11. Installation – flue connectors (b) fluing off the top into an existing masonry chimney. If you flue off the top of your stove into an existing chimney you will come up against the problem of how to make a watertight connection between the fluepipe and the chimney. "Watertight" because woodstoves always generate water vapour however dry your wood and there's a more than even chance that at some point in the burning-cycle condensation will occur somewhere in the stack. XXWhen that happens, water and the other distillates (creosotes & tars) percolate down to the bottom. And if they start to dribble down the hot, outer surface of an exposed fluepipe you'll be cursed with an acrid smell that catches the back of your throat. XXFor this reason, a flue serving a woodstove should be designed on the same principles as a tiled drain, since it's doing much the same job. The socket ends of all flue pipes must be kept to the TOP to catch and contain moisture XXAll joints must be sealed with fire cement. Fortafix adhesive fire cement is outstandingly suited to all work involving flue connections. XXIt is by no means easy to form an absolutely watertight seal between a metal fluepipe and a masonry chimney, since the two materials expand and contract at different rates when exposed to the extremely high temperatures they work at. XXThis is one more argument for fitting a multifuel flexible liner. By this means you eliminate the whole problem and plug a kit of components into each other right from the top of the chimney down onto the stove.

For information on a useful technique for connecting a metal fluepipe into a masonry chimney go forward to the next frame.