Block Chimney Installation

Dig a hole 4 feet deep and 4 feet wide next to your foundation where you plan to install your chimney. Pour 6 inches of medium gravel into the hole and tamp firm. Build a level form in the hole 2 feet on a side and 10 inches high using ½ inch plywood and wooden stakes. Fill the form with concrete mix. Level the concrete and allow it to cure for a week.

Drill through your foundation to create an 8-inch hole for chimney cleanout access just above the chimney footing. Mix mortar. Cut an 8-inch section out of one side of a chimney block or use a precut cleanout block. Lay the block on a bed of mortar so the block opening lines up with the foundation opening. Coat the top of this block with mortar and lay an intact square chimney block on top of it. Repeat with the third block. Keep blocks plumb with your plumb level.

Install the precut cleanout flue tile into the first three blocks. Put a trowelful of mortar on the bottom and in each corner to keep the tile centered in the block. Install a metal cleanout door on the inside of the foundation. Secure the door in place with construction adhesive.

Insert two corrugated metal brick ties as you lay each level of block, starting with the block at grade level. Nail one end to the house wall and embed the other end in the chimney mortar. Install ties 8 inches apart. After every three blocks, check the chimney for plumb with a plumb line and install another section of flue tile with mortar. Stop when you reach a point about 2 feet below the first floor ceiling.

Set the precut heater flue access tile into the chimney block. Mark the house wall where it lines up with the hole in the tile. Remove the tile. Cut a hole in the house wall sized according to the size of your heater’s flue pipe and chimney thimble. Cut one or two chimney blocks to allow passage of the heater flue pipe into the chimney. Cement the precut heater flue access tile into the chimney. Resume laying chimney blocks and flue tile segments. Stop every 10 feet and wait 24 hours to allow the mortar to set.

At the roof eave, cut through the soffit, eave framing and roofing with the circular saw. Frame the opening if necessary. Take a 6-inch wide piece of metal flashing; slide 3 inches of metal flashing under the roofing, bend it down by 90 degrees and nail the other 3-inch end to the framing around the eave opening.

Build the chimney through the eave until you are above the roof line. Install outer flashing by bending a piece of metal flashing so the upper end fits about an inch into a mortar joint and the other end lays flat on the roof. Secure the top of the flashing by laying another block. Nail the bottom of the flashing to the roof and seal all joints with roof cement. Stop building when the chimney is 3 feet above the roof line. Install a stainless steel chimney cap according to manufacturer’s directions.

Coat the below-grade portion of the chimney with foundation sealer and backfill with dirt. Coat the above-ground portion with waterproofing paint. Caulk where the chimney joins the house siding and where it penetrates the roof eave.