How to Measure a Skylight? A Step by Step Guide

Measurement accuracy for your skylight is one of the more critical steps. If you are installing a new one or replacing an old skylight, ensuring correct measurement from your end improves the chances of a perfect fit, minimisation of leaks and better energy efficiency. To best serve you, we'll describe each step to ensure maximum accuracy.

The Importance of Accurate Measurements

Correct measurements go beyond checking if your skylight is fitting into the opening; it also helps mitigate potential issues. A skylight that has been measured accurately will:

Be easy to install
Waterproof seal using your roof.
Achieve optimal thermal performance.
Supply the right amount of natural light.
No expensive adjustments needed for installation.

Spending time with the tape measure now will save hassle in the future.

Must-Have Tools You'll Need

Double-check this list before heading up to the roof so you do not forget anything:

● A strong ladder that can safely reach your roof is necessary. Make sure it is stable and at level.

● An equally important item to carry would be a metal tape measure, making sure to exclude stretchy measuring tapes that can add or subtract up to cm's.

● To support better memories, especially when completing an important task, writing down notes in a notebook is much better than recalling things from memory.

● A spirit level is extremely essential in considering roof pitch when determining it as it is useful in checking if surfaces are level.

● When working at heights, footwear such as shoes that are non-slip as well as protective eye gear fall under the category of working safety equipment and are essential.

● Having photos taken using your phone is much easier when saving them as backup and it also simplifies communication with suppliers regarding measurements.

Classifications of Skylights Useful for You

As far as measuring goes, each skylight has its own approach:

● Deck mounted skylights have a frame that is mounted straight on top of the roof deck, thus the frame is parallel with the roofing shingle. More recently built houses usually have this type.

● Curb mounted skylights are placed on a square frame higher than the roofline. This square perimeter serves as a water diversion.

● Tubular skylights are smaller, cylindrical units that are mounted on ceilings, where they channel light from the roof through a reflective tube. They’re most commonly used in small rooms and spaces where traditional sized skylights are out of the question.

As you finish reading this, I hope you know what type of skylight you have or will plan on installing, so it makes measurement easier.

Measuring to Replace a Fitted Skylight

Step 1: Search for Identifying Details

Skylights usually have an identification label somewhere on the perimeter. For deck-mounted units, inspect the internal border. For curb-mounted ones, check the outer sides. Sometimes the identification is engraved on the spacer bars located between the glass panes.

Even if you do come across such information, it is handy but not conclusive. Models change over time and the older information may leave out essential factors, or lacking considerations could lead you to vital under-measured dimensions.

Step 2: Take Exterior Measurements

For deck-mounted skylights: Measure the length and width of the exterior glass pane from the inside edge of the adornments. For openings of the skylight, take measurements around the frame as they are not always square.

For curb-mounted skylights: Take both outside curb dimensions, glass dimensions and any other relevant aspects such as roofing membranes.

Clearly record all measurements, indicating the specifics of each metric.

Step 3: Internal Measurement

The parameters of your house's windows and the sight lines from the rooms matter just as much as the exterior roof openings:

Note the dimensions of the drywall opening if it is accessible: Measure the W/L of the skylight and also note the distance from the ceiling to the base frame of the skylight.

These measurements will enlighten you on the full extent of the relevant geometry’s spatial composition.

Step 4: Verify Whether the Opening is Square

Measure each diagonal from corner to corner in both ways. If both measurements are equal, then your opening is a perfect square. If not, note the difference as this will affect how the frame is installed.

Non-square openings are surprisingly common, particularly in houses that have aged or ‘settled’ over time.

Measuring for a New Skylight Installation

Step 1: Select Proper Dimensions and Place with Purpose

As a rule of thumb, a skylight should be 5% to 10% of the room's size for adequate illumination. Make sure to evaluate the skylight's positioning in regard to the room's floor area.

Reflect on south-facing skylights which receive maximum direct sunlight, compared to north-facing which receives softer, more balanced exposure.

Step 2: Finding Structural Elements

Before planning your opening, mark out any rafters or joists that may interfere with placement. In most UK homes, standard rafters are set at intervals of 40cm or 60cm.

Working with existing site conditions above where you intend to place the skylight will reduce the amount of modification required, thus simplifying your project.

Step 3: Plan Your Opening Size

Work out what size skylight will be usable within the spacing between rafters to avoid extensive remodeling. Prefabricated skylights are easier to obtain and cheaper than custom ones.

You will need to strengthen the cut rafters by adding supports if the skylight placed will require reinforcement to be structurally sound.

Step 4: Consider Roof Pitch

Both, the type of skylight you choose and the method of installation are determined by the angle of your roof. To assess pitch:

● Using a manometer, position it horizontally on the roof surface.

● Take note of the vertical distance from the end of the level to the surface of the roof.

● This offers you rise over a specified run.

This info is essential while picking out the correct flashing kit for your skylight.

Important Features to Keep in Mind

When taking measurements, pay attention to these features:

● Fixed vs Opening: Framed fixed rooflights do not open and provide better insulation. Opening skylights provide ventilation but need headroom clearance when opened.

● Glass Options: Clear glass offers no privacy which makes it easier for light transmission. For bathrooms or bedrooms, privacy glass would be better especially when exposed to outside view.

● Energy Efficiency: In the UK, it is important to pay attention to the units with good insulation values (low u-values) to minimise heat loss.

Be careful of these common mistakes:

● One of the biggest mistakes people make is mixing up different points of measurement. The rough opening, frame size, and visible glass area are all different measurements.

● Measuring across all three dimensions is dangerous if done in only a single point. You must measure at several points and use the smallest measurement to ensure your skylight will fit.

● Overlooking measuring specifics can lead to other issues. Different roof types and slopes come with their own specialised flashing systems that affect your measurements.

● Not including the thickness of the drywall when measuring the closed systems boundaries can lead to problems when integrating the results. When designing spatial arrangements, ceiling material thickness should always be factored in.

With some skills in DIY, it is possible to install a skylight, especially one that is a fixed, flat rooflight.

Your home or building will surely benefit a lot if it is protected from water leaks, thus having a professional do the installation provides tangible benefits as they can guarantee that the required standards have been met and are also able to fix any gaps should they arise, offering good value for money.

No matter the approach you take, ensuring accuracy when taking measurements is vital.

Skylight orders should not be finalised until:

Every single measurement has been checked and validated. It is always better to take two measurements rather than encounter numerous issues during the installation phase.
Confirm your roof pitch along with the material so that you can select the flashing kit properly.
Consider what type of skylight best serves your particular requirements paying attention to ventilation, energy effectiveness, and privacy needs.
Verify with your supplier any special requirements to ensure that you get what you want.

Conclusion

Although getting your skylight measurements involves basic techniques, it requires a precise approach. Measuring correctly saves time during the installation process while ensuring the skylight functions optimally for years.

Whether you're brightening a dark room or replacing an old unit, correct measurements are integral to successful outcomes. As an aside, professional guidance is often a wise choice if you find yourself in a predicament with measuring or installation.

For any inquiries related to skylight selections, measurements or installation, our team is glad to assist. Reach out to us and let the right skylight illuminate your space with natural light.