Is linseed oil paint better than modern exterior paint on old windows?

It behaves differently rather than simply being better. Linseed oil paint is designed around regular light maintenance instead of infrequent complete repaints, and it tends to weather thin rather than crack and peel. Owners of period properties often return to it after modern coatings have failed early on exposed elevations.

Period property guide

Preparing and painting timber windows on a period property.

Q: Should gaps around old timber windows be filled or left open?

Not every gap should be filled. A gap that lets a wet joint dry out is doing useful work, and bridging it with paint alone tends to crack and then trap water behind the film. Where a gap genuinely needs closing for weathertightness, a flexible material that moves with the timber is the right choice, not a rigid filler.

Q: Can I use expanding foam around a period window?

No. Expanding foam holds moisture against the timber rather than excluding it, and it cannot move with seasonal timber movement. On older windows it is a common cause of rot appearing a few years later, and removing it is usually part of putting the window right.

Most repainted timber windows fail in the same few places for the same few reasons. Understanding why changes what you do before the first coat goes anywhere near them.

The uncomfortable truth

Aspect matters more than what is on the tin.

Owners comparing notes on period properties describe the same pattern again and again: the same paint, applied on the same day by the same person, lasting fifteen years on a shaded north elevation and failing within two or three years on a south-facing sill of the same house. One owner reported a modern water-based exterior paint cracking and peeling within two years on south-facing sills, while black paint on a permanently shaded north elevation stayed close to perfect for over fifteen.

South and west elevations take the sun, the heat cycling and the driving rain. Sills take all of that and are horizontal, so water sits on them rather than running off. If your paint is failing on the sills and cills first, that is not necessarily a fault in the product or the preparation — it is where the weather is.

The practical consequence: budget your maintenance by elevation, not by the whole house. The south side will need attention long before the north side does, and treating them as one job on one cycle wastes money on one and neglects the other.

Two different philosophies

Linseed oil paint expects maintenance. Modern paint expects to be left alone.

This is the real difference, and it is not really about which product is better. Modern exterior systems aim to form a tough, impermeable film that is left untouched for years. When that film fails on an exposed elevation, it fails by cracking and peeling, and water gets behind it — which is worse for the timber than no coating at all.

Linseed oil paint is built around the opposite assumption. It weathers thin rather than cracking, and it is designed to be topped up regularly and lightly. Owners report linseed oil on exposed oak still sound after fifteen years without being touched, and many go back to it after a modern coating has failed early.

Neither approach is wrong. But choosing a modern film and then treating it as maintenance-free on a south-facing sill is how people end up stripping back to bare wood after three years. Decide which model you are signing up to before choosing the paint.

Source and further discussion: Painting timber windows — a verdict and a question on the Period Property forum.

The most common mistake

Not every gap should be filled.

The instinct on seeing a gap between a casement and its frame is to close it. Often that is exactly wrong. A gap that allows a damp joint to dry out is doing useful work, and the usual approach — running paint across it — creates a thin bridge that cracks with the first season of movement and then holds water behind it.

Where a gap does need closing for weathertightness, the material has to move with the timber. Rigid fillers and hard putty crack as the frame swells and shrinks through the year. Flexible frame sealants, burnt sand mastic and traditional linseed putty all accommodate that movement instead of fighting it.

Expanding foam is the one to avoid completely. It holds moisture against the timber rather than excluding it, cannot move with the frame, and is a common cause of rot appearing a few years later. Finding and removing it is often the first stage of putting an old window right.

Doing it properly

The preparation that decides how long it lasts.

Assess by elevation first

Walk each side separately. South and west sills will be in the worst condition and need the most work; a shaded elevation may need very little. One survey, four different answers.

Back deep gaps before filling

A deep void will not hold filler on its own. It needs packing first — caulking cotton or a foam backer rod — to give the filler something to bear against, then finishing on top.

Repair rot, don't bury it

Filler over soft timber fails and hides the problem while it spreads. Cut back to sound wood first, even where that turns a decorating job into a repair job.

Match the maintenance to the aspect

Plan to revisit the exposed elevations on a shorter cycle. Light, regular attention on the south side is far cheaper than a full strip and rebuild every few years.

Before you start

Where consent comes into it.

On a listed building the distinction that matters is repair against replacement. Babergh District Council's listed-building guidance is that replacing windows and doors needs listed building consent, while limited repairs may not, provided they use matching materials and traditional methods. Repainting in the same colour is generally treated as work that does not need consent; changing the colour, or changing the type of coating, is more likely to.

There is a real local example of this in Glemsford. Skates Hill House, a Grade II listed 17th-century timber-framed house, was the subject of listed building consent application DC/26/01145 covering removal of modern paint products from painted brickwork along with sash window and timber-frame repairs — repair-led work on exactly this kind of window, going through consent.

Worth knowing separately: Babergh and Mid Suffolk operate a Local Listed Building Consent Order that grants blanket consent for secondary and double glazing on Grade II listed buildings subject to conditions. It covers glazing rather than repair or redecoration, and does not apply to Grade I or Grade II* buildings, but it is useful to know about if secondary glazing is part of your thinking.

Our planning permission guide covers the consent question in more detail.

Timber windows FAQ

Common questions before starting.

Why does paint keep failing on my window sills but not elsewhere?

Almost always aspect and standing water. South and west-facing sills take the most sun, heat and driving rain, and being horizontal they hold water rather than shedding it. The same paint on a shaded north elevation of the same house can last many times longer.

Should gaps around old timber windows be filled or left open?

Not all of them. A gap that lets a wet joint dry out is doing useful work, and bridging it with paint tends to crack and trap water behind the film. Where a gap genuinely needs closing, use something flexible that moves with the timber, not a rigid filler.

Can I use expanding foam around a period window?

No. It holds moisture against the timber rather than excluding it and cannot move with the frame. On older windows it is a common cause of rot appearing a few years later.

Do I need listed building consent to repaint timber windows?

Repainting in the same colour is generally treated as work that does not need consent. Babergh's guidance is that replacing windows and doors needs listed building consent, while limited repairs may not if they use matching materials and traditional methods. Changing colour or coating type is more likely to need consent.

Is linseed oil paint better than modern exterior paint?

It behaves differently rather than being simply better. It is designed around regular light maintenance instead of infrequent complete repaints, and weathers thin rather than cracking and peeling. Many owners return to it after a modern coating has failed early on an exposed elevation.

The rest of the exterior decision.

Timber windows are one part of a wider exterior. See removing non-breathable paint, limewash vs silicate paint and choosing authentic period colours, or browse all the period property guides.

Timber windows needing attention?

Happy to look before anything gets stripped.

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