We have a brick chimney on the side of our 110 year old, 2 story house. We aren't going to use the fireplace - we have a ventless insert we are going to use. The chimney leaks terribly. We are thinking about taking it down to just above roof level and stuccoing the rest of it, plus adding flashing to the sides where it joins the house. Is this a workable solution? We don't really want to remove the entire chimney - it "fits" with the age of our house.
Ventless gas fireplaces are a suspected health hazard, and may dealers won't sell them.
I strongly suggested a vented model, which will have two pipes: one for fresh air, one for exhaust. The new cap will likely solve your dripping problem:
If you have doubts about where the leak comes from, get a hose. Wet the chimney 1 meter above the ground and wait for the drip to stop. Repeat this until you get to the top of the chimney. I'll bet the leak is in your chimney cap, or whatever masonry topping the thing has.
you did not mention the location of the leak. The most common leak area is where the roof meets the side of the chimney. Go on the roof and take a look at the nature of the protection at that point. Normally, metal flashing and a waterproof material bridge from the roof to the chimney UNDER the finished roofing material (shingles, tiles, etc.), so a permanent long-term repair requires removal of the roofing material. Additionally, there is often a metal flashing several inches above the area where roof meets chimney. This simply acts as a little roof, deflecting water away from this area of frequent trouble.
So... For temporary DIY repair, get some good quality elastomeric type white crack sealer in a caulking gun cartridge and give a thorough seal to any cracks or gaps found in this area. Then use a thick white elastomeric roof repair material in a can like this stuff. Apply a thick coat and embed mesh reinforcing tape (you can use fiberglass mesh drywall tape) into it and apply another thick layer on top. Add coats until the mesh is covered.
The repair probably will not be pretty, and may not last forever, but it will help. below is a photo of a similar repair I did 3 years ago, still no leaks.