Get the Best Performance from Your Fiberglass Roofing

Fiberglass sheeting is one of the most durable and reliable roofing solutions available in South Africa. It is UV-stabilised, long-lasting, and ideal for residential, agricultural, and industrial use.

However, even the highest quality fiberglass roofing sheets can fail early if installed incorrectly. Mistakes during installation often lead to leaks, cracking, poor drainage, or unnecessary repairs.

Below are five common fiberglass roofing installation errors and how to avoid them.

1. Incorrect Sheet Overlap

One of the most common causes of roof leaks is insufficient overlap between sheets. If the overlap is too small, water can enter during heavy rain or wind-driven storms.

How to avoid it

• Always overlap the sheet according to its profile
• Ensure side laps and end laps are aligned correctly
• Avoid leaving gaps between sheets

Proper overlap improves water flow and strengthens the roof against wind uplift.

2. Over-Tightening Screws

Fiberglass sheets expand and contract naturally due to temperature changes. Over-tightening fasteners can cause stress points, leading to cracking over time.

How to avoid it

• Tighten screws firmly but do not force them
• Use roofing screws with rubber washers
• Allow natural movement without pressure damage

This helps prevent long-term structural stress.

3. Drilling Holes Incorrectly

If holes are drilled too small, the fiberglass can crack when it expands. If holes are drilled in the wrong position, the sheet may shift or leak.

How to avoid it

• Drill holes slightly larger than the screw size
• Drill on the correct section of the profile
• Use the correct drill bit and low-speed drilling

Correct drilling ensures durability and prevents unnecessary fractures.

4. Poor Support Spacing

Fiberglass roofing requires proper support underneath. If purlins or rafters are spaced too far apart, the sheet may sag, flex excessively, or weaken over time.

How to avoid it

• Ensure support structures are installed at correct intervals
• Use thicker fiberglass sheets for larger spans
• Avoid walking directly on unsupported sections

Good spacing improves safety and strengthens the roof’s performance.

5. Ignoring Roof Pitch and Water Drainage

A roof with insufficient slope may cause standing water, which increases the risk of leaks and long-term wear.

How to avoid it

• Install fiberglass roofing with a proper pitch
• Ensure runoff flows toward gutters or drainage areas
• Avoid flat roofing without professional guidance

A well-pitched roof ensures water drains efficiently during heavy rainfall.

Fiberglass Installation Mistakes Summary Table