Many below-ground construction projects require either waterproofing, gas protection—or both. However, understanding when each is needed, and how their costs compare, can make a significant impact on your budget, construction sequencing, and compliance strategy.
In this guide, we explain the key differences between waterproofing and gas protection systems, compare their typical costs, and highlight how integrated solutions can reduce labour, simplify detailing, and minimise long-term risk.
While they may appear similar in application, gas protection and waterproofing systems serve distinct purposes:
A site investigation report (SIR) will determine whether waterproofing, gas protection, or VOC protection is needed. Not all sites require both—but when they do, selecting the right system combination is critical to avoid sequencing issues, duplicated layers, or compliance failures.
System Type |
Protection Level |
Typical Supply & Install Cost (per m²) |
Example Products |
Damp Proof Membrane |
Damp proofing only |
£10 |
|
Damp proofing & Gas |
£13 |
Hydroprufe 9000 |
|
Damp proofing, Gas & VOC protection |
£14 |
Hydroprufe 6000 |
|
Pre-applied Membrane |
Waterproofing only |
£32 |
|
Waterproofing & Gas |
£36 |
||
Waterproofing, Gas & VOC |
£37 |
||
Self-adhesive Membrane |
Waterproofing only |
£42 |
|
Waterproofing & Gas |
£45 |
||
Liquid-applied Membrane |
Waterproofing only |
£48 |
|
Waterproofing, Gas & VOC |
£50 |
Prices include taped joints where required but exclude protection board.
While the labour approach for taped and welded joints differs, the overall cost and efficiency often balance out. Taped joints are typically faster and simpler to install, making them ideal for standard DPMs and pre-applied membranes. Welded joints, while requiring more specialist labour and equipment, provide a continuous seal that is often preferred on sites with VOCs or hydrocarbon contamination.
For larger areas, welded systems may even prove more economical due to the absence of tapes and reduced overlap detailing. Ultimately, the choice depends on site conditions, warranty requirements, and membrane type.
Taped Joints
Welded Joints
Contaminated Land & VOCs
Sites affected by hydrocarbons, methane, radon, or VOCs often require VOC-rated membranes and sealed joints—raising both material and installation costs. In severe cases, additional ground investigation or laboratory testing may be needed.
In some scenarios, land remediation (e.g., removing or treating contaminated soils) may be more cost-effective than installing high-spec barrier systems. It’s worth weighing the cost of remediation vs. designing around the risk, particularly when VOC protection and third-party verification are involved.
Deeper excavations or high water table zones introduce more hydrostatic pressure, typically necessitating Type C cavity drainage systems with channels, membranes, and sump pumps. These systems:
If self-installation is preferred, this may limit your system options and should be considered during early-stage budgeting and design.
When gas protection systems are required, CIRIA C735 mandates independent verification by qualified inspectors to ensure installation integrity. The frequency of visits will be determined by a number of factors as outlined in CIRA C735 – Complexity of Design, Number of Plots / Buildings, Competency of Installation Work Force and Gas Risk Regime.
Here is an approximate guide:
These costs are often missed in early budgets but are crucial for warranty approval and regulatory compliance—particularly when VOCs or hydrocarbons are involved.
Detailing around pile caps, kicker joints, service penetrations and transitions often drives up cost and complexity. If not planned early, poor detailing can lead to:
When membranes are installed beneath the slab, pile head detailing becomes a major cost centre. Wrapping each pile cap with membrane or liquid coating can be time-consuming and labour-intensive.
While installing membranes above the slab is sometimes done at ground floor level, it is not recommended in VOC or hydrocarbon environments. These contaminants can migrate through cracks or voids in concrete, rendering the barrier ineffective.
Premcrete offers a suite of products designed to streamline detailing, reduce labour, and maintain compliance:
Installing separate waterproofing and gas membranes can double labour time, increase material waste, and raise the risk of detailing errors. Premcrete’ s COMBI-SEAL and COMBI-SEAL PLUS systems offer a streamlined, pre-applied dual membrane that provides:
The best way to manage cost is to align your protection strategy with your site’s actual risks—early.
Premcrete supports main contractors and design teams with:
By working with Premcrete early, you’ll avoid duplication, reduce installation risk, and ensure compliance across both waterproofing and gas protection disciplines.
Let Premcrete help you review your site investigation report and recommend a compliant, cost-effective solution—complete with budget guidance and system options.