Capping Unused Chimney

If you are only talking a few feet of redundant flue then you ll probably be ok with fully capping after reducing the height with a single vent left in the blocked up fireplace.

Capping unused chimney.

The bottom is even easier. Unused though they can waste a lot of heat up the chimney. One old and virtually free method of capping off or sealing a chimney that is generally no longer used is to make a lead cap. One is an inflatable balloon type product that will seal the flue.

Single flue caps are the easiest to mount since they sit right on top of the flue. Put on heavy work gloves and use tin snips to cut a piece of sheet metal to the same measurements as the chimney opening. There are a few products you can purchase to block the chimney just above the damper. Slowly lower the cap onto the flue and push it down as far as it will go.

Align the open bottom of the cap with the top of your chimney flue. The key to capping the top of the chimney is to install a barrier that will be moisture and tamper resistant and will not be affected by environmental factors such as snow wind and sunlight. Even new cast iron dampers allow air loss. The rain cannot get in but it is not sealed air tight which does allow any inside moisture to slowly get out.

Usually unused chimneys are capped off with a bent sheet metal covering and perhaps a wire strap or weight on the top. These can simply be made out of a scrap or an offcut of lead beaten into the correct shape and bonded to the top of most chimney pots to effectively seal it and make it waterproof. Apply a bead of butyl rubber caulk around three sides of the chimney at. Spring loaded legs are fitted securely to the base of the cap which allow the cap to be securely fitted to the chimney pot.