“Waterproof and breathable” is printed on nearly every turnout rug. The two words are easy to say and hard to verify. Here is what the spec numbers actually mean.
Denier: The Shell Strength
Denier (D) measures the thickness of the outer fabric yarn. Common shell weights are 600D, 840D, 1200D and 1680D. Higher denier means a tougher shell — important for turnout rugs that meet trees and fences. For stable rugs, 600D is usually enough. Denier is about durability, not waterproofing.
Hydrostatic Head: The Waterproofing Number
Hydrostatic head measures how much water pressure a fabric resists before leaking, in millimetres. A rug rated 5,000mm is genuinely waterproof for normal rain; 10,000mm+ is for heavy, sustained rain. If the label does not state a hydrostatic head, the waterproofing claim is unverified — ask for the number.
Breathability: The Sweat Problem
A waterproof shell that cannot breathe turns the rug into a sauna — the horse sweats underneath and the fill becomes damp. Breathability is measured in how much moisture vapour passes through the fabric (g/m²/24h). Higher is better: a breathable turnout rug lets sweat escape while keeping rain out.
Seam Taping
Most waterproof shells leak at the seams, not the fabric. Taped seams cover the stitch holes with waterproof tape — the detail that separates a real turnout rug from a stable rug that merely looks waterproof. Check it before you order.
When Buying in Bulk
For brands, the spec sheet should state denier, hydrostatic head, breathability and seam taping per SKU — and the sample should be tested, not just read. A simple rain test on the sample tells you more than a brochure.
HorseMerch manufactures fly sheets and turnout rugs with fixed waterproof and breathable specs. Ask us for the numbers on any model.
Related Guides
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Sourcing the products in this guide: browse our horse rugs and fly sheets, see the 100g Lightweight Waterproof Turnout Rug Standard Neck 600D and 200g Mediumweight Combo Turnout Rug Full Neck 600D Waterproof, or request a quotation for factory-direct pricing, MOQ, samples and lead times.