Instruction for a sealed glass replacement
Instruction for a sealed glass replacement:
• Glaze above 4°C (40°F):
It is always good practise to glaze above 4°C (40°F). Below this temperature condensation and frost can contaminate the surfaces-interfere with adhesion. If you must glaze in cold temperatures, wipe all surfaces first, with solvent, such as xylol or MEK, then wipe dry.
• Form a watershed:
Gunnable sealants, when applied as a cap bead, should form a bevel or watershed away from the glass. When tape is used to the sightline, it should form a watershed when compressed. Do not undercut a sealant, compound or tape below the sightline. Minimum cap bead depth should be 4 mm (3/16 inch). Tool and finish sealant as required. Use tooling solution recommended by sealant manufacturer.
• Achieve Positive Contact:
When applying a heel bead, lap onto the glass a minimum of 4 mm, and make certain of positive contact with the sash.
When applying a toe bead, weather continuous or a corner seal, make certain it is large enough to contact both the glass and sash. Proper sequence is to install the sealant prior to the glass placement.
• Setting blocks:
Setting blocks used should be generally of Neoprene or EPDM with a Shore A hardness of 80-90 durometer. When used in combination with heel and toe beads, they should be first buttered with sealant, and then placed prior to installing glass. This ensures an uninterrupted seal between glass and sash member.
As a general rule, setting blocks should be centered at ¼ points. However, they can also be moved out to 1/8 points or to a point 15cm (6 inches) from the edge of the glass to the end of the setting block.
Setting block length should be 2.5 mm (0.1 inch) for each .09 square meters (square foot) of glass, but never less than 10 cm (4 inches). Setting block widths should be 2mm (1/16 inch) less than the full rabbet width and high enough to provide the recommended minimum edge clearance for the glass.
• Surface preparation:
Clean the sash surface and glass edge just prior to glazing, with xylox or MEK. Use clean, white cloths or lintless paper towels. DO NOT ALLOW SOLVENT TO AIR DRY WITHOUT WIPING. As work progresses, remove all excess sealant and smears.
• Avoid Glass Damage:
Glass should be carefully handled and glazed to avoid edge damage wich can occur when units are rotated or “pitched“ during positioning. One recommendation is the use of a rolling block to rotate the glass units. This minimizes possible corner damage by evenly distributing the glass weight along the edges, rather than at the corners.
• Shims and Spacers:
Shims and spacers should be used, generally made from Neoprene or EDPM, with a Shore A hardness as recommended by the appropriate glass manufacturer. They can be either individually inserted shims, or preferably, continuous rod or wedge. Porous materials such as polyethylene and polyurethane foam are not suitable as shims.
• Tape Compression:
Glazing tapes must be kept under proper compression. Depending upon the tape selected, this will vary from 10-50%.
• Air Seal:
When glazing a pressure-equalized system it is necessary to install an interior air seal, or vapor barrier around the perimeter of the glass unit. A heel bead of gunnable sealant accomplishes this best, since it readily bridges the space between the interior face of the glass unit and the sash. The air chamber created between the interior air seal and the exterior waterstop is vented to the exterior, thereby “pressure equalizing“ the air chamber.
Observe minimum face clearance, edge clearance and glass bite as recommended by the appropriate glass manufacturer. This allows the glass to freely float in the opening without undue restriction by the framing members.
• Vent Holes:
When glazing insulating and laminated glass, the sill member must be vented to the exterior. A minimum of 3 vents per sill, separated by the setting blocks, is recommended. Refer to the appropriate glass manufacturer for their recommended size and placement.
• Tape Installation:
When glazing insulating units: (1) provide an exterior long-life cushion and seal between the insulating unit and sash. (2) prevent water from in contact with the edge of the insulating unit-accomplished by incorporation vent holes in the sash design. (3) glazing sealants must be compatible with sealants used in the fabrication of the insulating glass assembly. Deviation from these rules may ultimately lead to insulating glass failure.
• Follow Manufacturer’s Specification:
Apply glazing materials according to the manufacturer’s specification. Use qualified mechanics who specialized in glazing and glass installation. Always report any satisfactory conditions, as soon as possible, to the general contractor for resolution be continuing.