How To Measure For A Chimney Cap

Here is how to measure a chimney cap.

Chimney caps are essential components of chimneys you may have to replace at some point.

Having a chimney cap repaired, installed, or replaced will require taking the chimney crown dimensions to ensure it fits perfectly. Because most homeowners will require some sort of guide, we’ve written this article to assist in that regard.

Standard Chimney Cap Measuring Guide

How do you measure for a chimney cap?

To correctly measure for a chimney cap, you’ll need to first identify your flue type. There are different types of flues each having its unique measurements.

In other words, the dimensions for one chimney flue cannot be replicated for another.

Before measurements are even performed, the flue type determines what chimney cap type to purchase. To better understand the topic under discussion, it is best we first discussed the different flue types.

This will be followed by how to measure for each type.

First off, there are two major categories of chimneys; masonry chimneys and factory-built round metal chimneys. Under each of these chimneys, categories are varying flue types and shapes.

i. Masonry Chimneys

The different flue types under masonry chimneys include the single-flue chimneys without extended flues and single-flue chimneys with extended flues.

Others are single-flue chimneys with flexible metal liners and multi-flue chimneys. Let’s take look at each type;

  • Single-Flue Chimneys without Extended Flues

As the name suggests, these chimneys do not have extended flues.

In other words, their flues are flush with the chimney crown. The chimney caps for such will either be top-mounted or standard single-flue chimney caps with brackets or legs.

  • Single-Flue Chimneys with Extended Flues

Unlike single-flue chimneys having no extended flues, the design here is different as it isn’t flush with the chimney crown but extended above it.

This is among the most common flue designs found on many properties.

Capping such chimneys is much easier as chimney caps are mostly attached or clamped on the flues.

  • Single-Flue Chimneys with Flexible Metal Liners

Some chimneys have flexible metal liners installed within the chimney structure. So, smoke from combustion follows the flexible metal tube and exits the chimney.

The most ideal cap to have installed on this type of chimney is the slip-in model.

  • Multi-Flue Chimneys

Some other chimney designs have multiple flues being housed in the chimney.

For these, the most appropriate chimney cap would be one that’s outside-mounted. It doesn’t matter whether the flues are flushed with the chimney crown or extended.

ii. Factory-Built Round Metal Chimneys

This chimney type is rightfully called so because it’s built-in a factory.

Like masonry chimneys, it also consists of different chimney designs.

They include single-wall metal chimneys, double-wall air-insulated chimneys, double-wall solid-pack insulated chimneys triple-wall air-insulated chimneys, and triple-wall solid-pack insulated chimneys.

Here, the manufacturer builds replacement parts for each chimney type. This includes the chimney caps. So, to have a cap installed on the chimney, dimensions will have to be taken.

Now, let’s provide you with measuring guidelines to follow for all chimney types.

  • Flue Shape Also Matters

We’ve added this to the two main chimney categories due to the importance shape plays in determining chimney cap measurements. Now, flues can be found in varying shapes ranging from oval, round, rectangular, or square.

Your flue shape will determine your chimney cap clearance requirements.

Taking Measurements: Masonry Chimneys

Taking measurements for masonry chimneys isn’t a complex procedure once you follow the guidelines provided here. Let’s discuss how to measure the different masonry chimney types mentioned earlier.

i. Measuring Single Flue Chimneys with Square or Rectangular Extended Flues

To measure for a chimney cap, you’ll need to take the length and width of the outside of the flue. With these dimensions, you’re able to search for a cap that fits perfectly.

ii. Measuring Single Flue Chimneys with Square or Rectangular Flues which Aren’t Extended

Phew!! Such a long description!

When faced with such scenarios, the type of measurements to be made will be determined by your choice of a chimney cap. That is models which are either top-mounted or single flue chimney caps with brackets or legs.

So, how do you go about measuring either type (top-mounted or caps with brackets or legs)? Let’s look at each type;

iii. Measurement for Top-Mounted Chimney Caps

If you wish to have a top-mounted chimney cap installed, you’ll need to measure your chimney’s entire length and width.

Also, measure the length and width of the area encompassing your flue, and lastly measure your flue’s height. Your cap must stand at a height of about five inches from your flue.

iv. Measurement for Chimney Caps with Brackets or Legs

For chimney caps with brackets or legs, the outside width and depth of your flue will need to be measured.

v. Measuring Single Flue Chimneys with Round Flues

For single-flue chimneys with round flues, you’ll need to decide what chimney cap to use.

Here, two types are available; those that fasten to the flue exterior and those that slip into the flue. Each type is measured differently.

vi. Measuring For Caps that Fasten to Flue Exterior

Measuring for caps that fasten to the flue exterior focuses on taking the outside diameter measurements of the flue.

vii. Measuring for Caps that Slip into Flue

For caps that slip into the flue, a measurement of the flue’s inside diameter is necessary. This should help you find a chimney cap that fits in perfectly.

viii. Measuring Single-Flue Chimneys with Flexible Metal Liners

Taking the dimensions for this time of chimney should focus on the inner diameter. This should be enough to find the right chimney cap that slips in.

ix. Measuring Single-Flue Chimneys with Oval Flues

This type of measurement like most is also determined by flue shape. Here, the focus is to measure the outside length and width of the flue. Dimensions were obtained with help with finding the right chimney cap.

x. Measuring Multi-Flue Chimneys

For multi-flue chimneys, the approach is quite different. Irrespective of whether the flues are extended or flushed with the chimney crown, you’ll need to measure the length and width of the chimney in addition to the length and width of the smallest area encompassing your flues. Also, the height of the tallest flue is necessary.

Taking Measurements: Factory-Built Chimneys

Factory-built chimneys come fitted with chimney caps. However, such caps could get missing or damaged.

You only need to determine the shape, the size as well as whether the cap was fastened to the flue exterior or was a slip-in cap. At this point, you’ll need to replicate the measurements as discussed under masonry chimneys.

These are detailed ways to measure a chimney cap.

The measurement methods aren’t complicated at all once you stick to this guideline.

Leave a Comment