Painting a garage is really three jobs in one. There is a concrete floor, walls of bare block or brick, and a door that could be steel, timber or GRP. Each surface fails in its own way when the preparation is wrong.
This guide works through all three, from testing a new slab for moisture to priming a galvanised door. It draws on the surface preparation behind every garage we paint across Greater Manchester.
In short
- A new concrete floor must cure and then dry out before painting, which often takes months.
- A taped plastic-sheet test is a quick moisture check, but epoxy makers usually specify a measured limit.
- Oil stains are degreased and weak laitance is ground or etched away, or the coating will lift.
- Two-part epoxy resists hot-tyre pickup and oil far better than single-pack floor paint.
- Bare block walls are brushed down, stabilised if chalky, then finished in masonry paint.
- Galvanised steel needs a primer made for galvanised metal, because ordinary oil-based primers can peel.
Painting a garage floor starts with the concrete
Most garage painting problems start on the floor. The coating itself is rarely at fault. Instead, the slab underneath is too wet, too weak on the surface or too contaminated with oil.
Curing and drying are not the same thing
Curing is the chemical reaction that gives concrete its strength. The usual benchmark is 28 days, and many floor coating makers give that as a minimum age.
Drying is separate, and much slower. A slab can be fully strong and still hold a lot of water. A rule of thumb often quoted for screeds is about a day per millimetre for the first 40mm, slowing down after that. A thick slab in a cold, shut-up garage can take months.
Coat a wet slab and moisture pushes up behind the film. The coating blisters, loses its grip and peels, sometimes within months.
How to test a concrete floor for moisture
A simple check is worth doing on any garage floor, new or old:
- Tape a square of clear polythene, roughly 450mm across, flat to the floor.
- Seal all four edges with duct tape so no air can get in.
- Leave it for at least 16 hours, ideally a full day.
- Lift it and look. Condensation under the sheet, or darker concrete, means moisture is still coming through.
This is a rough indicator, not a measurement. For two-part epoxy, the manufacturer usually states a maximum moisture level, measured with a hygrometer. That figure is the one that counts.
Older slabs often have no damp-proof membrane, so an old floor can fail the test too.
Preparing a concrete floor for painting
Once the slab is dry, the surface is prepared. This is the hard, dusty part, and it decides whether the coating lasts.
- Oil and grease are scrubbed out with a concrete degreaser, rinsed and treated again. Deep stains can keep wicking back, so they are rechecked before coating.
- Laitance, the weak, powdery skin on new concrete, is removed by diamond grinding or shot-blasting, or by acid etching on smaller floors.
- Power-floated slabs are very smooth and dense, so they normally need grinding to open the surface.
- Old coatings that flake or lift with tape are removed, and sound ones are keyed.
- Cracks and pits are filled with a compatible concrete repair product.
A water test tells you a lot. Sprinkle a little water on the floor. If it soaks in and darkens the concrete, the surface is open. If it beads, a sealer, oil or a dense, glassy surface is in the way.
Etching puts water back into the slab. Therefore an etched floor is rinsed thoroughly, neutralised if the product requires it, and left to dry again.
Garage floor paint vs two-part epoxy
Single-pack floor paint comes ready to use. It dries as the water or solvent evaporates, and some types harden further in air. It is easy to apply and easy to refresh. For a workshop, gym or storage garage with light foot traffic, it is often enough.
Two-part epoxy works differently. A resin and a hardener are mixed, and they cure by chemical reaction into a much harder film. It resists oil, fuel and abrasion far better. However, it has a limited pot life once mixed, and it is fussier about moisture and temperature.
Watch the labels. Some single-pack tins say “epoxy” on the front. These are usually epoxy-modified or epoxy ester paints that dry in air. A true epoxy comes as two components that must be mixed.
| Feature | Single-pack floor paint | Two-part epoxy |
|---|---|---|
| How it hardens | Dries in air | Chemical reaction between resin and hardener |
| Application | Straight from the tin | Mixed in batches, with limited working time |
| Hot-tyre resistance | Prone to pickup | Much better, if the preparation is right |
| Oil and fuel resistance | Moderate | High |
| Moisture in the slab | Needs a dry slab | Needs a dry slab within the maker’s stated limit |
| Sunlight | Varies by product | Many yellow in strong sunlight |
| Repairs and recoating | Easy to refresh | Needs abrading first; patches can show |
| Best for | Storage, workshops, light use | Parked cars and heavier use |
Hot-tyre pickup and cure times
Tyres get hot on a drive, and that heat can soften a floor coating. When the car moves off, the tyre can lift the paint in patches. That is hot-tyre pickup, and it is the classic failure of single-pack paint in a garage.
Epoxy resists it far better, but only when fully cured and bonded to sound concrete. Manufacturers give separate times for foot traffic and vehicles. The vehicle time is usually days rather than hours.
Cold slows everything down. In a chilly, damp garage, epoxy cures slowly and can develop a greasy surface film called amine blush. Therefore epoxy floors are best laid when the garage stays above the maker’s minimum temperature, day and night.
Anti-slip additive
Gloss epoxy is slippery when wet, and cars bring in plenty of Manchester rain. An anti-slip aggregate, mixed into or scattered over the final coat, adds grip. The trade-off is a floor that is slightly harder to sweep. Near the door and on any slope, it is worth having.
Painting garage walls: bare block and brick
Most garage walls are bare concrete block or common brick. They are porous, dusty and sometimes damp, especially single-skin walls on detached garages. Emulsion on bare, dusty block tends to powder and flake.
The walls are brushed down hard to remove dust, cobwebs and loose mortar. White salt deposits are brushed off dry rather than washed, since washing just dissolves them back into the wall. If the surface is still chalky, a stabilising primer such as Dulux Trade Weathershield Stabilising Primer is applied to bind it.
A smooth masonry paint, such as Sandtex Trade or Johnstone’s Trade Stormshield, then works well indoors as well as out. It is tough, breathable and forgiving on uneven block. Bare block drinks paint, so the first coat is often thinned as the manufacturer allows.
It goes on with a long-pile roller, with a brush worked into the joints. If a wall is actively damp, paint will not solve it. The cause is found first, whether that is a blocked gutter, failed pointing or soil banked against the wall.
Integral garages and fire doors
In an integral garage, the door into the house is usually a fire door, particularly on newer homes. It can be painted like any interior door. However, never paint over the intumescent strips and smoke seals around its edges. Paint can stop them working in a fire.
Painting a garage door: steel, timber or GRP
On larger detached homes in Bramhall, a double garage door can be the widest single surface on the frontage. Garage doors are part of our exterior painting work, and the right system depends on the material.
Galvanised steel doors
Most steel up-and-over and sectional doors are galvanised, with a factory paint finish over the zinc. That finish is cleaned, degreased and lightly keyed. It is then painted with a system the paint maker lists for pre-coated metal.
Bare galvanising is the tricky part. New zinc is smooth, and it reacts with oil-based alkyd paints, which then peel away in sheets. Therefore bare zinc gets a primer made for galvanised steel, such as an etch primer or Hammerite Special Metals Primer. Red oxide and other ordinary oil-based primers are not suitable.
Rust spots are sanded or wire-brushed back to bright metal and spot-primed before the full coat. Springs, cables, tracks and seals are left unpainted. Roller doors are a special case, because the slats flex as they roll, so check with the manufacturer before painting one.
Timber garage doors
A timber garage door is exterior joinery, so it is treated like any other. It is sanded and knotted, then either primed and painted in exterior gloss or satin, or finished in a microporous stain. The bottom rail and lower edges rot first, so they get the most attention.
The method is the same as in our guide to painting a front door. If old paint keeps flaking, the causes often mirror those in our post on why fence paint is not sticking. Timing matters too, so plan around the best time of year to paint a house exterior.
GRP garage doors
GRP doors are moulded glass-reinforced plastic, often with a wood-grain texture. They are washed, degreased and lightly keyed with a fine abrasive pad, without cutting through the surface. An adhesion primer that its maker lists for GRP goes on before the topcoat. As with composite front doors, check the door’s guarantee before painting.
Converted garages: it becomes interior painting
Once a garage becomes a home office, gym or bedroom, it stops being a garage for painting purposes. New plasterboard and skim need a mist coat, then emulsion, like any fresh plaster. This falls under our interior painting service, and it is work we often see on extensions and renovations around Standish.
Fitted cupboards and utility units can be spray-finished too, using the same process as our kitchen cabinet spraying in Timperley.
Where we draw the line
We will not paint a new concrete floor before it has cured and dried out. It is a request we hear, usually because the car needs to go back in. However, coating a wet slab traps moisture under the film.
The coating then blisters and peels. Worse, the failed layer has to be ground off before anything else can go on. So we test first and wait if we have to. If the slab needs more time, we can paint the walls and door now and come back for the floor.
Painting a garage yourself is realistic on the walls, and on an old, dry floor with single-pack paint. Grinding laitance and laying epoxy are harder, and a failed floor is slow to put right. For heavy-duty industrial resin flooring, a specialist flooring contractor is the right call.
Get a free quote in Manchester
We will look at your garage first, then tell you honestly what the floor, walls or door need. We cover the whole of Greater Manchester from Cheadle. Our Manchester house painters page lists the areas we work in.
Cost depends on the size and condition of the garage. Quotes are free and no-obligation. Contact us online or call 07835 733353.
Frequently asked questions
How long should new concrete cure before you paint it?
Concrete gains most of its strength in about 28 days, and many coating makers give that as a minimum age. However, it also has to be dry, which takes longer. A common rule of thumb for screeds is roughly a day per millimetre for the first 40mm, and a full slab can take months. Test for moisture before coating.
What is the best paint for a garage floor?
For light use, such as storage or a workshop, a good single-pack floor paint is often enough. If you park a car on the floor, a two-part epoxy is far more resistant to hot tyres, oil and wear. Either way, the result depends more on a dry, clean, properly prepared slab than on the product itself.
Why is my garage floor paint peeling?
The usual causes are moisture rising through the slab, oil contamination, a weak surface layer called laitance, or hot tyres lifting a single-pack paint. Peeling in the tyre tracks points to hot-tyre pickup, while blistering and widespread lifting suggest damp. The cause has to be dealt with, and the failed coating removed, before the floor is recoated.
Do you need to etch a concrete floor before painting?
New or very smooth concrete needs its weak surface layer, called laitance, removed so the coating can grip. Grinding or shot-blasting is the most reliable method. Acid etching can work on smaller floors, but the slab must be rinsed well and left to dry again. A simple water droplet test shows whether the surface is open enough.
Can you paint breeze block walls in a garage?
Yes. Brush the blocks down to remove dust and loose material, stabilise any chalky surface, then apply a smooth masonry paint with a long-pile roller, working it into the joints. Bare block is very absorbent, so the first coat may be thinned as the manufacturer allows. A wall that is actively damp needs the cause fixed first.
What primer do you use on a galvanised garage door?
Use a primer made for galvanised or non-ferrous metal, such as an etch primer or a special metals primer. Ordinary oil-based primers, including red oxide, can react with the zinc and peel. Most steel garage doors already have a factory finish, which is cleaned, degreased and keyed before repainting, with any bare spots primed separately.
