3.13 DOOR AND WINDOW BUCKS

Any lumber that might come in contact with concrete should be pressure treated or separated from concrete by waterproof material. (Be sure to check local code requirements.)

You can build bucks by ripping lumber to the same width as the wall. Or, 2 x 8,10,12 etc. and trim the openings later. Lintels should overlap the jambs, resting on top of them. The jambs will sit on 2x2’s and the sill will sit between the jambs. Starting with windows sizes, check to see how the manufacturers measures or produces the windows. Some 3040’s are 36x48, others chop a ½ inch off - which would be 35½ x 47½.

*LINTEL: Add 3 inches to the width of the windows rough opening size (to compensate for the lumber on either side – assuming the nominal thickness is 1½”) Lintels usually sit on jambs.

*JAMBS: Add 1½ inches to the height (for the thickness of one piece of lumber) of the rough opening. Cut two pieces to this size. Jambs usually sit on the 2 - 2x2’s with the sill on top, after it’s filled with concrete.

*WINDOW: Cut 2 - 2x2’s to the same length of the lintel. This allows for access to pour concrete below the window.

*SILL: Cut a single piece of lumber to the size of the rough opening width for the sill.

• Nail together with the top (lintel) over the two jambs
• Square the buck and attach vertical and horizontal braces to hold it square
• Set anchor bolts around each jamb to secure the buck to the concrete
• Countersink washer and nut
• Alternative - Nail #20 galvanized nails into the back sides to attach to concrete cavity.

Simplified: Add 1½” all the way around for wood bucks (assuming 1½” stock). Add an additional 1½” on the bottom (sill) for 2 – 2x2’s to create a channel to pour concrete below the opening. !!Be sure to add space for shims!!

Cross Bracing
Cross bracing is required on all windows and doors before placing concrete.

One option for bracing.

TIP: Be sure to add any extra rebar or stirrups around windows as required by plan/engineering.

TIP: Upon installation of the bucks leave a small ¼ inch gap between the top of the window buck and the bottom of the Greenblock Lintel course above – allowing for slight settlement while placing the concrete

TIP: Cut block as square as possible – it makes installation easier

One way to ensure nub alignment above a door is to lay block to the jam, bring the block around the outside of the door, and resume on the other side. Another method to ensure all the nubs line up is to lay out the entire 1st and 2nd course, cutting the door opening out afterwards. Then install the door bucks. (You may need to cut rebar if you use this method.)