The autumn treatment is done. The driveway's been treated, the patio's been sealed, the decking's had its annual clean. Now the bottles go back in the shed, and that's where most people stop thinking about it.

It's worth thinking a little further. Exterior cleaning products stored incorrectly over winter can fail silently: a sealer that looks fine in the bottle but has broken down and won't cure, a biocide that's been diluted by condensation, a concentrate that's been compromised by freeze-thaw cycling. You won't know until you open the bottle next spring and wonder why it isn't working.

This guide covers how to store GK's exterior cleaning products correctly over winter, what to check before putting them away, and what to do if you're not sure whether a product is still viable.

Why Winter Storage Matters More Than You Might Think

Most cleaning chemicals are stable under normal conditions. The problems come from specific winter storage risks:

Freezing: Water-based products such as sealers, emulsion-based cleaners, anything with a milky or cream consistency, can be permanently destroyed by a single freeze event. The low temperatures most British sheds experience during a cold spell are enough to rupture emulsions and coagulate polymer particles. Once this happens, the product cannot be recovered by warming it up or shaking it.

Repeated freeze-thaw cycling: Even products that survive a single frost can be degraded by repeated freeze-thaw cycles over a winter. Each cycle stresses the chemical structure. Surfactant-based products can see changes in their emulsification properties. Biocidal actives can be affected by repeated crystallisation and rehydration.

Condensation dilution: Products stored in sheds or outbuildings that experience significant temperature swings accumulate condensation inside partly-filled containers. Over a winter, this can measurably dilute a concentrate, affecting the working dilution calculations you'd normally apply in spring.

UV and light exposure: Some biocidal actives are sensitive to prolonged light exposure. Products stored on open shelves near windows or skylights over several months can see gradual degradation of the active ingredient.

Cross-contamination: Containers stored near other chemicals, fuels, or solvents can be affected by vapour migration if lids aren't fully sealed.

None of these risks requires a dramatic event like a burst pipe, a flood, or an accident. They accumulate quietly across a winter of neglect.

The Golden Rule: Frost-Free Storage

For all GK exterior cleaning products, the single most important storage requirement is frost-free conditions.

This means a location where temperatures reliably stay above 0°C throughout winter; not just usually above freezing, but consistently so. A brick-built garage or outbuilding that retains some heat from its thermal mass is generally fine. A thin-walled metal shed or a lean-to that drops to ambient outdoor temperature overnight is not reliable enough for water-based products.

If you only have outdoor storage available, water-based sealers in particular should be brought indoors for the winter, either into a utility room, a kitchen cupboard, or any reliably heated space. They don't need to be warm; they just need to be above freezing.

The products where this matters most:

• GK Invisible Stone Sealer: water-based emulsion, permanently damaged by freezing. Bring indoors.
• GK Invisible Wood Sealer: water-based emulsion, permanently damaged by freezing. Bring indoors.

The products where this is still advisable but less critical:

• GK Pro: DDAC-based biocide, more tolerant of cold than emulsion products but should still be stored above freezing where possible.
• GK Path & Patio Cleaner, Driveway Cleaner, Render Cleaner, Decking Cleaner: surfactant-based cleaners that are more cold-tolerant than emulsions but benefit from frost-free storage.
• GK Concentrated Fungicidal Wash, GK Mould & Mildew Cleaner: store above freezing where possible.

Before You Put Products Away: A Quick Check

Before sealing containers for winter, do a quick pre-storage check. It takes two minutes and avoids unpleasant discoveries in spring.

1. Check the lid seal. If a lid has been opened and reclosed over a season of use, check it's properly sealed, not just clicked shut but actually tight. A loose lid allows moisture ingress and vapour loss over winter. If in doubt, seal with a single wrap of PTFE tape around the thread before closing.

2. Note what's left. Record approximately how much product remains in each container either with a marker pen on the label or a note on your phone. In spring, this tells you whether you have enough for a maintenance application or need to order before you start. It also gives you a baseline: if a container feels significantly lighter or heavier in spring than your note suggests, something has happened to it.

3. Check the appearance. For emulsion products (sealers), note the appearance before storage. A uniform, milky or cream-coloured liquid is correct. If a product already shows separation, graining, or has an unusual texture before winter storage, it may have already been compromised by cold; treat it as suspect and check its performance carefully before using it on a large area.

4. Check the use-by or best-before date. Most professional cleaning chemicals have a shelf life of two to three years from manufacture. If a product is approaching or past this date, it may not perform reliably even if stored perfectly. Check the label and plan to replace if necessary before the next season.

How to Store Each Product Type

Sealers (Stone and Wood)

Bring indoors. Store in a location that stays consistently above 0°C. No direct sunlight. Keep the lids sealed tightly.

If you have a partly-used tin, consider whether it's worth decanting into a smaller container to reduce the air space above the product. Less air means less risk of a surface skin forming and less opportunity for condensation to accumulate.

GK Invisible Stone Sealer and GK Invisible Wood Sealer should not be stored in an unheated shed, garage without insulation, or any space that regularly drops below freezing overnight between November and March.

Biocidal Cleaners (GK Pro, Path & Patio, Driveway, Render, Decking)

These are more robust than emulsion products, but should still be stored in frost-free conditions where possible. In practice, a well-insulated garage or a shed that doesn't drop below -5°C is usually adequate for DDAC-based biocides, but below freezing is not ideal, and should be avoided if an alternative is available.

Store away from direct light. Keep the lids sealed. Do not store near fuels, solvents, or acids.

If you have a partly-used container of concentrated product, check the dilution markings on the label are still readable. If the label has been damaged over a season of outdoor use, make a note of the dilution ratios before storing.

GK Pro (Concentrated DDAC Biocide)

GK Pro is the most concentrated product in the GK range and should be stored with particular care. Frost-free, away from light, lid fully sealed. Do not store in direct contact with metal surfaces; use a shelf or plastic tray.

If you have an unused diluted working solution left over from a treatment job, do not store it. Diluted DDAC degrades faster than the concentrate, and a winter-stored diluted solution may not perform reliably in spring. Dispose of any leftover diluted solution appropriately, dilute further with water before disposal, in accordance with product guidelines.

Disposal: What to Do With Products You Won't Use Again

If you have products that are clearly compromised, a sealer that has already frozen and separated, or an almost-empty container that isn't worth carrying over, dispose of them responsibly.

Do not pour cleaning chemicals down a drain or into a garden drain. Professional biocidal cleaners containing DDAC are designed to kill biological organisms: that includes the biology in garden soil and waterways. Dispose of biocidal cleaners at a household waste recycling centre.

Most local authority recycling centres accept household and garden chemicals in the same section as paint and solvents. Check your local authority's website for opening times and accepted materials.

For very small quantities of residual product, dilute heavily with water before any disposal as this reduces concentration to a level that's manageable for water treatment processes. Do not do this for large quantities.

In Spring: How to Check Whether a Product Is Still Good

When you bring products out of storage in March or April, check them before committing to a large treatment.

For sealers: Pour a small quantity into a container and check the consistency. It should be uniform and milky, with no graining, lumps, or significant separation. Run it across a test area of your surface; water should bead on the sealed area within a few minutes. If the product soaks straight in with no beading, the sealer has not cured and is likely compromised.

For biocidal cleaners: A patch test on a heavily contaminated small area (a corner of the patio, a section of path) will tell you within a few days whether the product is performing. If biological growth shows no sign of yellowing, dying back, or lifting after a week at adequate temperatures, the product may have degraded.

If any product gives you doubts after winter storage, contact the GK team before treating a large area; it's far better to replace a £22.79 bottle than to re-treat an entire driveway because the product wasn't viable.

Quick Reference: Winter Storage Summary

 

Frequently Asked Questions

Can cleaning chemicals freeze in a shed?

Yes. UK sheds, particularly timber or metal-framed structures without insulation, regularly reach temperatures below 0°C during cold spells between November and February. Water-based products, including sealers, can freeze at these temperatures. A garage with brick or block walls retains significantly more heat than a thin-walled shed and is usually adequate for non-emulsion products. Sealers and emulsion paint should be brought indoors regardless.

How do I know if my sealer has frozen?

A sealer that has been frozen and thawed will typically show visible separation; the uniform milky liquid breaks down into a watery phase with lumps, grains, or a curd-like texture. The product may also smell different. If you're unsure, do a test application: a sealer that hasn't cured properly won't bead water on the surface within a few minutes of application.

Can I store a half-used bottle of GK Pro over winter?

Yes. GK Pro concentrate is relatively cold-tolerant compared to emulsion products, but should still be stored above freezing where possible. The more important rule is to never store a diluted working solution over winter. Diluted DDAC degrades faster than the concentrate and may not perform reliably after several months' storage. Dispose of any leftover diluted solution rather than storing it.

How long do GK products last in storage?

Most professional exterior cleaning products have a shelf life of two to three years from manufacture under correct storage conditions (frost-free, away from direct light, lid sealed). Check the best-before date on the label. Products that have been stored correctly and are within their shelf life should perform as expected in spring.

My shed gets cold but doesn't freeze, is that OK for cleaners?

For biocidal cleaners (Path & Patio, Driveway, Render, Decking, Pro), a consistently cold-but-not-freezing shed is generally adequate. For sealers and paint, bring them indoors. A shed that "doesn't usually freeze" can still hit 0°C on a sharp night, and that's all it takes to destroy an emulsion.

Should I decant products into smaller containers before storing?

For partly-used sealers, decanting into a smaller container reduces the air gap above the product, which minimises the risk of surface skinning and condensation accumulation. Use a clean container, label it clearly with the product name, dilution (if applicable) and date, and seal tightly. Don't mix different products in the same container.

Summary

Not sure whether a product is still good after winter storage? Send a photo or description to the GK team at sales@gkproductsuk.com or call 07557 111 297, we're happy to advise before you commit to treating a large area.