How to Measure for Replacement Skylight Domes & Diffusers

How to Measure for Replacement Skylight Domes

Understanding Skylight Dome Measurements

The replacement skylight dome size you need depends on the skylight flashing’s throat measurement (the skylight’s roof opening). This measurement ensures the new skylight cover properly fits and functions effectively.

Step-by-Step Measurement Guide

Step 1: Remove the Existing Dome

Carefully remove the existing dome from the flashing/skylight base.
Domes are usually secured with screws or pop rivets.
If necessary, use a screwdriver or drill to detach the dome.

Step 2: Measure the Dome Size

For Round Domes: Use a measuring tape to measure edge to edge across the diameter.
For Square or Rectangular Domes: Measure the edge-to-edge width and length.
Example: If your measurement is 420mm edge to edge, this is the dome size required.

Step 3: Measure the Skylight Throat (Nominal Size)

Run a measuring tape across the skylight opening at the roof level.
This is also known as the throat size or nominal size.
Example: If your skylight opening measures 400mm, this determines the required shaft size and the bottom ceiling insert size.
This measurement is essential if you are replacing additional parts such as shafts or diffusers.

Step 4: Confirm Measurements Before Ordering

All replacement skylight domes listed on our website use edge-to-edge measurements.
Ensure that your measurements match those available for order.
If uncertain, reach out to our support team with your measurements and images for guidance.

How to Know Which Replacement Skylight Diffusers You Require

Step 1: Identify the Diffuser Type

Determine whether your replacement diffuser is one of the following:

Flat model diffuser
Domed model diffuser
Vented diffuser model

Step 2: Measure the Diffuser Size

Use a measuring tape to measure across the diameter of the diffuser.
If the skylight diffuser is cracked or missing, measure the opening of the ceiling insert to estimate the required size.

Step 3: Identify the Material

Was the original diffuser made from frosted acrylic or prismatic material?
Choose a replacement that closely matches the existing material for optimal light diffusion.

Step 4: Check the Attachment Method

Does the diffuser twist and lock into place, or does it rest on the lip of the ceiling insert?
This determines compatibility with the existing skylight assembly.

Step 5: Consider Compatibility Issues

In some cases, your exact diffuser replacement may no longer be available due to discontinued skylight models or manufacturers going out of business.
If an exact match is unavailable, a different diffuser model or a full skylight ceiling insert upgrade may be required.

Important Notes for New Zealand & Australian Customers

NZ Standard Measurements: Some sizes may vary based on older skylight models, so double-check before purchasing.
AU Standard Measurements: Australian regulations may require compliance with specific roof profiles, so always verify throat size compatibility.
Material Options: Domes and diffusers are available in various materials such as acrylic, polycarbonate, and impact-resistant options. Choose based on your climate and durability needs.

This guide ensures a seamless replacement process and helps avoid incorrect orders. Always measure carefully to get the perfect fit for your skylight!