Benefits of Parapet Walls
A parapet belongs to a low wall built up over the roofline that normally extents around the boundary of a building. Parapets may be simply aesthetic or largely functional, like hiding mechanical equipment or functioning as a firewall.
The moisture may enter through the top portion of a parapet wall and it creates problems. To get rid of this issue, select a perfect cap.
There are different types of materials like limestone, terra cotta, hard-fired clay, or precast concrete to cap off the wall. These materials contain thermal properties identical to brick and concrete masonry.
Contrarily, metal includes a coefficient of thermal expansion almost three times higher than masonry that produces a considerable amount of differential movement among the parapet cap and the wall underneath. Metal versions should be arranged with firmly sealed slippage joints where the cap section bends.
Caps are available with various shapes, but they should contain pitch, projections (1-in. minimum), and incessant drips. These components safeguard the parapet from pooling water and resist moisture from flowing out of the exterior wall surface.
Most caps are prone to entering of moisture at the head (vertical) joints. In order to reduce penetration at these positions, rake out the mortar head joints, bed joints in the cap to a depth of ½ in., and use elastomeric sealant to fill the joint.
An incessant flashing membrane is to be installed directly underneath the mortar joint under the cap so that the moisture can’t penetrate through the top of the wall. This flashing membrane is built from sheet metal, combination sheet metal/asphaltic, or rubberized asphalt. The flashing has to be arranged entirely through the wall to make a slippage plane among the cap and the wall underneath. The cap should be anchored to the wall underneath.
Different types of stainless steel anchorage systems are applied to fix the coping to the wall. A flexible system should be set up so that the mason can be perfectly arranged with the dowel anchor through the pre-drilled holes in the cap. A considerate amount of mastic should be used to the flashing where anchor punctures may happen.
If the back portion of the parapet is fully uncovered, both exterior wythes should be built up of the same material. Brick situated on the backside of the parapet should be coated with rainproof water repellant.
The bottom flange of the steel beam should be connected with the concrete masonry underneath with a debonded shear anchor. The anchor is mechanically secured to the bottom of the beam at specified spacings that is arranged with the head joints in the concrete masonry wythe. A debonded shear anchor protects out-of-plane (but not in-plane) shear forces and allows structural movement of the steel beam (deflection). The anchor should be completely implanted in mortar, inside the head joint of the concrete masonry unit, for this connection to be effective.