinforced masonry walls tend to be low and thick as a consequence.

Uniformity and rusticity

The selection of the brick used, especially for color, will affect the appearance of the final surface. In buildings built during the 1970's, a high degree of uniformity of brick and accuracy in masonry was typical. In later periods this style was thought to be too sterile, so attempts were made to emulate older, rougher work. Some brick surfaces are made to look particularly rustic by including "burnt" bricks, which have a darker color or an irregular shape. Others may use antique salvage bricks, or new bricks may be artificially aged by applying various surface treatments. The attempts at rusticity of the late 20th century have been carried forward by masons specializing in a free, artistic style, where the courses are intentionally not straight, instead weaving to form more organic impressions.

Serpentine masonry

A crinkle-crankle wall is a brick wall that follows a serpentine path, rather than a straight line. This type of wall is more resistant to toppling than a straight wall; so much so that it may be made of a single thickness of unreinforced brick and so despite its longer length may be more economical than a straight wall.

Stonework

Stone blocks used in masonry can be "dressed" or "rough." Stone masonry utilizing dressed stones is known as ashlar masonry, whereas masonry using irregularly shaped stones is known as rubble masonry. Both rubble and ashlar masonry can be laid in courses (rows of even height) through the careful selection or cutting of stones, but a great deal of stone masonry is uncoursed.

Natural stone veneers over CMU, cast-in-place, or tilt-up concrete walls are widely used to give the appearance of stone masonry.

Sometimes "river rock" (oval shaped smooth stones) is used as a veneer. This type of material is not favored for solid masonry as it requires a great amount of mortar and can lack intrinsic structural strength.

Growing in popularity among builders and homeowners are manufactured-stone veneers. The process is to sample natural stones from quarries around the world and recreate those stones using concrete, aggregate and colorfast pigments. To the casual observer there may be no visual difference between veneers of natural and manufactured stone.

Concrete block

Blocks of cinder concrete ("cinder blocks" or "breezeblocks"), ordinary concrete ("concrete blocks"), or hollow tile are generically known as Concrete Masonry Units (CMU)s. They usually are much larger than ordinary bricks and so are much faster to lay for a wall of a given size. Furthermore, cinder and concrete blocks have much lower water absorption rates than brick. They often are used as the structural core for veneered brick masonry, or are used alone for the walls of factories, garages and other "industrial" buildings where such appearance is acceptable or desirable. Such blocks often receive a stucco surface for decoration. Surface-bonding cement, which contains synthetic fibers for reinforcement, is sometimes used in this application and can impart extra strength to a block wall.

The primary structural advantage of concrete blocks in comparison to smaller clay-based bricks is that a CMU wall can be reinforced by filling the block voids with concrete with or without steel rebar. Generally, certain voids are designated for filling and reinforcement, particularly at corners, wall-ends, and openings while other voids are left empty. This increases wall strength and stability more economically than filling and reinforcing all voids. Another type of steel reinforcement, referred to as ladder-reinforcement, can also be embedded in horizontal mortar joints of concrete block walls. The introduction of steel reinforcement generally results in a CMU wall having much greater lateral and tensile strength than unreinforced walls.

Some concrete blocks are colored, and some employ a split face, a technique that results in two blocks being manufactured as one unit and later split into two. This gives the blocks a rough face replicating the appearance of natural, quarried stone, such as brownstone. Examples of splitface block - as well as other types of CMUs and brick - can be seen here. For applications such as roadway sound control walls, the patterns may be complex and even artistic.

Decorative CMUs have gained in popularity also, with units featuring a glazed, burnished or glossy finish emerging as innovative new options in interior veneers. Decorative CMUs most often appear in financial institutions, schools and other municipal or professional settings where an aesthetic-but-durable, or a virtually marbled product, is appropriate. Such blocks usually have a smooth finish and can have a visible internal aggregates, a solid uniformly colored glaze, or a visible aggregates protected by a clear sealant.

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Energy Conservation Tips

The Green Party of Canada offers extensive energy information on its website which home owners can use to upgrade home systems and effect lifestyle changes that reduce consumption and emissions.

David Chernushenko, a Green Party candidate for Ottawa Centre, offers Energy Tips that are easy to understand and implement. There is written information as well as video clips covering such topics as water efficiency, furnace tips, air conditioning, doors and windows to name just a few.

If you decide not to vote Green Party, at least you’ll feel good about being part of the solution!

http://www.greenparty.ca/page188.html

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