How to Lay a Chimney Block

Check the evenness of the chimney foundation area with a level. If you are building a chimney on the ground, the foundation is the ground. If you are building a grill or oven, then the foundation is the part of the grill or oven that the chimney rests on. If the foundation is not level, adjust it by resetting the blocks or removing dirt from the ground.

Put on work gloves and eye protection. Add cement mix, sand and water in a wheelbarrow in the ratios specified by the packaging instructions. Use a hoe to stir the ingredients to the consistency of smooth peanut butter.

Apply a 1-inch layer of mortar onto the foundation area for the chimney blocks with a masonry trowel. Set the first block on top of the mortar. Tap the block down with the trowel's handle into the mortar until the joint between it and the foundation area is 3/8-inch thick. Scrape away the excess mortar that squeezes out with the trowel.

Check the level of the block that you just laid. Do not allow the mortar to dry before ensuring that the block is perfectly level; otherwise, the entire chimney will be crooked and may even fall over.

Apply mortar to the joints between adjacent blocks. If you are using standard cement blocks instead of the type known specifically as chimney blocks, you will also need 3/8-inch of mortar between every two adjacent blocks in the same row. Chimney blocks, though, have large hollow spaces in the middle. Each one of them forms an entire course by itself.

Place each block so that it is offset from the block below it if you are using standard cement blocks to make the chimney. Each new cement block should straddle the joint between two existing blocks in the lower row. This will keep each joint supported and strengthen the entire chimney.