Foundation Waterproofing near you

The most common damp fault in a British house is not a failed damp-proof course but a bypassed one. A new patio, a path, a raised bed or a gravel border built up above the line of the damp-proof course lets moisture cross it, and the wall inside goes damp in a building whose original detailing was perfectly sound. Approved Document C's figure of at least 150mm above the adjoining ground exists precisely to leave that margin, and a great deal of remedial damp work in this country is really landscaping in disguise.

Render and external insulation can do the same thing when they are carried down past the damp-proof course, giving moisture a continuous path around it. Inside, a solid floor screed laid over the top of a wall's damp-proof course, or a plaster coat continued down to the floor, can bridge the same barrier from the other side. None of this is cured by injecting a new chemical course into the wall, because the original was not the thing that failed.

Before agreeing to any injected or applied system, ask the surveyor to walk the outside of the house with you and show you where the damp-proof course is, what the ground level is doing relative to it, and whether anything is carried across it. Ask also about the drains and gullies nearby, since a leaking gully beside a wall produces damp that looks exactly like rising damp and responds to none of the usual treatments.

The Approved Documents are guidance for England. Approved Document C is described by GOV.UK as building regulation in England for the condition of the ground upon which a building is to be built, and its current edition covers the clearance or treatment of unsuitable material, resistance to contaminants and sub-soil drainage, with information on the resistance to moisture of floors, walls and roofs and examples of damp proofing and ventilation provisions. Approved Document A is likewise building regulation in England, covering the loadings on a building and the construction of the structural elements including the foundations.

Scotland runs a separate system. The Scottish Government publishes the building standards technical handbook for domestic buildings, which provides guidance on achieving the standards set in the Building (Scotland) Regulations 2004, and the current edition applies to building warrants submitted on or after 5 June 2023. Northern Ireland has its own building regulations again, so check locally rather than assuming an English Approved Document is the operative document where you live.

For the work itself, GOV.UK's position is that you must check whether you need approval before you construct or change buildings in certain ways, and that approval comes from a building control body, either a local authority building control department or a private registered building control approver. The reason to care is practical as well as legal: without approval you will not have the certificates of compliance you may need when you want to sell your home.

A competent investigation starts outside and underneath, not with a meter held against the plaster. It establishes where the damp-proof course is and whether anything bridges it, what the external ground levels are doing, whether gutters, downpipes, gullies and drains are discharging where they should, and whether the floor construction has a membrane and whether it connects to the wall. Only after that does the question of a waterproofing system arise, and for most houses the answer is repair and levels rather than a system at all.

Where the building really is holding back ground water, the job changes character. Approved Document C points to BS 8102 for walls and floors subject to groundwater pressure, including basement walls, and flags that water pressure is likely in buildings on very permeable strata such as chalk, limestone or gravel. It also sets a trigger for site drainage: where the water table can rise to within 0.25m of the lowest floor of the building, or where surface water could enter or adversely affect the building, either the ground to be covered by the building should be drained by gravity or other effective means of safeguarding the building should be taken.

LokalMatch is how you collect comparable quotations once you know what you are asking for. Describe the property and the damp once, including where it appears, when it appears and what you have already checked outside, add your postcode, and damp and waterproofing contractors covering your area contact you. They pay for the requests they receive. LokalMatch neither carries out the work nor sets the price, and does not vet, rank or recommend any firm, so asking each surveyor what they ruled out, and whether the person diagnosing the problem also sells the cure, is still your job.

An applied system, whether a tanking render, a membrane or an injected course, is a barrier placed between the moisture and the room. It is the right response where moisture genuinely cannot be excluded any other way, most obviously below ground and where the structure holds back water. It is the wrong response where the moisture has an ordinary route in that could simply be closed.

Lowering a path that has been built up above the damp-proof course, cutting back render that carries moisture across it, repairing a cracked gully, re-laying a downpipe into a drain, or providing subsoil drainage on the up-slope side of a building all attack the cause. Approved Document C explicitly contemplates the last of these for suspended floors on sloping sites, and requirement C1 makes adequate sub-soil drainage a requirement in its own right where it is needed to stop ground moisture reaching the interior or damaging the building.

There is also a sequencing point that saves money. If ground levels, drainage or a leaking pipe are contributing, deal with those first and let the wall dry before deciding whether anything further is needed. A wall that has been wet for years does not dry in a fortnight, and a system installed while the cause is still running will be judged on a building that was never given the chance to recover.