Identify Your Skylight
Use our easy guides to identify domes, diffusers and more before ordering.
Skylight Dome
Sits on the roof
Product Identifier
Upload photos & sizes
Skylight Diffusers
Inside the room
| What Skylight Part Are You Replacing
Identify which part you need below, then confirm your size before ordering.
Skylight Dome (Roof)
The skylight dome is the outer cover installed on the roof. It is typically made from clear or opaque acrylic and sits over the skylight opening to allow natural light into the home while protecting the skylight from weather.
Over time replacement skylight domes can become brittle, discoloured or cracked due to sun exposure, hail or general ageing. In many cases the dome can be replaced without replacing the entire skylight unit, making it one of the most common skylight repairs.
Skylight Diffuser (Ceiling)
The skylight diffuser is the panel located in the ceiling that spreads natural light evenly into the room below. It sits at the bottom of the skylight shaft and helps soften and distribute the sunlight coming through the skylight dome on the roof.
Replacement skylight diffusers can become yellowed, brittle or cracked due to age and UV exposure. When this happens the diffuser can usually be replaced on its own without replacing the entire skylight. Identifying the correct diffuser shape and measuring the ceiling opening will help determine the right replacement size for your skylight.
If your skylight cover has become yellow, cracked or brittle, see our Skylight Cover Replacement Guide.
Other Skylight Parts
In addition to domes and diffusers, skylights also include several other components that may occasionally need replacing. These can include skylight shafts, flashings, ceiling frames and fixing hardware, depending on the type of skylight installed. While these parts generally last longer than domes or diffusers, they may need replacement if they become damaged, deteriorate over time or are affected during roof repairs.
If your skylight dome and diffuser are still in good condition but you are experiencing issues such as leaks, poor sealing or structural damage, the problem may relate to another skylight component. Identifying which part of the skylight system requires attention will help you choose the correct replacement part before ordering.
| How to Identify Your Skylight Dome
The skylight dome is the protective cover located on the roof. It allows natural light to enter your skylight while protecting the opening from rain, wind and debris. Over time skylight domes can become brittle or cracked due to sun exposure, hail or general weathering. When this happens, replacing the dome is often the quickest and most cost-effective repair.
To identify the correct replacement skylight dome, start by looking at the shape of the existing dome and measuring where it sits on the skylight base. Most residential skylight domes in Australia are square and come in common sizes such as 650 x 650, 750 x 750 and 800 x 800. Measuring the outside edge of the dome will help determine which replacement size you need.
If the dome has already been removed or damaged, you can often identify the correct size by measuring the skylight base or roof opening. The sections below explain how to measure your skylight dome and match it with the correct replacement.
Look at the dome shape
Skylight domes come in a range of shapes, with the most common being square, rectangular and round. The dome profile can also vary, with some skylights having a lower flatter dome and others having a taller more raised shape. Identifying the overall shape of your existing dome is an important first step when choosing a replacement.
While dome height and profile can differ between skylight models, the most important detail is matching the shape and internal diameter/base size of the existing dome. Once you have confirmed whether your skylight dome is square, rectangular or round, the next step is to measure the base of the dome to help identify the correct replacement.
Measure the dome diameter or edge to edge
Start by measuring the overall size of the skylight dome. For round domes, measure the diameter across the centre from edge to edge. For square or rectangular domes, measure the outside edge to outside edge of the dome base. This gives a general reference for the dome size.
The most important measurement, however, is the internal diameter of the dome base. This measurement determines the size of the skylight opening that the dome is designed to cover, which is the key factor when selecting the correct replacement. Find further information via our skylight measuring guides.
If the dome is missing or has been smashed, the best measurement to take is the skylight opening itself. Measuring the opening will provide a strong indication of the dome size required. This opening size can often be determined by measuring the skylight shaft, which may also be accessible from inside the home by removing the diffuser at ceiling level.
Common skylight dome sizes
Many residential skylights in Australia follow a number of common dome sizes, which can help narrow down the correct replacement once measurements have been taken. Some of the most frequently encountered sizes include 420mm, 450mm and 520mm, although other sizes may also exist depending on the skylight manufacturer and installation.
These sizes generally relate to the opening of the skylight base that the dome is designed to cover. While the overall outside measurement of the dome can vary slightly depending on the dome profile or manufacturer, matching the dome to the skylight opening size will usually lead you to the correct replacement. Taking accurate measurements will help confirm which of the common skylight dome sizes is most suitable for your skylight.
| How to Identify Your Skylight Diffuser
The skylight diffuser is the panel located in the ceiling that spreads natural light from the skylight evenly into the room below. Diffusers are typically made from acrylic or plastic and are designed to soften and distribute the sunlight coming down the skylight shaft. Over time diffusers can become yellowed, brittle or cracked, which is why replacing the diffuser is one of the most common skylight repairs inside the home.
To identify the correct replacement skylight diffuser, start by confirming the shape of the diffuser and then measure the ceiling opening where the diffuser sits. Most residential skylight diffusers are square, although rectangular and round diffusers are also used in some installations. Measuring the ceiling opening will help determine the correct diffuser size and guide you to the appropriate replacement panel.
Look at the diffuser shape
Start by identifying the overall shape of the skylight diffuser installed in the ceiling. Most residential skylight diffusers are square, but some installations use rectangular or round diffusers depending on the skylight design and the size of the ceiling opening.
The diffuser shape should match the skylight opening and the shaft above it. Confirming whether the diffuser is square, rectangular or round will help narrow down the correct replacement before taking measurements. Once the shape has been identified, the next step is to measure the ceiling opening to determine the correct diffuser size.
How does the diffuser attach
Before removing the diffuser, it helps to understand how it is attached to the skylight ceiling frame. Most skylight diffusers are designed to be removable so they can be cleaned or replaced, and there are a few common ways they are secured in place.
Many diffusers simply sit on an internal lip or ledge inside the ceiling ring, allowing the panel to be lifted out once access is gained. Some skylights use a twist-and-lock system, where the diffuser rotates slightly and locks onto small lugs in the frame. Another common design uses a bolt or fixing through the centre of the diffuser, which secures the panel to the skylight frame.
In some less common designs the diffuser may snap into place around the ceiling insert, clipping onto supports around the frame. Identifying how the diffuser is attached will make it easier to safely remove the panel so the opening can be measured for the correct replacement.
Measure the diameter of the diffuser
Once the diffuser has been removed, measure the diameter for round diffusers or the edge-to-edge width for square or rectangular diffusers. This measurement should be taken across the widest point of the diffuser panel and will help determine the correct replacement size.
If the diffuser is smashed or missing, the best measurement to take is the ceiling opening or ceiling mount where the diffuser normally sits. Measuring this opening will usually provide a reliable guide to the diffuser size required.
If possible, it is also helpful to send a photo of any remaining diffuser fragments and the ceiling insert or frame. This can often reveal important details such as the skylight model or mounting style, which helps confirm the correct replacement diffuser before ordering.
Common skylight diffuser sizes
Many residential skylights in Australia use standard diffuser sizes, which can help narrow down the correct replacement once the ceiling opening has been measured. Some of the most common diffuser sizes include 300mm, 400mm, 455mm and 500mm, although other sizes may exist depending on the skylight manufacturer and installation.
These measurements typically relate to the ceiling opening or skylight shaft size that the diffuser covers, rather than the overall outside dimensions of the diffuser panel itself. Matching the diffuser to the ceiling opening size will usually lead you to the correct replacement. Taking an accurate measurement of the opening will help confirm which of the common skylight diffuser sizes is most suitable for your skylight.
| Common Skylight Found in Australian Homes
Many residential skylights installed across Australia follow a number of common sizes and designs, particularly in homes built from the 1980s through to the early 2000s when skylights became widely used in bathrooms, hallways and kitchens. While there are many different skylight brands and models, a large number of installations share similar dome, diffuser and shaft sizes, making replacement parts easier to identify once basic measurements have been taken.
Some of the most frequently encountered skylight sizes include 400mm, 455mm and 500mm, with square skylights being the most common design in residential homes. Identifying the general size of your skylight, along with the shape and mounting style of the dome or diffuser, will help narrow down the correct replacement part. The sections below outline some of the skylight sizes most commonly found in Australian homes.
| What Happens Next
Once submitted, we’ll review your photos and measurements to identify the correct replacement part.
- We review your photos and measurements
- We identify the correct skylight part
- We confirm the best match before you order
If we need more details, we’ll contact you — no guesswork, no risk of ordering the wrong part.
| Skylight Identification FAQs
How do I identify what skylight I have?
Start by identifying which skylight component you are replacing. The most common parts that require replacement are the skylight dome on the roof or the skylight diffuser inside the ceiling. Once the part has been identified, measuring the skylight opening or panel size will help determine the correct replacement. Looking at the shape of the dome or diffuser and taking a few simple measurements will usually narrow down the correct skylight part.
What is the most common skylight size?
Many residential skylights installed in Australian homes follow common sizes such as 300mm, 400mm, 455mm and 500mm. Among these, 455mm skylight diffusers are one of the most frequently encountered sizes, particularly in hallways, bathrooms and kitchens where skylights are commonly installed.
Can I replace just the skylight dome?
Yes. In many cases the skylight dome can be replaced without replacing the entire skylight unit. If the dome has become brittle, cracked or damaged by hail, replacing the dome is usually the quickest and most cost-effective repair. As long as the skylight frame and flashing are still in good condition, a replacement dome will restore the skylight’s weather protection and light entry.
Can I replace just the skylight diffuser?
Yes. The skylight diffuser can normally be replaced on its own without replacing the rest of the skylight. If the diffuser has become yellowed, brittle or cracked, installing a new diffuser can restore the appearance of the skylight and improve how light is distributed throughout the room.
How do I measure a skylight dome?
Measure the base of the skylight dome where it sits on the skylight frame. For round domes measure the diameter across the centre, and for square or rectangular domes measure edge to edge across the base. The internal diameter of the dome base is often the most important measurement because it determines the size of the skylight opening the dome is designed to cover.
How do I measure a skylight diffuser?
Remove the diffuser panel and measure the diameter for round diffusers or the edge-to-edge width for square diffusers. If the diffuser is damaged or missing, measuring the ceiling opening or skylight shaft size will usually provide a reliable guide to the correct replacement diffuser size.
What should I do if I cannot identify my skylight?
If you are unsure which skylight part you need, the easiest solution is to send us a photo of your skylight along with any measurements you have taken. Photos of the dome, diffuser, ceiling frame or skylight shaft opening often reveal details that help confirm the correct replacement part before ordering.