Just when you think you have a handle on the different mounts of a ceiling fan, in comes the sloped ceiling. While this doesn’t change everything, you will probably find that it changes enough if you are trying to install a flush mount ceiling fan.

The problem with sloped ceilings is that your blades need to be kept clear of the wall and ceiling and need to be level so that the fan can function. Fundamentally, flush mount ceiling fans cannot be installed on a sloped ceiling without adaptation.

**Flush mount fans cannot be installed on sloped ceilings without adaption. A downrod and angled adapter mount are required, meaning the fan will no longer be mounted flush. The flush mount is designed to sit close to a flat ceiling and is unsafe to use at an angle.**

**Contents**show table of contents

## Flush Mount Fans Are Designed for Flat Ceilings

Flush mount (and hugger) fans are designed to address clearance issues with a lower ceiling by removing the downrod and attaching directly to the ceiling—sitting flush. People also often choose them for design reasons.

With the fan blades sitting closer to the ceiling boards, any sloping can interfere with their ability to rotate. You don’t want your paddles to hit or scrape along the ceiling whenever it is operating.

Additionally, having a ceiling crowding the blades will impact the airflow around the blades and the appliance’s efficiency.

## Flush Mount Ceiling Fan Can Be Adapted

Unless you have a hugger (or low profile) version, flush mount fans are usually designed for both standard downrod and flush installation (you can choose which installation you wish to use).

**So, you won’t be able to attach the fan flush to the sloped ceiling, but you can still use the ceiling fan you have; you will just need to switch to the downrod installation. **

This is only an option if you have the height for proper clearance. To install a flush mount fan on a ceiling with a slope (or pitch), you will have to add a longer downrod (extender/extension rod), which can be problematic if you have a flush mount to fit a lower ceiling.

**A lot of fans are equipped with the necessary hardware to accommodate angles up to 30° (approximately)**. This angle is a rough guide as some fans work with a range of angles between 28° and 34°, depending on the product.

If you are looking at an angle greater than what the hardware can handle, you will need an adapter. An adapter is actually an angled mount that replaces the canopy and can accommodate the different angles of a ceiling.

## The Maximum Degree of Slope

The way roofs are constructed, even vaulted or cathedral ceilings, means we don’t really get to the point of excessive sloping that would prevent installing a fan.

**As a standard, adapters can work with 45° angles. If the angle exceeds about 56°, you will likely need to have a custom adapter made. So, it depends more on whether the custom adapter can be secure and functional.**

You will have to work with a manufacturer based on the specific slope and height of your ceiling, as well as the dimensions of the fan you want to install.

So, what is the angle of slope of your ceiling? Do you need an adapter? While it does involve a little calculus, you can actually measure the slope of your ceiling quite easily.

### Calculate Your Slope

#### Measuring Values

You are going to need your ladder and tape measure for this part.

First, you need to measure the height of the floor to the ceiling at its highest point (height A) and its lowest point (height B). The difference between the two heights is referred to as the “rise”.

It might be helpful for the next step to mark the point on the floor where you are measuring height A. You can easily use a bit of tape.

Then, measure height B, which is the height of the wall, from the floor (in line with mark marked spot) to the point where the ceiling and wall meet.

Once you have established the two points of the rise, you also need to measure the “run”. This is the distance between the two points.

#### Calculating Values

For this part, you might want to get out your scientific calculator. We are going to be working with the Pythagorean theorem.

a ^{2} + b ^{2} = c ^{2}

However, for ease of use, we will flip it around to c^{2} = a^{2} + b^{2}. In this equation c = the slope (or the hypotenuse), a = the rise, and b = the run. Once we know the hypotenuse, we can find angle A, which is the pitch of the ceiling.

c = √( a ^{2}+ b ^{2} )

This will give you the hypotenuse, which we will now use to calculate sin A.

sin A = ^{a}/_{c}

Then you need to remove sin from the equation:

A = sin^{-1}( a ÷ c )

The value you get here is the angle of your slope. You must keep the decimal places as they are displayed for an accurate result. You can round up in the very last step for a more manageable number.

As an example, I will plug some values into the equation. Say we have a height A of 11 ft and a height B of 8 ft; this means our rise = 3 ft. And let’s say the run = 7 ft. Now we need to substitute these into the equation.

*c *^{2} = *a* ^{2} + *b* ^{2}

*c* ^{2} = 3 ^{2} + 7 ^{2}

*c* ^{2} = 9 + 49

*c *^{2} = 58

*c* = √58

*c* = 7.615773106

The hypotenuse (or length of the slope) is 7.62 ft. So now we need to solve for A.

sin *A* = ^{a}/_{c}

sin *A* = ^{3}/_{7.615773106}

sin *A* = 0.393919298

*A* = sin^{-1} (0.393919298)

*A* = 23.19

*A* = 23.19859048

*A* = 23.2

*slope of the ceiling* = 23.2°

## How to Adapt Flush Mount Fan for Sloped Ceilings?

### Step 1: Compatibility

Not all fans are compatible with adapters or are compatible with *all* adapters. The product information should supply you with this information.

### Step 2: Calculations

Calculate the slope of the ceiling and determine the adapter that will fit with the pitch of your ceiling.

*Don’t forget that you need at least 18” clearance between the fan blades and the wall.*

### Step 3: Purchase

Buy the appropriate adapter and downrod for your fan. This includes accounting for the adapter kit’s wet and dry (outside or inside) rating.

Some adapters, like the *Minka-Aire 45 Degree Slope Adapter Kit** _{(amazon link)}*, are not universal and are designed specifically for Minka fans.

Not all adapters are guaranteed to support a remote-control receiver because of the angle; however, you can find some that do. For example, one such adapter is the *Westinghouse Lighting 45-Degree Canopy Kit** _{(amazon link)}*.

### Step 4: Install

Replace the mount with a suitable angle adapter kit that will fit your ceiling fan model. Install the fan using the mounting kit and extender rod.

### How Long Should the Downrod Be?

The minimum length of the downrod will depend on the angle of your ceiling’s slope. However, you need an extended rod (about 12” at least) to provide the necessary space around the blades. Thankfully, we can estimate the downrod length you need.

4 + ( *radius* × ^{rise}/_{run} ) = *downrod length in inches*

You’ll find most fans’ diameter (half of which is the radius) in the product information. Then you just need your measurements of the rise and run.

We will use the same values as in the previous example. Assume we are looking at the *Honeywell Bonterra** _{(amazon link)}* for this example, as it is one of the models compatible with an angled mount. It has a diameter of 52” and a radius of 26″.

Now we can insert this into the equation with the other values.

4 + ( 26 × ^{3}/_{7} ) = *downrod length*

4 + ( 26 × 0.428571428 ) = *downrod length*

4 + 11.14285713 = *downrod length*

15.14285713 = *downrod length*

Here we can see that the downrod will need to be a minimum length of 15”. Now, the thing is that downrods come in a range that mainly increases by 6″ between options, meaning that you will need to buy an 18” downrod.

## Is It Safe to Use Flush Mount on Sloped Ceilings?

I don’t recommend attempting to use a flush mount fan as is on a sloped ceiling. It will likely damage your home and fan. Installing the fan flush to the angle can also be a safety risk. This means you have fan blades angled towards your head.

Using a flush mount fan on a sloped ceiling is also impractical. If you are looking at a flush mount because the ceiling is low, you will not be able to use the flush mount as adapting it will compromise the floor clearance, and without the downrod, it will hit the ceiling and not be able to rotate.

## Sources

https://www.1stoplighting.com/content/FAQinstallingfans/info.aspx

https://fandiego.com/when-to-use-flushmount-ceiling-fans

https://www.delmarfans.com/educate/basics/how-to-calculate-the-slope-of-a-ceiling/

https://www.universalfans.com.au/blog/fans-on-an-angle/

https://www.universalfans.com.au/how-to-calculate-your-ceiling-angle/

https://airflowacademy.com/downrod-length-for-sloped-vaulted-ceilings/