White streaks on fascia boards usually have one of two causes: dirty water repeatedly overflowing from blocked gutters, which leaves striped staining known as “tiger striping”, or the surface of uPVC boards slowly oxidising into a chalky white powder. Both look similar from the pavement, but they tell you different things about your roofline — and both are fixable.

In this guide, we’ll explain how to tell the two apart, what each one signals about the health of your gutters and fascias, and how professional cleaning deals with them.

Cause 1: Tiger Striping from Overflowing Gutters

The most common culprit is your guttering. When gutters fill with leaves, moss, and silt, rainwater can no longer flow along the channel to the downpipe. Instead, it spills over the front edge — and it doesn’t spill cleanly.

That overflowing water carries dissolved dirt, organic matter, and grime from inside the gutter. As it dribbles down the fascia in the same places time after time, it leaves vertical streaks of staining. Because the streaks alternate with cleaner sections of board, the pattern resembles stripes — hence the trade nickname “tiger striping”.

What tiger striping tells you

Tiger striping is a diagnosis as much as a stain. If your fascias are striped, your gutters have been overflowing regularly, and probably for some time. Therefore, the staining is rarely the whole problem. The same overflow that marked the boards has also been running down your walls, and prolonged overflow is one of the classic early steps towards penetrating damp. Our article on the warning signs your gutters need cleaning covers where that road leads if it’s ignored.

In short: tiger striping means book a gutter clean, not just a fascia wash. Cleaning the boards without clearing the gutters guarantees the stripes come straight back.

Cause 2: Chalky Oxidation on uPVC Boards

The second cause has nothing to do with gutters. uPVC fascia boards are exposed to sunlight and weather every day of their lives. Over many years, the surface layer of the plastic can slowly degrade and oxidise. The result is a dull, faded appearance and a fine white chalky residue — if you rub a finger across the board, it comes away powdery.

Oxidation is a surface condition rather than structural damage. However, it does indicate the board’s original finish is ageing, and heavily oxidised boards stain more easily because the degraded surface is more porous. Regular cleaning slows the process down by removing the dirt and organic growth that accelerate surface wear.

Telling the two apart

A quick way to distinguish them:

Tiger striping appears as distinct vertical streaks, concentrated below the gutter line, often grey-green or brown-tinged rather than pure white.
Oxidation is an even, all-over chalkiness across the whole board face, with powder that rubs off on your finger.

Many rooflines in West London show both at once, especially where gutters have been neglected for a few years. Consequently, a proper inspection looks at the gutters and the boards together.

What About White Residue Dripping from the Gutter Itself?

Occasionally homeowners notice a white or milky residue appearing at gutter joints rather than on the board face. This is usually connected to the same underlying issue — standing water sitting in a blocked or poorly draining gutter, mixing with debris and leaching out at the seams. Either way, the message is the same: the gutter needs clearing and the joints need checking.

How Cleaning Fixes White Streaks

The right fix depends on the cause, which is why we always start with an inspection.

Step 1: Clear the gutters

If tiger striping is present, the gutters get cleared first. There’s no point washing the boards while the source of the staining is still overflowing above them. Clearing the channel and checking the downpipes stops the streaks recurring.

Step 2: Clean the boards

A professional fascia and soffit clean then removes the staining, algae, and mould from the board surfaces, along with the chalky oxidation layer on uPVC. We use techniques appropriate to the material, so painted timber and uPVC are both treated without damage. Soffit vents are cleared at the same time.

Step 3: Inspect for underlying damage

Finally, the boards and gutter fixings are inspected. Long-term overflow can soften timber fascias and loosen brackets, so we check for rot, gaps, and sagging while we’re up there. Additionally, you receive before-and-after photos with every job, so you can see the difference — and the condition of your roofline — without leaving the ground.

If the inspection turns up damage, we provide a free written quote for repairs, which carry a 12-month workmanship guarantee. For most homes in areas like Uxbridge and Hillingdon, though, a thorough clean is all that’s needed.

How to Keep the Streaks from Coming Back

Prevention is mostly about the gutters. Keep them cleared regularly — at least annually, or more often under heavy tree cover — and overflow staining simply doesn’t get the chance to develop. For the boards themselves, a professional fascia and soffit clean every 2–3 years keeps organic growth and surface dirt from building up.

Frequently Asked Questions

What are the white streaks on my fascia boards?

They’re usually either “tiger striping” — staining left by dirty water overflowing from blocked gutters — or chalky oxidation on ageing uPVC boards. Striping is streaky and concentrated below the gutter line, whereas oxidation is an even chalkiness across the whole board.

Will cleaning remove tiger striping?

Yes, in the vast majority of cases professional cleaning removes the staining. Crucially, the gutters must be cleared at the same time, because striping returns quickly if the overflow that caused it continues.

Is chalky white powder on uPVC fascias serious?

It isn’t structural damage, but it shows the surface finish is ageing. Regular cleaning removes the residue and slows further surface wear by keeping dirt and organic growth off the boards.

Do white streaks mean my gutters are blocked?

Very often, yes. Tiger striping only forms when water repeatedly overflows the gutter edge, so it’s a reliable sign the gutters need clearing and inspecting.

Spotted streaks on your roofline? We clean fascias, soffits, and gutters across Uxbridge, Harrow, Hayes, Hillingdon, Slough, Southall, West Drayton, and Windsor — with before-and-after photos on every job. Request a free quote form and we’ll respond within 2 hours during business hours, with same-week appointments available.

White Streaks on Fascia Boards Explained