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Grantham Damp Proofing
Condensation and mould, Grantham

Black mould is a moisture balance problem

Mould spots in bedroom corners, streaming windows on winter mornings, a black bloom behind the wardrobe on an outside wall. Condensation is the most common form of damp in Grantham homes, and the most misunderstood. It is rarely fixed by wiping walls with bleach, and it does not always mean the building is failing.

Why condensation is so common here

Condensation happens when warm, moist indoor air meets a surface cold enough for the moisture to turn back to water. Grantham's older housing gives it plenty of targets. The solid brick walls of the terraces in Spittlegate, New Somerby and Little Gonerby have no cavity to slow heat loss, so their inner faces run cold all winter. North-facing corners, window reveals, chimney breasts and the wall behind furniture are coldest of all, which is exactly where the mould appears.

Modern living makes it worse. Cooking, showers, drying laundry indoors and simply breathing put litres of water vapour into the air every day. Draught-proofing, double glazing and blocked-up chimneys, all sensible for heating bills, also remove the accidental ventilation that once carried that vapour away. The result is moist air with nowhere to go, condensing on the coldest surfaces in the house, and mould following within weeks.

Condensation or rising damp?

The two are regularly confused, and the treatments are completely different. Some useful tells:

  • Condensation favours corners, ceilings, window reveals and spots behind furniture. Rising damp forms a band low on ground-floor walls.
  • Condensation mould is typically black and speckled. Rising damp leaves tide marks and white salt deposits, and mould rarely grows on salty surfaces.
  • Condensation peaks in cold weather and eases in summer. Rising damp persists year-round.
  • Condensation appears upstairs as readily as downstairs. Rising damp cannot climb much beyond a metre.

If there is any doubt, a damp survey settles it with moisture profiling rather than guesswork.

What actually fixes it

Lasting control means changing the moisture balance of the house: less vapour produced, more vapour extracted, warmer wall surfaces. Depending on the property, the specialist may recommend:

  • Extractor fans in kitchens and bathrooms with humidity-controlled operation
  • Whole-house positive input ventilation, which gently pressurises the home with filtered air from the loft and pushes moist air out
  • Reinstating background ventilation, including trickle vents and unblocked airbricks
  • Mould treatment and stain-blocking of affected surfaces once the cause is controlled
  • Advice on heating patterns and insulation for cold solid-wall rooms
For landlords, mould is now a legal matter as well as a maintenance one. Under the Homes (Fitness for Human Habitation) Act 2018, serious damp and mould can make a rented property unfit, and Awaab's Law is extending fixed timescales for social landlords to investigate and fix reported mould. Documented diagnosis and remediation protects tenants and landlords alike.

Renting in Grantham?

Many of the terraces south of the town centre are privately let. If you rent and mould keeps returning despite normal ventilation habits, the cause may be structural, cold bridging, a failed damp proof course or leaking rainwater goods, and that is your landlord's responsibility to investigate. A survey report gives both sides an objective starting point.