How to Measure for Clear PVC Tarps

Clear PVC tarps must fit tightly to block wind, prevent flapping, and create a proper enclosure. Unlike fabric, PVC doesn't stretch — which means good installation depends entirely on correct measuring.

The steps below apply to patios, pergolas, gazebos, porches, and detached outdoor structures.

1. Measure the Opening — Not the Frame

You want the tarp to cover the open section, not wrap around posts. Measure inside the frame where the tarp will be mounted.

Measure width:

• Left post inner edge → right post inner edge

Measure height:

• Bottom of beam → top of railing or floor

Write down the "true opening size." Everything else is calculated from this.

2. Account for Mounting Hardware Space

PVC tarps include hems and grommets. These take up space and must be considered in advance.

• Add 1 inch to the top for hardware clearance
• Add 1 inch to the bottom if a weighted hem or rail is used
• Leave ½ inch gap at sides to avoid rubbing against posts

Don't design a "perfectly tight" tarp — PVC expands in heat and tightens in cold.

3. Choose Your Mounting Style

The mounting method determines your final measurements. Here are the three most common styles:

A. Under-Beam Mount (Most Common)

The tarp attaches to the underside of a pergola beam or gazebo roof.

• Width = true opening minus ½ inch
• Height = true opening minus 1 inch

B. Face-Mount to Posts

The tarp mounts directly onto the front of the structure.

• Add 1–2 inches to width for side overlap (optional)
• Add 1–2 inches to height for top and bottom overlap

This is best when blocking drafts is a priority.

C. Track System Mount

The tarp slides into a top track for a rigid, clean look.

• Width = exact opening width
• Height = opening height minus the track height

Track systems require the most precise measurements.

4. Divide Long Openings into Multiple Panels

Any opening wider than 8–10 feet should be split into smaller panels. This improves:

• Wind stability
• Noise reduction
• Ease of installation
• Lifespan of PVC

Example: A 16 ft opening becomes two 8 ft panels.

More on wind behavior:
PVC Wind Behavior Guide

5. Decide on Bottom Anchoring Before You Order

Bottom anchoring affects the final height measurement.

If using a bottom rail or weight:

Subtract 1 inch from final height.

If using bungees to hooks or eyelets:

No change needed — bungees absorb movement.

6. Add a Door or Roll-Up Section (Optional but Highly Useful)

If you need daily entry to the space, measure for a:

• Roll-up panel on one section
• Zipper door within a fixed panel
• Overlapping flap door (budget option)

Doors are almost always ordered as separate panels for best alignment.

7. Re-Measure Everything Once

After calculating adjustments, re-measure the opening and confirm:

• Top mounting point height
• Bottom anchoring height
• Side wall alignment
• That the opening is square — not leaning

If one side is taller than the other, order panels to the shorter height.

8. Most Common Measuring Mistakes (Avoid These!)

• Measuring the outside of posts instead of the inside
• Forgetting hardware clearance
• Ordering one giant tarp for a long pergola side
• Not allowing room for expansion and contraction
• Assuming the opening is perfectly level (it rarely is)

Summary

A correctly sized PVC panel fits snugly, blocks drafts, and stays quiet in wind. Measure inside the frame, account for hardware, split large openings, and choose the right mounting method.

Back to the hub: Clear PVC Tarps & Outdoor Enclosures