I have had a sludge puddle up on top of my woodstove 3 times now I have also had smoke back up into house. The sludge smells horribly smoky and I am pretty certain that it is coming from the chimney I just don't know how or why?

Does your chimney have several bends, or does it go straight up?

Are there any T sections.

Sounds like a clog, and you may not have a cap.

Straight up, there is a cap, I recently ran a chimney sweep down and at least too the flue it seemed clean, however I have not checked from the woodstove up to the flue. I will do that today. Thank you

Remember your indoor flue sections are to be installed upside down so the larger female bell end faces up and the male end of the pipe fits in downward. In other words the crimped end of the pipe should face Down. This prevents any liquid/condensation from running down the outside of the pipe to the top of the stove. Usually the moisture will cook off and it will leave a sludge or hard deposit.

I agree with hvac1000. Also, I forget what it is called, but there is usually a cone shaped thing around the pipe, that prevents water, etc, from draining down the outside of the pipe. It is especially useful on flat roofs. Often knocking the pipe will loosen up any debris within it, be careful though, sometimes it all comes down at once and makes a bit of dust and smoke come out of the stove.

We used to burn this powder that would help prevent build up inside our pipe. We only had to clean it once or twice over a 5 year period.

One other thing, some flues have a few small holes in them... if it is possible, check to make sure those holes are open.