Curtain Walls 101.3: Understanding Curtain Walls

Sometimes there are questions regarding curtain wall installation, and it is a good thing to understand because the ease of installation is another benefit of using fabric curtain walls over traditional construction. In fact, maintenance crews or those who are mechanically inclined can install a basic curtain wall system with relative ease. Also, installation usually takes hours or days, not weeks or months, and can be done cleanly with minimal interruption to daily operations. So let’s take an in-depth look at curtain wall installation.

Secure Mounting Angle, Then the Curtain Wall

The method used to attach the fabric curtain wall to the ceiling joists vary based on the wall’s position relative to the roof joists.

When the fabric curtain wall runs perpendicular to the roof joists, it is recommended that a two-piece curtain be used so that it is easier on the installer to field trim around the bar joists. In this situation, a mounting angle is stitch-welded or clamped to the bottom flange of the ceiling joists along the linear run of the wall location. The top of the fabric curtain wall panels are then attached to the downward flange of the mounting angle using self-tapping screws and fender washers on 15” centers.  This is the larger portion of the curtain and it suspends from the underside of the roof joists.

A second mounting angle is also clamped or tack-welded to the top flange of the joist to span between roof joists, just under the roof deck, and along the same linear run as the previous curtain. A smaller valance curtain is then secured to the mounting angle with self-tapping screws and fender washers so that the filler curtain overlaps the top of the larger bottom curtain below it. The result is a full height seal from floor to ceiling. Any field cuts around roof joists or other obstructions are sealed with special patch tape that chemically cures to the vinyl.

When the fabric curtain wall runs parallel to the roof joists, it consists of full height panels. A mounting angle is tack-welded or clamped along the top flange of the roof joists, just under the roof deck, along the linear run of the curtain wall. Each curtain wall panel is then fastened with self-tapping screws and fender washers. Again, special patch tape is used to seal field cuts around any obstructions.

Attaching the Curtain Wall to the Building

Whether the fabric wall runs perpendicular or parallel to the joists, the curtain easily attaches where it meets an existing building wall. A fabric-nailing flap matching the curtain material or a steel-mounting angle is used depending on the building wall type. Self-tapping screws or wall anchors secure the nailing flap or mounting angle to the permanent wall. The curtain is then attached to the nailing flap by Velcro connection or to the mounting angle by self-tapping screws and fender washers.

Additionally, a fabric sweep is added to the bottom of the curtain at the facility to form a bottom seal but is usually not anchored to the floor. The exception would be in cases of high negative or positive pressure. The sweep is attached to the curtain panel with Velcro and can easily be replaced if damaged or worn.

Installing Doors in a Curtain Wall

Similar to traditional construction, any type of door can be added to a fabric curtain wall as long as it is framed properly. Door frames vary in size and stature but the fabric curtain walls are attached the same regardless. Once the door frame is anchored to the floor, a rough cut is made in the curtain wall and the raw edges are sealed and pressed to the door frame with a plastic nail strip. Self-tapping screws and fender washers are used to secure the nail strip and curtain panel to the perimeter of the door frame.

Working around Obstructions

Fitting the fabric curtain wall around obstructions involves simple field cuts, which are then sealed with special tape mentioned earlier. One example is cutting around conduit pipes.  In that case, a single cut is made from the top of the curtain wall panel to the point where the conduit penetrates the panel. The fabric is fitted around the obstruction, the cut is resealed with the special tape, and then the curtain panel is fastened to the mounting angle. Making field cuts for obstructions and using patch tape to seal them is a very common practice and easy to do.

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