Damp has many causes and they are easy to confuse. A patch on a chimney breast might be penetrating rain, condensation, hygroscopic salts from decades of coal fires, or a roof fault three metres higher. A proper survey works out which, so you only pay to fix the problem you actually have.
Grantham's housing spans almost every construction era: medieval and Georgian limestone in the conservation area around St Wulfram's and Castlegate, dense Victorian and Edwardian brick terraces south and east of the centre, interwar council-built semis on the Harrowby estate, begun in 1928, and at Earlesfield, and modern estates such as those on Gonerby Hill. Each era fails differently. A moisture reading that means one thing in a cavity-walled 1930s semi means something quite different in a solid limestone wall bedded in lime mortar.
The town's setting adds its own complications. The lower streets sit on slow-draining mudstone close to the River Witham, so ground moisture stays high through winter, while the culverted Mowbeck passes behind Westgate and Brook Street. Against that background, jumping straight to an injection quote without diagnosis is how homeowners end up paying twice.
Three groups, mostly. Homeowners who have noticed a symptom and want to know how serious it is. Buyers whose mortgage valuation or building survey has flagged "dampness" in a Grantham property, often one of the older terraces, and who need a specialist opinion and a cost before exchange. And landlords, who since the Homes (Fitness for Human Habitation) Act 2018 have a legal duty to keep rented homes free of serious damp and mould hazards, and need documented evidence that a problem has been investigated and dealt with.
The survey report is yours either way. If treatment is recommended, the quote itemises the work so you can see exactly what you are paying for. If the fix is simple maintenance, clearing a gutter, lowering a flower bed, unblocking an airbrick, the report says that instead. The specialist quotes for work the evidence supports.