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Cellar Waterproofing and a Decayed Lintel on Hempstead Lane, Berkhamsted HP4
A property on Hempstead Lane in Berkhamsted had a cellar with tanking that was not doing its job, a badly decayed timber lintel, and damp in an outbuilding and a bedroom.
Project at a Glance
The Brief
The owners wanted the cellar made usable and the other damp areas dealt with.
The Survey
The surveyor found the existing cementitious tanking did not meet BS 8102 for Type A protection, so a continuous Type C system was needed. The timber lintel had advanced fungal decay, reading 40 percent WME, and needed replacing with a concrete lintel. Outside, the periscopic air brick housings were unsealed.
In the outbuilding, poor air changes had let moisture build up in the bathroom partition, and humidistat fans and a PIV unit were recommended.
The Solution
A full cellar and ventilation package:
- Install a continuous Type C cavity drain system with a sump pump.
- Replace the decayed timber lintel with concrete.
- Seal the periscopic air brick housings.
- Fit humidistat fans and a PIV unit in the outbuilding.
The Work
Works including the cellar system, damp proofing, electrics and plastering were carried out in September 2026.
The Result
The cellar now has a managed drainage system instead of tanking that was letting it down. See our basement waterproofing page, or our page on damp proofing in Berkhamsted.
Frequently Asked Questions
Why does cellar tanking fail?
Cement based tanking can crack or debond, and on its own may not meet BS 8102 for the water pressure involved.
What is BS 8102?
The British Standard for protecting below ground structures against water, covering Type A, B and C systems.
Why replace a timber lintel in a cellar?
Damp cellars cause timber decay. A decayed lintel can lose strength, so it is replaced with concrete.
Damp cellar?
Our CSSW and CSRT trained surveyors find the real cause before recommending any work. Non-invasive survey with a clear written report. No obligation.
Survey carried out by Michael Young at Advanced Damp. Project completed in Berkhamsted, HP4.
Sam Fitzgerald is the founder of Advanced Damp and a working damp and structural waterproofing surveyor diagnosing and treating moisture problems in residential and commercial properties across London and the South East. He is FODCS certified (a Federation of Damp Certified Surveyor) and a member of the Federation of Damp. His hands-on work covers rising damp, penetrating damp, condensation, basement waterproofing to BS 8102, and thermal imaging surveys, and he has personally completed over 400 damp surveys across properties of every type and age. Everything he writes draws directly from jobs he has carried out. He does not write about treatments, products or causes he has not dealt with first-hand in the field.
