Walk into any DIY shop on a Saturday morning and you'll spot them instantly: someone standing in front of a wall of tins, looking properly baffled. Varnish, polyurethane, lacquer. They all promise a lovely finish, they all look roughly the same in the tin, and they all cost about the same too. So which one do you actually need for the job you've got planned?
The short answer: use varnish for outdoor wood like doors, gates, and garden furniture. Use polyurethane for hardwearing indoor surfaces like floors, stairs, and worktops. Use lacquer for decorative indoor furniture where you want a smooth, glossy finish. The rest of this guide explains why, so you can pick with confidence.
If you've been putting off restoring that old oak dresser, or you're finally ready to sort out the scuffed floorboards in the hallway, this is for you. We'll break down what each finish actually does, where it shines, and where it falls a bit flat. By the time you're done reading, you'll be able to walk into the shop (or browse Trade Supplies UK from the sofa with a cuppa) knowing exactly what to reach for.
What is the Difference Between Varnish, Polyurethane, and Lacquer?
All three are clear wood finishes that protect timber and enhance its appearance, but they differ in chemistry, durability, drying time, and ideal use case. Varnish is oil or resin based and built for weather resistance. Polyurethane is a synthetic resin-based finish known for its durability. Lacquer is a fast drying solvent based finish prized for its smooth, glossy look.
Think of it like choosing between wellies, trainers, and brogues. They're all shoes, but you wouldn't wear brogues on a muddy walk in the Lake District, and you'd look odd turning up to a wedding in wellies.
Quick Comparison at a Glance
- Varnish: Weather resistant, slow drying (8 to 24 hours), best for exterior wood, contains UV filters in exterior grades.
- Polyurethane: Extremely tough, moderate drying time (2 to 8 hours), best for high traffic indoor surfaces, available in water or oil based.
- Lacquer: Very fast drying (around 30 minutes), glossy finish, best for decorative indoor furniture, usually sprayed.
What is Varnish Used For?
Varnish is primarily used for exterior wood protection in UK homes. It has been around for centuries and remains the go to option when you need a finish that stands up to the British weather.
Varnish is typically a blend of resins, oils, and solvents. It dries slowly, which can feel like a faff if you're impatient, but that slow dry time is exactly what gives you such a smooth finish. Exterior varnish (often called yacht varnish) also contains UV filters, which stop the sun from bleaching the wood. That matters even on our drizzly little island. A stretch of sunny August afternoons can do more damage to an untreated front door than you'd think.
When to Use Varnish
- Front doors that face the weather all year round
- Garden benches, gates, and sheds
- Wooden window frames, especially on period properties
- Outdoor furniture you actually want to last longer than one summer
- Boats, decking, and anything exposed to moisture
If you live in a Victorian terrace with original timber sash windows, a good quality exterior varnish is often your best mate.
What is Polyurethane Used For?
Polyurethane is used for high traffic indoor wood surfaces that need to resist scratches, scuffs, and spills. It's the more modern cousin of varnish, a synthetic finish sold as either water based or oil based.
Polyurethane is known for being seriously tough. We're talking scuff resistant, scratch resistant, and fairly unbothered by spilled tea, wine, or whatever else ends up on your floor on a Sunday afternoon. Water based polyurethane dries quickly, stays clear over time, and barely smells of anything. Oil based polyurethane takes longer to cure, but it adds a warm, slightly amber glow to the wood that looks gorgeous on darker timbers like oak or walnut.
When to Use Polyurethane
- Wooden flooring in hallways, kitchens, and living rooms
- Staircases that see constant traffic
- Kitchen worktops and breakfast bars
- Dining tables that get used properly, not just for show
- Children's furniture and bookcases
If you've got kids, dogs, or both charging through the house at full speed, polyurethane is usually the sensible pick.
What is Lacquer Used For?
Lacquer is used for decorative indoor furniture and joinery where a smooth, glossy, professional finish matters more than raw durability. It dries incredibly quickly, often within half an hour, and builds into a gorgeously smooth sheen.
Lacquer is the finish of choice for fine furniture, musical instruments, and anything you want to look properly polished. The catch? It isn't as hardwearing as polyurethane. It doesn't love heat, alcohol, or heavy day to day use, and it's usually best applied with a spray gun for the cleanest result. That means a little more kit and a little more skill, though a careful hand with a good brush can still do a lovely job.
When to Use Lacquer
- Interior cabinets, sideboards, and display units
- Restoring vintage or antique furniture
- Decorative pieces that won't take a battering
- Skirting boards and interior mouldings
- Guitars, pianos, and crafted wooden objects
If you're restoring a 1930s walnut bureau and you want it to look the way it did the day it left the workshop, lacquer is your friend.
Which Finish is Best for Wooden Floors?
Polyurethane is the best finish for wooden floors in UK homes. It's significantly more scratch and scuff resistant than varnish or lacquer, and it handles heavy foot traffic, pet claws, and dropped pans without flinching. Water based polyurethane is usually the easiest for DIY application because it dries quickly and has a low odour.
Which Finish is Best for Outdoor Wood?
Exterior varnish, particularly yacht varnish, is the best finish for outdoor wood in the UK climate. It contains UV filters and flexible resins that cope with rain, sun, and temperature swings. Most standard polyurethane and lacquer finishes are not ideal for outdoor use, as they lack the flexibility and UV resistance of exterior varnish.
Which Finish is Best for Furniture?
It depends on the furniture and how it's used. Lacquer is best for decorative or antique pieces that won't see heavy use. Polyurethane is best for dining tables, desks, and anything that needs to handle daily life. For outdoor furniture, use exterior varnish every time.
A Few Tips Before You Open the Tin
- Sand the wood properly before you start. A pass with 120 grit, then 180, makes a huge difference.
- Wipe off every last speck of dust before applying. A tack cloth is cheap and saves a lot of grief.
- Thin coats beat thick ones every single time. Two or three light layers always outperform one gloopy one.
- Let each coat dry fully before adding the next. Rushing this stage is the number one reason finishes go wrong.
- Ventilate the room. Even the low odour products benefit from an open window or two.
- Test on an offcut first. Colours and sheen can look different once applied, so always sample before committing.
Frequently Asked Questions
Can I apply polyurethane over old varnish?
Not straight on top. The two don't always bond well, so you'll want to sand the old varnish back to give the polyurethane something to grip onto. A light key with 180 grit sandpaper is usually enough. If the old finish is flaking or damaged, strip it back to bare wood for the best results.
How many coats of varnish, polyurethane, or lacquer do I need?
Two coats can be enough for light-use surfaces, but three coats are recommended for durability. High traffic surfaces like floors, stairs, and worktops are better off with three. Outdoor projects nearly always benefit from three or four coats of varnish, with a light sand between each one to help the layers bond.
Is water based or oil based polyurethane better?
It depends what you're after. Water based polyurethane dries quickly, smells less, and stays crystal clear. Oil based polyurethane takes longer to dry but tends to be tougher and adds a warm golden tone to the wood. For floors and worktops in modern homes, water based is usually easier. For traditional timber and rich looking finishes, oil based still wins.
How long should I wait between coats?
Always follow the instructions on the tin, because formulas vary. As a rough guide: lacquer is ready in about 30 minutes, water based polyurethane in 2 to 4 hours, oil based polyurethane in 6 to 8 hours, and varnish anywhere from 8 to 24 hours. Patience here really does pay off.
Will these finishes yellow over time?
Oil based products do tend to amber slightly as they age, which some people love and others don't. Water based polyurethane and modern water based varnishes stay much clearer for longer. If you're finishing light woods like ash, maple, or pale oak and want to keep them looking natural, go water based.
Can I use interior varnish outside?
No, interior varnish shouldn't be used outside. It doesn't contain the UV filters or flexible resins needed to cope with sun, rain, and temperature changes, so it'll crack, peel, and look tired within a season. Always choose an exterior or yacht varnish for anything outdoors, even if it's under cover.
The Bottom Line
Varnish, polyurethane, and lacquer aren't interchangeable, but none of them are complicated once you know what they're actually for. Use varnish outdoors, polyurethane on hardworking indoor surfaces, and lacquer on decorative interior pieces. Prep the wood properly, apply thin coats, and take your time with drying. Whether you're reviving a tired bit of furniture or giving your hallway floor a new lease of life, the right coat is what stands between a finish you're quietly proud of and one you wish you'd done again.
Have a browse through the range at Trade Supplies UK when you're ready to get stuck in. And if you're still not certain which finish suits your project, there's no harm in asking. Most people working in the trade are more than happy to point you in the right direction, because a job done right the first time is better for everybody.
