Why Architectural Precast?

Architectural precast concrete offers many cost advantages over other cladding materials.

Precast is produced all year round in a controlled, cost-efficient production environment. Additionally it can be installed year round even in harsh winter conditions. This eliminates the need for costly winter weather protection and contributes significantly to compressing the overall building schedule.

Architectural precast can enclose the project quicker than any other cladding material. Typically, more than 100 square metres can be installed each day (10 panels per day at 10 square metres each). Precast’s installation speed can shave months from a construction schedule, thus reducing construction financing cost. Architectural precast is the cladding material of choice whenever superior aesthetics or construction economy is required.

Precast cladding combines the benefits of high durability, low maintenance, excellent fire resistance and energy efficiency. All precast is factory manufactured ensuring consistent quality.

The versatility provided by architectural precast is appropriate for use on high-rise office buildings, where the emphasis is on prestige and aesthetic appeal; low-rise industrial structures, where economy and durability are paramount. The true benefit of architectural precast is found in the virtually limitless architectural effects that can be achieved with its use.

Custom made forms are used to create precast panels in the exact size and shape utilising reveals, joint patterns and other architectural detailing specified by the designer.

Specific in-built colour effects can be achieved by using various oxides and/or exposed aggregates. Textures, which can be customised through the use of chemical retarders, acid washes and grit-blasting, can also provide light and shade to a plain concrete surface. Combinations of the above finishes can be realised within individual panels.

Post applied finishes such as paint, plaster or concrete stain are also popular in both commercial and residential precast projects.

Architectural precast cladding when combined with a properly designed joint is an effective barrier for both the infiltration of air and rain, and the exfiltration of air and moisture. The concrete panel itself will not permit the passage of water by the forces that cause it (ie. momentum of the raindrop, capillary attraction, gravity and air pressure). Although concrete provides a completely impervious outer skin, it is essential that these same forces be controlled at joints between precast components and precast and other interfacing building materials such as windows, curtainwalls, masonry, etc.

See Also: Delivery Parameters

Modified Rain Screen

Modified rain screen assemblies have been successfully used for many years. The back face of the precast joints are caulked tight, developing the air/vapour barrier and the exterior joints are caulked but allow for the exchange of air through the introduction of weep holes and breather openings. The result is an air chamber within the precast joint, vented to the outside. With air chamber pressure equalization to the exterior pressure, there is no force to drive rain into the joint.

Any moisture entering the joint will cling to the joint walls and then be drained out by the transverse seal. Insulation is applied to the back surface of the precast, along with an air vapour barrier and the finished interior surface which then completes the wall assembly.

Summary

Modification of the panel profile, panel edges, knowledgeable use of panel connectors, proper joint widths, and the correct use/application of sealant materials are all essential for the proper performance of a modified rain screen joint system.

Please contact Wilco, joint sealant supplier and professional precast sealant applicator who have proven expertise in the above applications, for more specific details, or for information about fire rated joint assemblies.