Damp Proofing & Waterproofing
in Hertfordshire
Rising damp, penetrating damp, basement waterproofing — diagnosed correctly, treated permanently. Free survey, written specification, 10-year guarantee.
Damp in Hertfordshire: What You're Actually Dealing With
Damp is one of the most misdiagnosed problems in UK housing. The term covers three completely different conditions — rising damp, penetrating damp, and condensation — each with a different cause, a different treatment, and a very different cost. Treating the wrong type wastes money and leaves the actual problem untouched.
Hertfordshire's housing stock makes this more complicated, not less. The county's dominant property type — the 1930s semi-detached house — has a physical DPC that is now 90 years old. In many cases, external render, paving, or soil has been raised above the DPC line over the decades, bridging it and allowing moisture to bypass it. The result looks exactly like rising damp but is actually a bridged DPC — and the fix is lowering the external ground level, not injecting a new chemical DPC.
TCM's damp surveys start with a diagnosis, not a treatment recommendation. We use a calibrated moisture meter, thermal imaging, and a thorough external inspection before specifying any treatment. The written survey report tells you what type of damp you have, what caused it, and what the correct treatment is — before any work is agreed.
Where damp has caused structural damage — spalled masonry, failed lintels, or compromised wall ties — the structural repair is specified alongside the damp treatment. Treating damp in isolation without addressing the structural consequence is a common cause of repeat problems. The structural repairs service covers the full range of masonry and structural interventions that follow a damp diagnosis.
Free Damp Survey
TCM's free survey covers moisture meter readings, thermal imaging, external inspection, and a written diagnosis report. No charge, no obligation.
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Damp Proofing & Waterproofing Services
Click each treatment type to see the full description, methods, and cost guidance.
The Most Common Damp Misdiagnoses
Treating the wrong type of damp is the single biggest cause of wasted money in damp remediation. These are the patterns TCM encounters most often in Hertfordshire.
| Symptom | Actual Cause |
|---|---|
| Tide mark at low level, peeling paint at skirting | Often a bridged DPC — external render, paving, or soil raised above the DPC level. Lowering the external ground level resolves it without any chemical treatment. |
| Damp patches on external walls after rain | Failed pointing, cracked render, or blocked gutters. The moisture source is external and above ground — not rising. |
| Black mould on cold walls and corners, especially in winter | Condensation — warm moist air hitting cold surfaces. Common in poorly ventilated bathrooms, kitchens, and bedrooms with inadequate heating. |
| Damp in basement after heavy rain | Hydrostatic pressure from a high water table or surface water drainage failure. Rising damp does not cause flooding — this is groundwater ingress. |
The structural repair signs guide covers when damp symptoms indicate a deeper structural problem that requires more than a damp treatment.
Damp Proofing Costs in Hertfordshire (2025–26)
Prices below reflect TCM's current market rates for Hertfordshire and North London. All quotes are fixed-price — no hidden extras. The final cost depends on the area affected, the treatment specified, and the extent of replastering required.
| Treatment | Typical Cost |
|---|---|
| Chemical DPC injection only | £70–£120 per linear metre |
| Chemical DPC + salt-resistant replastering | £150–£250 per linear metre |
| Penetrating damp — repointing (per m²) | £25–£50 per m² |
| Penetrating damp — render repair/application | £35–£65 per m² |
| Basement waterproofing — Type C CDM | £80–£150 per m² |
| Basement waterproofing — Type A tanking | £40–£80 per m² |
| Combined Type A + C (habitable basement) | £120–£200 per m² |
| Full rising damp treatment (3-bed semi) | £2,500–£5,000 |
How TCM's Damp Proofing Process Works
Free Damp Survey
TCM's surveyor visits the property, uses a calibrated moisture meter and thermal imaging, inspects the external fabric, and produces a written diagnosis report. No charge, no obligation.
Written Specification & Fixed-Price Quote
The report is followed by a written specification of the treatment and a fixed-price quote. No vague estimates — the price includes all materials, labour, and making good.
Treatment Preparation
Furniture and floor coverings are protected. Affected plaster is hacked off to expose the masonry where required. Drainage and ventilation are checked before treatment begins.
DPC or Waterproofing Installation
Chemical DPC injection, tanking, CDM installation, or external repairs are carried out to the written specification. Building control notification is made where required.
Salt-Resistant Replastering
Where rising damp treatment has been carried out, the walls are replastered with a salt-resistant backing coat and finish coat. Drying time is confirmed before decoration.
Completion & 10-Year Guarantee
The completed work is inspected and signed off. A written 10-year workmanship guarantee is issued. Drying times and decoration advice are provided in writing.
From Our Work
What TCM Actually Finds on Damp Surveys in Hertfordshire
The most common damp pattern TCM encounters in Hertfordshire is not rising damp — it's a bridged DPC. In the 1930s semis that dominate Borehamwood, Radlett, Bushey, and Watford, the original physical DPC sits at roughly 150mm above external ground level. Over 90 years, external render has been applied over the brickwork, soil has built up in flower beds, and paving has been relaid at a higher level. The DPC is still there and still working, but moisture is bypassing it by travelling through the render or soil that bridges it.
The presenting symptom is identical to rising damp: a tide mark at low level, peeling paint at skirting height, and elevated moisture readings at floor level. A moisture meter reading alone cannot distinguish between the two. The difference is visible only on external inspection — and the fix is lowering the external ground level or cutting back the render below DPC level, not injecting a new chemical DPC.
The second most common pattern is penetrating damp misidentified as rising damp. In Borehamwood and Radlett, we regularly survey properties where the damp patches on internal walls correlate precisely with failed pointing on the external elevation — particularly on north-facing walls where mortar deteriorates faster. The moisture meter readings are elevated, the homeowner has been told they need a DPC, but the source is horizontal, not vertical.
The third pattern is condensation in properties that have had cavity wall insulation installed. Cavity wall insulation reduces the wall's thermal mass and can create cold bridges at the wall ties, producing condensation on internal surfaces that looks like penetrating damp. Thermal imaging identifies this immediately; a moisture meter alone does not.
In every case, the diagnosis determines the treatment. TCM does not specify a treatment before completing the survey — and the survey report is provided to the homeowner regardless of whether they proceed with us.
Damp Proofing Questions Answered
Related Services
Structural Repairs
Underpinning, crack stitching, RSJ installation
Property Refurbishments
Full property renovation including damp treatment
Basement Conversions
Basement waterproofing as part of a conversion
Roofing Services
Flashing and gutter repairs that cause penetrating damp
Plastering & Decorating
Salt-resistant replastering after damp treatment
Start With a Free Damp Survey
TCM's free survey covers moisture meter readings, thermal imaging, external inspection, and a written diagnosis report — before any treatment is agreed. Covering Hertfordshire and North London.
Or view the full property refurbishment service — damp proofing is frequently the first stage of a full renovation.