Shed Windows Cut To Size

The right material depends on the size of your window, your budget and the level of impact resistance required.

Clear acrylic sheet

Clear acrylic is usually the best option for a standard shed window replacement where cost and appearance are the main priorities. It is lightweight, provides clear visibility, and is easier to handle than glass. Acrylic is naturally UV stable and does not yellow over time, making it a long-lasting choice for outdoor use.

Choose acrylic when:

• You want an affordable replacement for broken shed glass
• The sheet will be supported around all four edges
• The window is not exposed to frequent impacts
• You want a clear, traditional-looking window

Clear polycarbonate sheet

Polycarbonate is more impact resistant than acrylic and is better suited to sheds located near play areas, pathways or exposed locations. It is also a stronger option where security is an important consideration. Clear polycarbonate sheets are highly resistant to heat and UV radiation and do not yellow in the sun, making them ideal for outdoor use.

Choose polycarbonate when:

• The window is at greater risk of impact
• Children regularly play near the shed
• You require additional security
• The window opening is larger or less well supported

For most small garden shed windows, 3mm acrylic provides a practical and economical replacement. Larger sheets are more likely to flex, so a thicker material or additional frame support may be required.

Where impact resistance is more important than price, choose polycarbonate rather than increasing the thickness of acrylic alone.

Accurate measurements are essential when ordering a replacement shed window. Before measuring, identify whether the new sheet will sit inside the existing frame rebate or be fitted over the opening.

If the sheet will sit inside the frame

• Remove the damaged glass or existing panel where it is safe to do so.
• Measure the width of the rebate at the top, middle and bottom.
• Measure the height at the left, centre and right.
• Use the smallest width and height measurements.
• Deduct a small amount to prevent the acrylic from fitting too tightly.

For a typical small shed window, allowing approximately 2–3mm of total clearance across both the width and height will help accommodate slight frame irregularities and material expansion.

If the sheet will cover the opening

Measure the full width and height of the opening, then add enough overlap for the sheet to be securely fixed to the surrounding timber.

The amount of overlap required will depend on the fixing method, but the acrylic should extend far enough beyond the opening for screws, clips or glazing beads to hold it securely.

Before ordering, check that:

• The frame is reasonably square
• The timber is not rotten or severely damaged
• The sheet will not be forced tightly into the rebate
• Your measurements are entered in millimetres
• You have selected the correct thickness and material

There are several ways to secure an acrylic or polycarbonate sheet to a timber shed.

Fit the sheet inside the existing rebate

This is the most traditional method. The sheet sits inside the existing window frame and is held in place using timber glazing beads, glazing clips or panel pins.

This method provides a neat finish and is suitable where the original frame remains in good condition.

Fit the sheet over the opening

The plastic sheet can also be mounted over the window opening and secured directly to the surrounding timber.

This may be suitable where:

• The original rebate is damaged
• The opening is irregular
• A quick and economical repair is required

The sheet should overlap the opening sufficiently for the fixings to be positioned securely in the surrounding timber.

Fix the sheet with screws

Acrylic and polycarbonate can be fixed using screws and suitable washers. The fixing holes should be 2–3 mm larger than the screw shaft to allow for material movement. Keep a minimum edge distance of approximately 10 mm, or 1.5 to 2 times the screw diameter. Do not overtighten the screws, as this can cause stress around the fixing holes and may lead to cracking.

The replacement sheet must be fitted securely enough to prevent rain from entering around the edges.

Before sealing the window:

• Make sure the frame is clean and dry
• Repair rotten or damaged timber
• Check that the panel sits flat
• Remove loose paint and old sealant
• Confirm that any drainage points remain clear

Use a sealant or glazing product that is suitable for both the plastic sheet and the surrounding frame material.

Apply the sealant evenly around the exposed joints, but avoid using excessive amounts. A large bead of sealant will not compensate for a damaged or uneven frame.

Inspect the window after heavy rain and reseal any areas where water is entering.

Ordering the sheet to the exact rebate size

Acrylic should not be forced tightly into the frame. Leave a small clearance around the edges to account for uneven timber and material expansion.

Choosing a sheet that is too thin

Thin acrylic may flex or bow in a large opening. Choose a thicker sheet or add additional frame support where required.

Overtightening screws

Screws should secure the window without clamping the material tightly. Excessive pressure can cause cracking around the fixing holes.

Drilling too close to the edge

Fixing holes positioned too close to the edge of the sheet are more likely to crack. Keep a minimum distance of approximately 10 mm, or 1.5 to 2 times the screw diameter, from the edge.

Sealing over damaged timber

Sealant will not provide a long-term repair if the surrounding frame is rotten or unstable. Repair the timber before fitting the new window.

Removing the protective film too early

Keep the protective film in place while measuring, positioning and drilling the sheet. Remove it only after installation is complete.