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Grantham Damp Proofing
Rising damp treatment, Grantham

Rising damp in Grantham's older homes

Tide marks a metre up the wall, blistering paint, a white salt crust on the plaster. In a town with this many pre-1919 solid-wall houses, genuine rising damp is a familiar problem, and it is also one of the most misdiagnosed. The right response starts with finding out whether moisture really is climbing from the ground.

Why Grantham's terraces are prone to it

The streets that grew around Grantham's Victorian engineering works, in Spittlegate, New Somerby and Little Gonerby, were built in solid brick, two courses thick, sitting close to a water table fed by the River Witham and the culverted Mowbeck. Many were given a slate damp proof course when built; some were not. After more than a century, slates crack, mortar beds erode, and external ground levels creep upwards with each new path or patio until they bridge the original barrier.

Because the valley-floor ground below much of the town is clay and mudstone rather than free-draining limestone, moisture lingers around footings long after rain. Ground salts, mainly chlorides and nitrates, travel up the brickwork with that moisture and are left behind in the plaster as the wall dries. Those salts are hygroscopic, meaning they pull moisture out of the air, which is why a wall with an old rising damp problem can feel damp even in dry weather, and why replastering with the wrong materials fails within a year or two.

What genuine rising damp looks like

  • A horizontal tide mark, typically up to about a metre above floor level, on ground-floor walls
  • White, fluffy salt deposits on plaster or brick, often reappearing after redecoration
  • Peeling wallpaper and blown or crumbly plaster low on the wall
  • Skirting boards that feel damp, stain or begin to rot from the back
  • A persistent musty smell in ground-floor rooms

Several other faults mimic these symptoms, including leaking gutters, raised external ground, condensation behind furniture and plumbing leaks. Treating a wall for rising damp when the actual fault is a cracked downpipe wastes money, which is why the specialist begins with a diagnosis rather than a sales pitch. If the cause is something simpler, they will say so.

How treatment works

Where rising damp is confirmed, treatment normally involves two stages. First, a new damp proof course is installed, most commonly by injecting a silicone-based cream into a drilled mortar bed so it cures into a water-repellent barrier. Second, salt-contaminated plaster is removed and the wall is replastered with a renovating system that holds back residual salts while the masonry dries out, a process that can take months in a thick solid wall.

In the conservation area around St Wulfram's, and in limestone buildings generally, the approach changes. Lime-built walls need breathable materials, and hard cement renders or gypsum skim coats are usually the wrong answer. The specialist will recommend an approach that suits the age and construction of the building, not a one-size treatment.

Ground levels matter as much as chemistry. A surprising number of Grantham damp problems trace back to a garden path, drive or flower bed built up above the damp proof course line. Sometimes lowering the ground or cutting a drainage channel solves the problem with no injection needed at all.

What it costs

Costs depend on wall length, wall thickness and how much replastering is needed, so a fixed national price list would be misleading. After the survey you receive a written quote covering the damp proof course, plaster renewal and any related work such as skirting replacement, with no obligation to proceed.