Design For Dry Single Wythe Concrete Walls TB 0007B — Cracking
The proper application of crack control measures, including control joints, can help ensure satisfactory performance of the wall. These products may be covered by patents, or patents pending. It assures that water will not wick into the interior of the building. However, these materials generally are too dense for water to pass through quickly. If water enters the wall, it often can be traced to the masonry unit-mortar interface due to improperly filled joints or lack of bond between the unit and the mortar.
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When applying the sealer, if the whole job cannot be finished in one day then it is best to make the sections start and end at natural breaks in the structure and not in the middle of a large wall — just as one would do with any other coating or painting operation.
However, some limited secondary efflorescence may also be controlled. Concrete masonry units are manufactured blocks used in construction. After that, the concrete block is cured in an environment in which high humidity levels are maintained for at least 24 hours. Europe to see the durability of masonry construction. Their slow rate of heat discharge keeps interiors warm in winters, and their high rate of heat absorption makes for cool interiors in summers.
The split face texture offers a more rugged stone appearance and can add interest and dimension to an otherwise plain masonry wall. Half highs offer the same quality exterior finish as a cavity wall but with a shorter construction time. In ground face block, also known as burnished block, diamond grinding heads are applied to the face to expose the aggregates. Glazed block is ideal for clean rooms as well, as it does not allow collection of dust, germs, or bacteria. Lightweight units are made from expanded shale or clay, and are best for fire rating and thermal performance, because of air voids in the units.
The main objective is to keep water from penetrating or entering the wall in the first place. In a cavity wall are veneer, cavity, flashing and weeps, and backup. Consequently, the entire unit is treated so as to provide a back-up layer of protection that lasts the service life of the unit and protects it from moisture during construction.
Consequently, other moisture reduction methods such as flashing and control joints are critical to achieve full mitigation. However, post-applied water repellents are less successful in moisture prevention than integral repellents. While post-applied coatings can be a good surface repellent, they do nothing to prevent an untreated unit from getting wet prior to sealing. Water mostly moves downward—a principle that informs the locations for flashing on single wythe walls. For best results, mortar joints should be tooled to a concave profile. It is also important for water resistance that head and bed joints extend the full width of the face shells. Control joints, which are essentially vertical planes of weakness built into the wall to reduce restraint and allow longitudinal movement due to anticipated shrinkage, should be located where stress concentrations may occur.
Usually the analysis is implemented using free easy-to-use software. Essentially, openings and penetrations must be sealed and gasketed consistent with construction material and location specifics. There are no sills in masonry construction as the wall extends from the footing in a continuous assembly. As a matter of course, quality sealing and caulking are critical at the ceiling edge as well as at access to the attic and around all wall penetrations.
All excess mortar must be removed and any exposed masonry must be dry brushed prior to the end of each workday. The water flow should be at least four gallons per minute and fan nozzle should be at least 40 degrees. Download a printable version of this article. When using standard units for single-wythe walls, an application of portland cement plaster (stucco), paint, or opaque elastomeric coatings works well. Traditionally, through-wall flashing has been used to direct water away from the inside face of the wall and toward weep holes for drainage. Proper grouting effectively seals the vertical reinforcement penetrations of the flashing. The absence of reinforcement to provide doweling in plain masonry may be more of a concern, but loads tend to be relatively low in these applications.
A critical aspect of flashing is to insure that a buildup of mortar droppings does not clog the cells or weep holes.
TB 0007B — Cracking of Masonry Walls Technical Bulletin
Mortar nets at regular intervals or filling the cells with loose fill insulation, a few courses at a time as the wall is laid up, are effective in dispersing the droppings enough to prevent clogging.
An alternative is to leave out facing block at regular intervals just above the flashing until the wall is built to serve as cleanouts.
Solid grouted single-wythe walls, as are sometimes required, are not as susceptible to moisture penetration since voids and cavities where moisture can collect are absent.
Some regions of the country recess the bottom of the wall about an inch below the floor level to ensure drainage to the exterior.
Veneer and cavity walls (sometimes referred to as drainage walls) of course provide the most moisture resistance. Wall cracking provides an entry point for rainwater and moist air that may condense on the inside of the wall. Specification of a quality sealant for the control joints and proper installation is a must. Lower strength mortars exhibit better workability and can yield a better weather resistant seal at the mortar/unit interface. Head and bed joints need to be the full thickness of the faceshells for optimum watertightness. Wall thickness and dew points are also determining factors regarding vapor barriers. Acidic washes should not be used since they may reduce the water repelling properties of treated masonry. Keeping the masonry wall clean, as the construction progresses, using a brush and water minimizes cleaning efforts after the mortar has hardened. Require a qualified mason by documentation of experience with similar type projects. The tops of unfinished walls shall be covered at the end of each working day. The cover should extend two feet down both sides of the masonry and should be held securely in place. Once the water was placed on the unit, some of the water was absorbed, but there was still partial beading and standing water remaining on the unit.
I should just have a contractor stop by to do it for me. That shows me just how important it is to not only really on waterproofing to ensure that these units last. Traditionally, through-wall flashing has been used to direct water away from the inside wall face and toward weep holes for drainage. In this example, the termination angle prevents any water that collects on the flashing from penetrating to the interior, and the weeps and drip edge drain water to the exterior.
Proper grouting effectively seals around where the vertical reinforcement penetrates the flashing. Specialty units that facilitate drainage are also available from some manufacturers. However, fully cured units and adequate crack control measures are especially important to minimize cracks. Even though the shift is small ( 5 / 8 in. This shift therefore needs to be shown on the plans as shown here. If a bond beam or other obstruction requiring flashing is located in a high flexural zone, a structural analysis may be warranted with the reduced effective depth, d.
Cavity filter is any material used to prevent mortar droppings from clogging the weeps. Fully grouted concrete masonry walls do not require flashing. Control joints and/or horizontal reinforcement should be located and detailed on the plans to alleviate cracking due to thermal and shrinkage movements of the building.
Note that the location and vapor permeability of insulation can influence the condensation potential of a wall. Keeping the masonry wall clean as the construction progresses using a brush and water minimizes cleaning efforts after the mortar has hardened. Require a qualified mason by documentation of experience with similar type projects. The tops of unfinished walls shall be covered at the end of each work day. Always cover the siding after a day s work.
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