The short answer is that damp-proofing guarantees vary significantly between companies and should be read carefully. A guarantee typically covers the specific treatment installed under defined conditions, but it does not cover everything — and understanding the exclusions is just as important as the headline promise.
01
What a typical guarantee covers
Most reputable damp-proofing guarantees cover the chemical DPC treatment itself for a specified period, typically 10 to 30 years. This means the injected barrier should prevent rising moisture from passing through the treated masonry at the injection line. Some guarantees also cover the replastering specification that was applied as part of the treatment. The guarantee applies only to the specific work described in the quotation and completion documentation.
02
What is usually excluded
Common exclusions include: damp from sources other than rising moisture (leaks, condensation, penetrating damp), damage caused by alterations to the property after treatment, failure of finishes applied before the wall has dried sufficiently, areas not included in the original scope, and consequential damage. Bridging of the DPC by later building work, raised ground levels or internal alterations can also void the guarantee.
03
Questions to ask before accepting
Is the guarantee backed by the company, an insurer, or both? What happens if the company ceases trading? Does the guarantee transfer to a new owner if the property is sold? Are there specific maintenance requirements you must follow? What is the process for making a claim? A clear, honest guarantee document answers these questions upfront.
04
When to call a specialist
If you have received a quotation with guarantee terms that seem unclear, or if a previous guarantee has not delivered what was promised, a fresh independent assessment can provide clarity on what your property actually needs and what guarantee terms are appropriate for the work specified.
Complimentary survey
Book Your Complimentary Survey
Over 35 years of independent expertise. Written findings included. No sales pressure. No obligation.
Book your complimentary surveyTechnical review
Dan, Director / Surveyor
Last reviewed: July 2026. Advice is general until the property, access and visible evidence have been assessed.
When to arrange a visit
Book an inspection when the problem is persistent, changing, purchase-related or unclear after basic maintenance checks.