Roof Cleaning in Portsmouth

Why roofs in the Portsmouth area collect moss and algae

Portsmouth sits on a low, flat peninsula surrounded by water on three sides, so roofs here stay damp for longer after rain than they would further inland. Shaded, north-facing slopes and roofs under overhanging trees are usually the first to show green algae streaks or cushions of moss between the tiles.

Moss holds moisture against the roof covering, and in cold weather that moisture can freeze and lift tiles or slates slightly out of place. Left unchecked for long enough, moss and leaf debris can also work its way into gutters and downpipes and cause blockages well away from the roof itself.

Soft washing versus pressure washing

Most local installers use a soft-wash method on domestic roofs: a low-pressure biocide treatment that kills moss and algae at the root without disturbing the tiles, followed by a rinse. This is generally considered gentler on older or more brittle roof coverings than a high-pressure jet wash.

A pressure washer can strip moss faster, but on aged concrete tiles, slate, or clay pantiles it can also strip away the protective granule coating or force water up under the tiles. It's worth asking any installer which method they plan to use and why, particularly on an older roof.

Signs it might be time to get your roof looked at

Clumps of moss along the ridge or in the valleys, dark green or black streaking down from the ridge tiles, and gutters that fill with moss and grit faster than they used to are the usual signs. On a bungalow or single-storey extension you may be able to see this from ground level; on a two-storey house it's harder to judge accurately without getting up close.

• ■Moss cushions between tiles or along the ridge
• ■Green or black algae streaks running down the roof slope
• ■Gutters filling with moss and grit more often than before
• ■Slipped, cracked or lifted tiles near patches of moss

What to ask when you're comparing quotes

Because roof cleaning covers everything from a straightforward soft wash to scaffolding-assisted work on a steep Victorian roof, it's worth asking each installer to look at the actual roof before pricing the job. What affects the price is usually the size and pitch of the roof, how many storeys it sits at, how much access equipment is needed, and how much moss and lichen has built up.

Ask what method they use, whether they'll clear the gutters as part of the job or as an extra, and what access equipment they bring — a ladder is fine for a single-storey roof, but a two- or three-storey house usually needs a tower or scaffold. The Health and Safety Executive publishes guidance on the precautions expected for any work at height, which is a reasonable thing to ask an installer about. Get more than one written quote before deciding.

Roofs on older or listed homes

Portsmouth and the towns around it have pockets of older housing — Georgian terraces near the seafront, Victorian streets further back from the water, and a number of listed buildings and conservation areas dotted through Gosport, Fareham, Havant and the villages further out. If your home is listed or sits in a conservation area, it's worth checking with the relevant council before any work that goes beyond a straightforward clean, since some works to the roof covering itself can need consent even where a simple wash wouldn't.