Dry rot, wet rot and woodworm in Renfrewshire

Renfrewshire is the part of the West team’s patch where the weather does most of the work. The county sits between the Clyde estuary and the Gleniffer Braes with very little between it and the open water, and the prevailing wind brings rain in from the south west almost horizontally. That is a meaningfully different problem from rain falling on a roof. It is driven into the vertical face of a wall and held there, and a wall that is wet for weeks at a time is a wall whose timber cannot dry.

The building stock then divides fairly sharply. There is the dense pre-1919 tenement and terrace ofPaisley, Renfrew and Johnstone, which behaves much like Glasgow. There is the post-war expansion at Linwood, Erskine and the edges of Paisley. And there is the older, more spread out property of Bridge of Weir, Kilmacolm, Houston and Lochwinnoch, which is a different job again.

The one wall that takes everything

If you take one thing from this page, take this. In Renfrewshire, damp and rot are frequently confined to a single elevation of the building, and it is usually the one facing south west. People find that hard to believe, because a wet patch inside a room feels like it ought to have an internal cause. It often does not.

Solid stone and rendered walls handle driven rain by absorbing some of it and letting it dry out again between wettings. That works while the wetting is occasional. On an exposed gable through a west of Scotland winter the wall does not get a dry spell long enough, so the moisture front works steadily inward. Where a joist end, a wall plate or a strapped and lined internal finish sits against that face, the timber stays damp for months. Wet rot follows, and if the timber is enclosed and unventilated, dry rot can follow instead.

Cracked or blown harling makes this dramatically worse, because water gets behind the render and then cannot evaporate back out through it. A hairline crack that looks like nothing can keep a square metre of wall saturated all winter.

What we find where

The tenement and terrace core

Paisley’s older streets, central Renfrew and Johnstone. Solid sandstone, shared closes, shared rainwater goods, joists into the wall. The failure mode is the classic one and thedry rot page for the West covers it properly. What Renfrewshire adds is exposure: the same building here gets a harder time from the weather than its equivalent in the east end of Glasgow, so the same defect produces a bigger problem sooner.

Mill and industrial conversions

Paisley’s thread mills and the smaller works around them have been converted to flats over the last thirty years, and these buildings are their own category. Enormous original timbers, often with historic beetle damage in them, boxed into modern insulated construction. Two questions come up every time: is the old woodworm damage active or finished, and is the new construction holding moisture against timber that used to be able to breathe. Both are answerable on a survey and neither is answerable by looking at the surface of a beam.

Post-war and later housing

Linwood, Erskine, Foxbar, Glenburn and the newer edges of most towns. Cavity walls, suspended timber ground floors on the earlier stock, concrete floors on the later. The recurring finding is blocked underfloor ventilation, and in Erskine and Bishopton specifically we see a lot of it caused by ground levels being raised in later landscaping until the airbricks are at or below soil level.

Villas and older detached property

Kilmacolm, Bridge of Weir, Houston, Lochwinnoch and the better streets of Paisley. Larger buildings, often with bay windows, dormers, timber sash and case windows and complicated roofs. More junctions means more places for water to get in, and these are the properties where the decay is most likely to be somewhere nobody has looked: a dormer cheek, a bay roof, the base of a sash box, or the timber lintel over a window.

What the survey is actually looking for

On a Renfrewshire job, more of the answer is outdoors than people expect. A surveyor here will want to see the state of the render on the weather elevation, whether the rainwater goods are actually carrying water or spilling it down the wall, whether ground levels have crept up the outside of the building, and where the water lands when it leaves the downpipe. The internal work then confirms how far it has got: lifting a small number of floorboards in the right places, getting into the void, and checking the joist ends built into the wall that has been wet.

That order matters because treating timber without fixing the wall that is wetting it buys you a few years at most. Any quote that proposes the second without addressing the first is worth asking hard questions about, whoever it comes from.

Where we go in Renfrewshire

Paisley, Renfrew, Johnstone, Linwood, Elderslie, Erskine, Bishopton, Houston, Bridge of Weir, Kilmacolm, Lochwinnoch, Barrhead and Neilston, plus Port Glasgow, Greenock and Gourock down the coast. The postcode is the reliable boundary: PA1 to PA19 is inside the patch. Anything from PA20 upward is Argyll, Bute or the islands, and that is not a run this team can make.

Paisley has its own page, because it is far and away the largest concentration of older property in the county and the shared repair questions there are different from anywhere else in Renfrewshire. The West of Scotland page covers the rest of the region.