Shade Cloth Explained: 30%, 40%, 50% or 70% — Which Do You Need?
Shade cloth is sold by percentage — the amount of sunlight it blocks — and picking the wrong number is the most common mistake we see. Here is what the percentages actually mean in a UK garden.
UK sun is real — for about six weeks
Shade cloth choices in Britain are different from hotter climates: you are usually shading a conservatory-facing patio or a greenhouse for the June–July peak, not building year-round shade. That argues for lighter percentages than the tropics-oriented advice you will find online, and for fixings you can take down in September. South- and west-facing spots need the most help; an east-facing patio that only gets morning sun rarely needs more than 30–40%.
The percentages, translated
- 30–40%: light dappled shade. Ideal for vegetables and greenhouse crops in a British summer — tomatoes, peppers and salads keep growing but stop scorching. This is the right default for most UK growers.
- 50%: the all-rounder. Good for mixed borders, nursery benches and pet runs; noticeably cooler underneath without feeling dark.
- 70%: serious shade. For seating areas, shade-loving plants (ferns, hostas), chicken runs and car protection. Too dark for most edibles.
Greenhouse or patio?
In a greenhouse, fix the cloth on the outside of the glass if you can — it stops the heat before it enters, which is far more effective than internal shading. Over a patio or pergola, tension matters more than density: a taut cloth sheds wind and looks intentional, a saggy one flaps and frays. Our shade cloth collection carries 30% to 70% densities with reinforced grommets for exactly this.
Fitting tips that save frustration
- Use every grommet, not just the corners — load spread is what stops tears in gusts.
- Attach with bungee ties rather than rigid rope; the give protects the grommets in wind.
- HDPE mesh is breathable — rain gets through, so plants underneath still get watered.
- Take it down for winter storms; ten minutes of effort doubles the lifespan.
Quick answers
How do I fix shade cloth so it survives wind?
Tension is everything. Fix through grommets with bungee cord or ball ties rather than rigid rope — the give absorbs gusts instead of tearing the cloth. Anchor to solid points (fence posts, wall eyes, pergola beams), never to gutters. If your garden is exposed, choose knitted cloth over woven: it stretches slightly and lets wind bleed through.
Will shade cloth stop my greenhouse overheating?
It is the single most effective fix. External shading beats internal blinds because it stops heat before the glass. A 40–50% knitted cloth over the roof panel, clipped so there is an air gap, typically pulls a UK greenhouse down by 5–8°C on a sunny afternoon — enough to stop tomatoes aborting flowers.
