Dear AsktheChimneySweep,

My name is Rick and I’m from Illinois. After having my yearly chimney sweeping and inspection, the serviceman said that the chase cover had “rusted out” and needs to be replaced. I didn’t get a chance to ask him what this meant, he just left the invoice in the door with the recommended repair listed. I don’t even know what chimney chase covers are, is this is crucial fix? Money is short right now.



You wouldn’t know it but in the profession we see a lot of rusted out chase covers. My guys write estimates for replacing a chimney chase cover a few times a week. What the serviceman wrote on your invoice means that the chase cover, also known as the chase top, which actually covers the entire top of your chimney to keep out the elements and critters. It fits over the top of the chimney like a lid almost, and the chimney flue pipe extends up through the middle. What has likely happened in your situation is that the chimney chase cover, which is more often than not made of galvanized steel which is prone to rust, was allowing water to pool and as a result became rusted. This isn’t necessarily a pressing repair, but should be taken care of in a timely manner because the rust damage will continue to worsen until holes form and water penetrates the chimney’s flue.

Water damages almost all kinds of chimney covers including chimney caps and the chimney crowns. When it comes to caps or chase covers, I always recommend stainless steel. The extra cost of installing a stainless steel cap or chase cover over galvanized steel is completely worth the extended lifetime of the cap and additional reliability that you also receive. Rick, when you do decide to replace your chimney’s chase cover, elect for a stainless steel version. Although rust stain removal is not usually extremely difficult, the metal has already been weakened so replacement is definitely the best option.

Other times, rust problems are worsened by a poorly designed chimney chase. The chimney chase should be designed such that it sheds water from the chimney and does not allow it to pool. As a rule, if water is allowed to pool anywhere, whether it be on top of a chimney crown or on top of brick or anywhere else, a water problem will ensue. The chase should actually be constructed so that there is a little bit of a slope from the middle, where the chimney’s flue will stick out, down to the sides. This will allow water to run off of the top of the chimney and prevent premature rust problems.

Chimney chase covers come in different designs based on how many flue systems are being vented through your chimney. There are chase covers available with two or three holes for multiple flues and chases where the hole is off center for specially designed chimneys. There are many custom chase cover manufacturers who will design your chase cover to your exact dimensions. You want to make sure that you are taking accurate flue diameter measurements during this process as well.

Rick, as I said before, I would definitely not let this problem go for too long because rust stains are more than just unsightly, once water is able to enter the chimney you experience more problems will surely begin to occur. Make sure you are choosing a quality material and that the chase cover is sloped downward to prevent water from pooling.