There is no easy way to do a chimney because if the mortar gets wet, it will run over the face of the bricks and make a mess, so the wet rag must be wrung out and carefully wiped across the face to remove any traces of mortar. Otherwise, when the mortar dries, it will appear as white splotches or streaks on the bricks no matter how well the bricks were laid, it will forever look bad. Once the mortar does dry out it’s almost impossible to clean it off without using an acid solution, which is not advisable on a slate roof due to the effect of the acid on the flashing. Take a little extra time to carefully clean twin brick when the job is done, before the mortar dries, and the chimney will he beautiful. You will need to remove any mortar or other debris that has fallen down the chimney when the top was rebuilt. Otherwise you risk plugging the chimney, and a plugged chimney is dangerous because it can allow carbon monoxide, an odorless and lethal gas, to accumulate in the house. If you have any doubts about whether your chimney’ is venting properly, call roofers Toronto and install a carbon monoxide detector in your home, available at most hardware stores.