Unit 26

Sizes 7-5/8” high 15-5/8” long Common depths – 8”, 10”,12” 3/8” mortar joints Walls usually stand 7’-4”

Block Walls Series of blocks one layer over another is called a course Concrete blocks do not use forms Concrete block may be reinforced by pilasters Stack bond pattern is when one block is laid directly over another to produce a continuous vertical joint Stack bond requires reinforcement

Mortar Freezing weather affects mortar Low adhesion Less strength Failure in joints Coat of asphalt over mortar will ensure a dry basement Applying roofing felt over first coat will provide extra water-proofing

Mortar (continued) Mortar strength depends upon The rate which block absorbs moisture from mortar Plasticity or workability of mortar How much water the mortar retains Quality of workmanship by the mason Mortar will be usable for 2-1/2 hours at 80 degrees or higher Do not water down block before adding mortar Position the first blocks before applying mortar

Construction of concrete block walls Alignment of the first course is the most critical Lay the smaller holes of the block up to provide a larger mortar bed Check the blocks with a level or a straight edge Use a story pole to check if one course is 8” above the next Final gap in the wall is filled with a closure block “Thumbprint” hard will not leave an indentation and the mortar should be tooled Tooling should be done when the mortar has set

Control Joint Controls cracking due to stress Permits slight movement in a wall Gives the wall longer life Built vertically into a wall Should be plumb Should be caulked if it shows

Finishing Remove excess mortar from walls after it has dried Intersecting walls must be anchored Tops of windows and doors require lintels Total mixing time of fiberglass reinforced mortar should not exceed 5 minutes Use a joint guide when fiberglass mortar application is interrupted for more than 1 hour

Finishing (continued) Wet the wall prior to fiberglass mortar application Slope the finish grade away from the foundation for good surface drainage Backfill material should be expected to settle

Foundation information The same block is needed for reinforced mortar as is conventional mortar Split face block has one rough face that looks like stone There are many specialty blocks for specific purposes