Penetrating damp in Boston homes
The fens are flat, and Boston's weather arrives sideways. Rain driven across open farmland from The Wash finds every weak point in a wall, and a solid brick wall has no cavity to stop it once it is through the outer face.
Penetrating damp is water getting through the fabric of the building: through porous brick, failed mortar joints, cracked render, leaking gutters, or a chimney stack that has lost its flaunching. Unlike rising damp it can appear at any height, and unlike condensation it tracks the weather. If a patch darkens during rain and fades over a dry week, penetrating damp is the likely cause.
Boston's older housing is particularly exposed to it. Much of the stock around the town centre is Victorian or older, built in solid brickwork that relies entirely on the condition of its outer face. A century and a half of fenland weather, plus decades of patch repairs in hard cement mortar that traps moisture, leaves many walls taking in more water than they can shed. On the post-war estates the usual suspects are simpler: blocked or sagging gutters, cracked renders and worn sealant around windows.
Where it usually gets in
| Entry point | What you see inside |
|---|---|
| Eroded mortar joints on exposed gables | Broad damp patches on upstairs walls after wind-driven rain |
| Chimney stacks and flashings | Damp chimney breasts, stains spreading across ceilings |
| Blocked, split or sagging gutters | A vertical damp streak on one wall, green algae outside |
| Cracked render or spalled brick faces | Isolated patches that darken in wet weather |
| Perished window and door seals | Damp reveals, swollen sills, draughts with the damp |
How the specialist approaches it
- Trace the source. The damp patch inside rarely sits directly behind the defect outside. The inspection follows the water back to where it enters.
- Fix the defect. Repointing in an appropriate mortar, gutter and downpipe repairs, chimney work, render repairs, or resealing around openings.
- Let the wall dry, then make good. A solid wall that has been wet for months holds a surprising amount of water. Redecorating too early wastes the redecoration.
- Protect exposed elevations where justified. On hard-weathered gables a breathable water repellent can help, but only on sound, well-pointed brickwork.
Old walls need breathable repairs
Many Boston walls were built in soft brick and lime mortar. Repairing them with hard cement or sealing them with impermeable paint tends to make penetrating damp worse, because water that gets in can no longer get out. In the conservation streets around the Market Place and the riverside this matters for planning as well as physics. The specialist matches materials to the wall rather than defaulting to the cheapest repair.
Not sure whether your problem is penetrating damp, rising damp or condensation. A survey settles it with readings rather than guesswork.
Damp patch that comes and goes with the rain
Send a description or call. The specialist covers Boston, Kirton, Wyberton and Swineshead and quotes after seeing the wall.
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