Masonry Magazine February 1982 Page. 32
SLOPE % IN. (3 mm) TO 12 IN. (300 mm)
CONCRETE OR STONE SILL
FLASHING
AND WEEPHOLES
SLOPE IN. (3 mm)
ΤΟ 12 IN. (300 mm)
CONCRETE
OR STONE SILL
(b)
2 FT. (600 mm) MIN.
(c)
EXPANSION
JOINT
FLASHING AND
WEEPHOLES
Concrete or Stone Sill
FIG. 6
Shelf angle supports, flashing should be provided in the wall. The function of flashing is to serve as a collector for any moisture penetrating the wall or the sill. It is important that the flashing extend through the brick to the exterior face of the wall at the lower end of the flashing and be turned down at least 4 in. (6 mm) to form a drip. The flashing at the sill should extend beyond the ends of the sill to the first head joint outside of the jamb of the opening, and should be turned up and outward for a distance of at least 1 in. (25 mm) at each end, see Fig. 5. If the ends are not turned up and out, the moisture collected on the flashing will have a path into the adjacent wall and there is no way to predict where it may go. The purpose of turning the flashing up and out is to assure that the moisture stays on the flashing until it drains from the wall. See Technical Notes 7A for a discussion of materials to be used as flashing.
Once moisture penetrating the wall or sill has been collected on the flashing, it must be removed from the wall. This is the function of weepholes. Weepholes may be installed in several ways, see Technical Notes 21C. Weepholes should be placed on top of the flashing, not one course up. If wick-type materials are employed, or if hidden flashing is used, the weepholes should have a maximum horizontal spacing of 16 in. (400 mm). If open weepholes with no wicks are used, the horizontal spacing may be increased to 24 in. (600 mm) maximum.
Drips. Every sill should be provided with a drip. The function of the drip is to prevent water from returning to the exterior face of the wall. The drip of a properly sloped brick sill is the lower corner of the brickwork. A drip in a concrete or stone sill is usually formed, or cut into the bottom face of the sill, as shown in Figs. 5 and 6. The drip on a concrete or stone sill can be cut in several shapes, Vee-shape, rectangular, semi-circular, or a combination of these. The shape of the drip is not important, but its presence and location are important.
The inner lip of the drip should be located a minimum of 1 in. (25 mm) from the exterior face of the wall, as shown in Fig. 5.
Connections. In brick masonry sills of short length, 4 ft. (1.2 m) or less, no special anchorage is necessary. However, sills of brick, concrete, metal and stone having long runs should be anchored to the masonry below or behind the sill, see Figs. 3 and 5. This will require penetration of the flashing below or behind the sill. Care must be taken to ensure that these penetrations are adequately sealed so that the flashing functions as intended.
Attachment of the sill to the window will vary with window type and manufacturer. It is most important that the joint where the sill and window make contact be sealed with a high-quality sealant, see Technical Notes 28 and 28B Revised.
Expansion Joints. When expansion joints are necessary, it may be desirable to install them in vertical alignment with window jamb lines. If this is done, the expansion joint should also be installed through the sill. This will enable the expansion joint to perform as intended.
If the sill extends beyond the jamb of the opening and an expansion joint is required at the jamb, then the expansion joint should be continuous around the entire sill extension, as should the flashing, see Fig. 6.
Construction
In the past, sills for use in brick masonry construction have generally been built in place, using conventional construction practices. A trend during recent years has been to use prefabricated sills, particularly when combined with a spandrel and soffit, see Technical Notes 40