How to Paint a Shed: Timber, Metal, and Plastic, Start to Finish

A shed is a whole small building, which makes it the most complete painting project most people take on at home. Roof, walls, corners, door, window, floor edge and all four elevations, all of it exposed on every side. Done properly it looks sharp and stays protected for years. Done in a rush it peels along the bottom boards within a season.

This guide is about doing the work. If you are still deciding what to put on it, the best paint for a shed post covers product selection in detail and is the better place to start that question. Here we assume you have made the call and want the method.

The short version: work out what the shed is made of and what is already on it, clean and repair everything before you open a tin, prime the bare timber and the knots, protect the roof felt and the glazing, then apply two thin coats in a decent weather window. Rough sawn timber will drink far more paint than you expect.

Assess the shed before you buy anything

Timber sheds

Most garden sheds are softwood, either overlap boards, shiplap or tongue and groove. Look at the surface finish: smooth planed timber takes paint evenly and covers at close to the stated rate, while rough sawn timber has an open fibrous face that soaks up coating and needs noticeably more material for the same area.

Metal sheds

Usually galvanised or coated steel panels. The enemy is rust, not rot, and the failure points are the fixings, the panel laps, the door track and the bottom edge where the panel meets the base. Paint sticks badly to bare galvanised metal unless you use the right primer, so this is not a job for a general timber product.

Plastic sheds, and whether to bother

Be honest about plastic. Polypropylene and polyethylene sheds are designed to shed everything, including paint. They have very low surface energy, they flex a lot in heat, and they are usually UV faded rather than dirty, which means the surface itself has degraded. You can paint one with thorough scuff sanding, a dedicated plastic or multi surface bonding primer and a flexible exterior acrylic, but adhesion is genuinely uncertain and the finish is prone to scratching off at handles, corners and the door.

PVC and uPVC clad sheds are a better prospect than polyethylene, because a proper uPVC primer will bite. Either way, test a small hidden panel first, let it cure fully, and try to pick the coating off with a fingernail before you commit to the whole building.

The substrate cases

Case 1: new or factory treated bare timber

This is the case that catches people out. Most new sheds arrive with a factory applied dip treatment or preservative, and that treatment is not a finish. It is a basic protective dip, often applied to wet timber and often still carrying solvent or water when it reaches you.

A film forming paint applied over a fresh dip treatment can fail to adhere, blister, or trap moisture in the boards. Many manufacturers specify a weathering period before you apply a film forming coating, and some specify a particular type of product. Check the manufacturer guidance that came with your shed, and follow it rather than a general rule from the internet. If the shed is brand new and you cannot find any guidance, a penetrating shed and fence treatment is the lower risk choice for the first season, with an opaque paint applied later once the timber has settled and dried out.

Genuinely bare untreated timber is simpler: it can be primed and painted straight away once it is dry and clean, but it should be treated or coated promptly because untreated softwood outdoors starts degrading quickly.

Case 2: previously painted timber

Judge the existing coating. If it is sound, well adhered and just tired, you are looking at a clean, a scuff sand, spot priming of any bare patches, and two coats. If it is cracking, flaking or peeling across large areas, you are looking at removal back to sound material, which is the real work in this job.

Check compatibility too. A film forming paint over an old penetrating stain often struggles, because the stain has left the timber surface waxy or oily. A penetrating stain over an old film forming paint will not penetrate at all, because the film is in the way. Mixing the two families is the second most common reason a shed repaint fails.

Case 3: previously stained or treated timber

If the shed has had a penetrating treatment and you want to keep going with the same family, this is the easiest case on the list. Clean it, let it dry, and recoat. No stripping, no priming, no feathering. This is the main practical advantage of penetrating finishes and it is worth weighing seriously before you commit a shed to paint.

Case 4: metal

Wire brush or abrasive pad every rust spot back to bright metal, or as close as you can get. Treat any remaining pitted rust with a rust converter or a rust inhibiting primer, and prime bare galvanised areas with a primer stated as suitable for galvanised steel. Then apply a suitable exterior metal topcoat. Do not skip the primer step on metal, because a topcoat straight onto shiny galvanised surface will sheet off.

Prep sequence

1. Clear the way

Empty the shed or at least move everything away from the walls, because you will be knocking dust and flakes off and you may want the door open for long stretches. Then clear the outside: cut back the shrub that is pressed against the back wall, move the wheelbarrow, lift anything stacked along the base. If the shed sits within a hand's width of a fence, you either move the shed or you accept you cannot paint that elevation properly. Deciding that now is better than discovering it with a loaded brush.

Sheet the ground on all four sides. Gravel and grass both hold flakes and dust, and you will be scraping.

2. Clean off green growth and mildew

The shaded side of a shed usually has a green algal film and often black mildew spots. Scrubbing alone does not kill it and it will grow through the new coating. Use an appropriate exterior cleaner or fungicidal wash, apply it, give it the stated contact time, agitate with a stiff brush and rinse. Then let the timber dry completely, which after a wash can take a couple of days in cool weather.

Be careful with a pressure washer on shed timber. Thin overlap boards are soft, and a close nozzle will raise the grain, blast out the soft spring wood and drive water deep into the boards. If you use one, keep the pressure low, keep the nozzle back, and allow much longer drying.

3. Scrape, sand and feather

Scrape everything loose. Then feather the edges of the remaining sound paint so you cannot feel a step, otherwise every old flake outline shows through the new coats. On rough sawn timber you cannot really feather, so accept more texture and focus on getting rid of anything that will lift.

4. Repair rot and replace failed boards

Probe the bottom boards, the door frame, the corners and anywhere a shrub has been resting. Small soft spots can be dug out, dried, filled with an exterior grade filler and primed. A board that is soft through its thickness should be replaced, and on a shed that is usually a straightforward job with a saw and a handful of nails. Painting over a rotten bottom board is throwing the whole day away.

While you are there, check the base. A shed sitting directly on soil or on a slab that pools water will keep rotting no matter what you paint on it. Lifting it onto bearers or improving the drainage does more for the shed's life than any coating.

5. Prime bare timber and knots

Prime every bare area, every repair and every knot. Knots in softwood bleed resin through paint and show as brown rings, so use a knotting or stain blocking product on them specifically. On bare timber, a proper exterior wood primer evens out absorption so your topcoat does not go patchy on rough sawn boards. The primer guide covers when you can skip it and when you cannot.

Protecting the parts you are not painting

Felt roof

Mineral felt is a magnet for splatter and it is almost impossible to clean once paint dries into the grit. Run a strip of masking along the eaves and drape a light dust sheet over the roof, weighted down. Do not tape aggressively to felt in hot sun, because the surface can lift when you pull the tape. Pull the tape while the paint is still slightly soft rather than the next morning.

Do not paint felt. Ordinary exterior paint on felt will crack and it can interfere with how the roof sheds water. If the felt is failing, replace it, and do that before you paint the walls so you are not walking over fresh work.

Glazing and door furniture

You have two options on the window: mask it, or cut a clean line and scrape the glass afterwards. Masking is slower to set up and faster to finish, and it is the better choice on a shed with several small panes. If you cut freehand, deliberately carry a hair of paint onto the glass so the film seals the joint between putty or bead and glass, then trim it back with a blade once dry.

Take off the handle, hasp, hinges if practical, and the number plate. Painting around door furniture always looks like painting around door furniture. If you cannot remove them, mask them properly.

Should you paint the inside?

Optional, and mostly worth it on a shed you use rather than a store. Interior boards painted a light colour make a big difference to how usable the space is, because sheds are dark. A light coloured emulsion or a general purpose interior paint is fine on the walls. If damp is an issue, avoid sealing the inside face with a heavy impermeable film, because timber walls need to be able to dry inward or outward. Ventilation matters more than coating.

Painting technique

Work with the boards, and work top down

Start at the top of a wall and work down, and paint along the length of the boards rather than across them. On overlap and shiplap cladding, first get paint into the underside lip of each board, then lay off along the face. That lip is where water sits and where an unpainted line will show as a dark stripe when the shed gets wet.

Do the door and window openings before the surrounding walls, so drips from the reveals land on unpainted cladding you will cover later. Then the corners and the trim boards. Then the field of each elevation.

Openings and edges

Paint the edges of the door itself, top and bottom included. The bottom edge of a shed door is almost always bare, and it is sitting right where water splashes up. Same for the bottom edge of the cladding and any exposed end grain on corner boards. End grain absorbs many times more water than the face, so give it extra material.

Caulk sparingly. On a shed, caulk is for gaps around the window frame and the door frame where water would get behind the cladding. Do not caulk the overlaps between boards, because cladding needs to move, and do not seal the bottom edge to the base. The caulking guide covers where sealant helps and where it causes trouble.

Coverage on rough sawn timber

Expect rough sawn boards to take substantially more paint than the container states, because the stated rate assumes a smooth surface. A fibrous open face has far more actual surface area and the first coat largely disappears into it. Buy generously for the first coat, and plan on the second coat going much further than the first. Running out of paint mid elevation and buying a new batch later is how you end up with a visible colour shift.

Sprayer or brush

A sprayer is genuinely good on a shed, because rough sawn cladding is slow and punishing to brush and a shed is small enough to mask in an hour. It gets coating into the board laps and the rough face far faster than a brush. The catch is overspray, so mask the roof, the glazing, the fence, the patio and anything downwind, and pick a still day.

On bare or rough timber, back brush after spraying. Spraying alone lays paint on top of the fibres, while a brush works it into them, and that difference shows up in how long the first coat lasts. The sprayer guide covers thinning, tip choice and technique.

Brushing is the right call for a small shed, a shed with lots of glazing, a windy site, or a shed hemmed in by things you cannot move. Use a wide brush for the field and a smaller one for the laps and reveals. Rollering is a middle option on smooth cladding but poor on rough sawn.

Choosing between paint and a penetrating finish

This is a real fork, not a detail, and it decides what your next maintenance session looks like.

Neither is better in the abstract. Paint gives a crisper look and better colour range. A penetrating finish gives you a far easier life at recoat time. Pick based on how much prep you are willing to do in a few years, and read the water based versus oil based comparison if you are choosing within the paint family.

Weather window and drying

A shed takes at least a full day and usually a weekend, so you need a run of decent weather, not one dry morning. Check the exterior painting weather guide for the temperature and humidity limits, but the practical rules for a shed are:

• The timber must be dry before you start. After rain or a wash, allow days rather than hours in cool weather.
• Avoid painting in direct hot sun on the elevation you are working on. Chase the shade around the shed instead: paint the sunny side early or late, and the shaded side while the sun is on the other face.
• Respect the recoat time on the container. Rushing the second coat over a first that has not dried through is what causes soft, sticky, slow curing finishes.
• Stop early enough that the last coat is touch dry before evening dew falls. Dew on a soft film leaves a dull, blotchy surface.

Two thin coats always beat one thick coat outdoors. The coats guide explains why, and it matters more on absorbent shed timber than almost anywhere else. How long the result lasts depends on the product type, the exposure and how well you prepped, and the exterior paint lifespan guide sets realistic expectations, though the manufacturer's own data sheet is the authority for any given product.

Safety and site setup

A shed is low, but you will still be on steps for the gable ends and the roof edge, often on soft or uneven ground. Use a stepladder with a wide base, not a chair or a stack of blocks, and never stand on the shed roof itself, which is usually thin sheet on light framing and will not carry you. Wear eye protection for overhead scraping and a suitable mask for sanding, and use the safety equipment checklist to sort your kit before you start rather than midway through.

If the shed is a very old structure with layers of original paint on a pre-1978 property, treat the old coats as possible lead until tested, and avoid dry sanding.

Sequencing the whole job

1. Clear inside and out, sheet the ground.
2. Wash off algae and mildew, then let it dry fully.
3. Scrape, sand, feather.
4. Repair rot, replace failed boards, fix the base and drainage.
5. Remove or mask door furniture, glazing and the roof felt.
6. Prime bare timber, repairs, knots and any metal.
7. Caulk the frame joints only.
8. First coat, top down, one elevation at a time, chasing the shade.
9. Wait the full recoat interval.
10. Second coat, plus edges, end grain and the bottom of the door.
11. Pull the tape while the film is still slightly soft, rehang the furniture.

If the shed sits alongside other exterior joinery you are refreshing, the exterior trim guide covers the same principles applied to fascias, casings and corner boards.

Frequently asked questions

Can I paint a brand new shed straight away?

Not always. Most new sheds arrive with a factory dip treatment or preservative that a film forming paint may not stick to, and the timber is often still damp. Check the manufacturer guidance supplied with the shed. If it specifies a weathering period before a film forming coating, follow it, or use a penetrating shed treatment for the first season instead.

How much paint does a shed need?

More than the container's stated coverage suggests if the timber is rough sawn, because an open fibrous surface has far more real surface area and the first coat sinks in. Buy generously for coat one, and expect coat two to go much further. Buy all of it in one go so the colour is consistent across the whole building.

Is it worth painting a plastic shed?

Sometimes, but adhesion is genuinely uncertain on polypropylene and polyethylene. It requires thorough scuff sanding, a bonding primer made for plastics, and a flexible exterior acrylic, and it still tends to scratch off at handles and corners. Test a hidden panel, let it cure, and try to pick it off before committing to the whole shed.

Should I use a sprayer or a brush on a shed?

Spray if the shed has rough sawn cladding, you can mask the roof and glazing, and the day is still. It is much faster into board laps. Brush if the shed is small, heavily glazed, hemmed in, or the site is windy. Either way, back brush over bare or rough timber so the coating is worked into the fibres.

Do I need to paint the inside of the shed?

No, but a light colour inside makes the space far more usable because sheds are dark. Avoid sealing the inside face with a heavy impermeable coating if damp is an issue, since the timber needs to dry in one direction or the other. Ventilation matters more than what you put on the boards.

Paint or penetrating stain for a shed?

Paint gives a solid colour and a crisper look but eventually cracks and peels, so every repaint means scraping and priming. A penetrating treatment fades instead of peeling, so you just clean and recoat. Choose based on the look you want and how much prep you are willing to do next time.