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9. A sealant lap joint may be dimensioned using the same procedures as for a butt joint.

10. There are many types of glazing details that include wet (gunnable) sealants. In general, these incorporate synthetic rubber spacers that regulate the depth and thickness of the sealant according to the principles laid out earlier. In the detail to the left in the drawing, the glass is set on synthetic rubber blocks and centered in the metal frame with the aid of compressible spacer strips that also serve as backer rods. This detail minimizes the number of different components needed to install the glass by eliminating any gaskets. The detail to the right uses a preformed synthetic rubber gasket on the interior side for easy installation and a neat appearance. The outside is sealed with a gunnable sealant for maximum security against leakage. Glazing details are usually developed by manufacturers of cladding and glazing systems rather than by detailers in architectural offices.

11. This is an example of a preformed synthetic rubber gasket used to close a movement joint in a high-traffic horizontal surface, such as a roadway or a parking garage. The gasket is slightly wider than the joint and must be compressed during installation. D>

9. Sealant Lap Joint

Installed

Stretched

Sealant

Sealant

10. Glazing Details Using Wet Sealants

Sealant

Sealant

Rubber gasket

Closed-cell sponge gasket

12. Preformed Gasket Glazing

Lockstrip in Place

Installation

Lockstrip

13. Lockstrip Gasket Glazing

Metal sheets

Tape sealant

14. Preshimmed Tape Sealant

12. Preformed gaskets are widely used to seal between window glass and metal framing. In this example, a closed-cell sponge gasket is inserted first; then the glass is inserted. Finally, a dense gasket in a roll-in wedge profile is forced between the inside face of the glass and the frame, compressing the sponge gasket and holding the entire assembly together. For additional security against water penetration, a bead of gunnable sealant is sometimes placed over the outside gasket. This is called a cap sealant.

13. There are many types of synthetic rubber lockstrip gaskets that are useful in glazing. This example incorporates a pine tree spline that is inserted into a slot in a concrete sill or jamb. The glass is installed in the gasket, and then the synthetic rubber lockstrip is inserted with a special tool to make the gasket rigid and lock the glass in place.

14. Preshimmed tape sealants arc made to be compressed between components of nonworking joints. The tape is thick and very sticky. The semirigid shim rod in the center of the tape controls the thickness of the joint and limits the tendency of the surrounding mastic to squeeze out.

Controlling Water Leakage: Sealant Joints and Gaskets

Controlling Water Leakage: Sealant Joints and Gaskets

15. The waterstop is a preformed synthetic rubber gasket used to seal pour joints and movement joints in concrete foundation walls. The example shown here features a center tube that allows the waterstop to stretch or compress considerably in response to movement in the concrete walls. Many other shapes of synthetic rubber waterstops are also manufactured, along with alternative designs made of rigid plastic, metal, mastic, even bentonite clay, which expands and seals when wetted.

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