Waterproof Blue Liquid DPM — Seamless Floor & Foundation Waterproofing
Waterproof Blue Liquid DPM — Seamless Floor & Foundation Waterproofing
Forget the plastic sheet. Liquid application. No joints. No weak points.
A professional-grade polymer-modified liquid DPM that replaces traditional polythene DPMs and DPCs. Roller or brush applied — seals kicker blocks, concrete floors, block and beam floors, and foundation walls with a fully bonded, crack-bridging barrier. Radon certified.
Why Traditional Plastic DPMs Fail
Polythene sheet DPM has been the industry standard for decades — but it has fundamental weaknesses that no amount of careful installation can fully overcome.
Tears and Punctures During Installation
Heavy plant, boots, rebar, and aggregate all threaten polythene during the pour. Even hairline tears create moisture pathways that defeat the entire membrane. Once buried under concrete, there is no way to inspect or repair the damage.
Cannot Seal Kicker Block Upstands
The kicker block — the short concrete upstand at the base of every wall — is the most common point of damp ingress in new-build floors. Polythene sheet physically cannot wrap around it properly, leaving an open gap between floor and wall that moisture and ground gases exploit freely.
Joints, Overlaps, and Tape Failures
Every overlap is a potential failure point. Tape adheres to dusty, damp polythene poorly. Over time, tape delaminates — and the joint opens. In radon-resistant construction, even a small gap undermines the entire barrier’s performance.
Cannot Follow Complex Geometry
Service penetrations, columns, steps, and irregular shapes require cuts, patches, and custom fabrication — each one a potential weak point. Liquid application follows any geometry without special detailing or additional materials.
What is Waterproof Blue Liquid DPM?
Waterproof Blue is a premium polymer-modified liquid damp proof membrane designed for professional use on UK construction sites. It is applied by roller or brush directly to concrete, masonry, and blockwork substrates — creating a monolithic, fully bonded waterproof barrier without joints, overlaps, or weak points.
Unlike polythene sheet DPMs, Waterproof Blue bonds chemically to the substrate. It cannot move, bunch, or tear during the pour. As a liquid DPM paint, it flows into every surface irregularity, corner, and penetration — forming a seamless skin that polythene sheet is physically incapable of replicating.
It is certified as a radon barrier membrane, making it the only liquid DPM on the market that can satisfy radon-resistant construction requirements for UK Building Regulations while simultaneously solving the kicker block problem. In high-radon areas across the UK — Devon, Cornwall, Yorkshire, Northamptonshire, Derbyshire, and others — this combination of performance is critical.
The 2-coat system (minimum 800g/m² total) is tiled or screed-ready within 24–48 hours. It is VOC-free, water-based, and suitable for both horizontal and vertical application.
Waterproof Blue is the right choice for block and beam floor DPM, kicker block waterproofing, concrete slabs, foundation walls, and replacing plastic DPC in thin-joint masonry. It is not designed for hydrostatic water pressure — for basements with active water ingress, see Poseidon; for flat roofs, see The GOAT.
At a Glance
- Roller or brush applied — no special tools
- Bonds to substrate — fully adhered, no movement
- Seamless monolithic barrier — no joints
- Seals kicker blocks and complex geometry
- Certified radon barrier (with dedicated certificate)
- Crack-bridging — stays intact as concrete cures
- VOC-free, water-based — safe to use indoors
- Tile-ready in 24–48 hours
- No primer required
- No corner tapes or reinforcement strips needed
- Horizontal and vertical application
- UV resistant
Six Reasons to Specify Waterproof Blue
Every feature is designed to solve a real problem that plastic DPM cannot address.
Radon Barrier Certified
Waterproof Blue carries a dedicated Radon Certificate — meeting UK Building Regulation requirements for radon-resistant construction. Liquid application seals every gap including kicker block upstands, which polythene sheet consistently misses. Download the certificate below.
Seamless — No Joints or Weak Points
The liquid membrane cures to a single continuous film with no overlaps, joints, or tape lines. There are no seams for moisture to track along and no reliance on adhesive bonds that degrade over time. One monolithic barrier from edge to edge.
Seals Kicker Blocks — Plastic Cannot
The kicker block upstand is where plastic DPM always fails. Waterproof Blue flows around and up the face of the upstand, creating a continuous seal at the most vulnerable junction in the entire floor build-up. No tapes, no additional products, no compromise.
Crack-Bridging Flexibility
The cured membrane is flexible and elastic. As new concrete cures and hairline cracks develop during settlement, Waterproof Blue bridges them — maintaining an unbroken seal. Rigid products crack with the substrate and fail. Waterproof Blue moves with it.
VOC-Free, Water-Based
Zero VOC content makes Waterproof Blue safe for indoor use without ventilation precautions. Water-based cleanup. No solvent smell. Suitable for use in occupied or partially enclosed spaces. Compliant with stringent indoor air quality requirements.
2-Coat System — Tile in 24–48h
Apply two coats crosswise (minimum 800g/m² total). The second coat is applied perpendicular to the first to ensure complete coverage. Tiling with cement adhesive class C2 or dispersion adhesive class D2TE (EN12004) can begin after 24–48 hours.
Radon & Underground Gas Barrier
In significant areas of the UK, Building Regulations require new-build ground floors to incorporate a radon-resistant barrier. Waterproof Blue satisfies this requirement — and goes further.
Why UK Radon Protection Matters
Radon is a naturally occurring radioactive gas that enters buildings through the ground. Public Health England identifies elevated radon zones across Devon, Cornwall, the Peak District, Northamptonshire, Yorkshire Dales, the Cotswolds, and parts of Scotland. In Affected Areas, Part C of the Building Regulations requires radon-resistant construction measures for new ground floors.
A polythene sheet DPM provides some radon resistance — but it has one critical flaw: it cannot properly seal the kicker block upstand where the floor membrane meets the wall. This junction is consistently the most significant radon entry route in new-build housing. Waterproof Blue is a radon barrier membrane UK that eliminates this gap.
- Dedicated Radon Certificate (downloadable below)
- Seals kicker block upstands — the critical gap polythene misses
- Continuous monolithic film — no gaps, no tape joints
- First line of defence against all ground gases
- Meets UK Building Regulation requirements
- Suitable for Part C radon-resistant construction
- Applicable to high radon zones across England, Wales & Scotland
- Can be combined with sump systems for enhanced protection
Where to Use Waterproof Blue
Waterproof Blue is a versatile liquid DPM — suitable for most ground-bearing and substructure applications. Below is a full reference guide.
| Location / Substrate | Suitable? | Notes |
|---|---|---|
| Block and beam floors | ✓ Yes | Primary use case. Apply over the blocks, beams, and infill blocks. The liquid bridges all joints. |
| Kicker block upstands | ✓ Yes | The best solution available — liquid application seals the upstand face fully. Polythene sheet cannot do this. |
| Concrete slabs | ✓ Yes | New and existing slabs. Clean, sound surface required. Fills hairline cracks. |
| Foundation walls (internal face) | ✓ Yes | Vertical application. Forms a bonded barrier against rising damp and ground moisture. |
| Basement floors (no hydrostatic pressure) | ✓ Yes | Suitable for low-level damp control only. If water is pooling or there is active ingress under pressure, use Poseidon. |
| External surfaces | ✓ Yes | Foundations and retaining walls. UV resistant. Apply before backfilling. |
| Under screed | ✓ Yes | Apply Waterproof Blue, allow to cure, then lay screed over the sealed surface. |
| Replace plastic DPC (thin-joint masonry) | ✓ Yes | Apply as a liquid DPC to the mortar course — eliminates the need for polythene DPC strips. |
| Wet rooms / bathrooms | ✗ No | Use Poseidon for wet room applications. Poseidon is specifically formulated for tile-over wet area use. |
| Flat roofs | ✗ No | Use The GOAT for exposed flat roof and balcony applications. |
| Hydrostatic / standing water pressure | ✗ No | Not designed to resist positive water pressure. Use The GOAT or a tanking system for areas with active water ingress. |
Application in 3 Steps
Waterproof Blue is designed for ease of application. No primer. No specialist equipment. Roller or brush — done.
Prepare the Surface
Ensure the substrate is clean, sound, and free of standing water. Fill any cracks or joints wider than 5mm with a paintable waterproof sealant. Allow filler to cure before applying Waterproof Blue. Loose material, dust, and contamination should be removed. No priming required.
Apply Two Coats
Apply the first coat by roller or brush at a minimum of 400g/m². Ensure complete coverage — especially around kicker blocks, upstands, and penetrations. Apply the second coat crosswise to the first, again at minimum 400g/m². Total minimum consumption: 800g/m². Check carefully for pinholes or missed areas — these must be over-coated.
Tile or Screed After 24–48h
Allow Waterproof Blue to cure fully — typically 24–48 hours depending on temperature and humidity. Tile using a cement adhesive class C2 or a dispersion adhesive class D2TE per EN12004. Alternatively, lay screed directly over the cured membrane. Do not apply adhesive or screed to membrane that is still wet or tacky.
Download the full install guide: Waterproof Blue Installation Guide (PDF)
Technical Specification
Full technical data is available in the product data sheet. Key specification data is summarised below.
| Coverage | Minimum 800g/m² total (2 coats × minimum 400g/m² per coat). 10kg covers approximately 12–12.5m². |
| Number of Coats | 2 — apply second coat crosswise on first coat |
| Application Method | Roller or brush. No specialist equipment required. |
| Cure Time (before tiling) | 24–48 hours (dependent on temperature and humidity) |
| Tiling Adhesive Class | Cement adhesive class C2 or dispersion adhesive class D2TE per EN12004 |
| VOC Content | Zero (VOC-free) |
| Base | Polymer-modified, water-based |
| Colour | Blue |
| Flexibility | Flexible and elastic when cured — crack-bridging |
| UV Resistance | UV resistant |
| Orientation | Horizontal and vertical (floors and walls) |
| Primer Required | No |
| Certifications | Radon Barrier Certificate |
| Standards | Tiling adhesive compatibility per EN12004 |
| Available Pack Sizes | 10kg (roller) — £79.99 | 5kg (brush) |
Waterproof Blue vs Other DPM Solutions
See how Waterproof Blue stacks up against the most common alternatives specified on UK construction projects.
| Property | Waterproof Blue Liquid DPM |
Polythene Sheet DPM |
Sand Cement Screed |
Tanking Slurry |
|---|---|---|---|---|
| Radon barrier certified | ✓ Yes | Partial — misses kicker block | ✗ No | ✗ No |
| Seals kicker block upstand | ✓ Yes | ✗ No | ✗ No | Partial |
| Seamless — no joints | ✓ Yes | ✗ No — overlaps required | ✓ Yes | ✓ Yes |
| Bonded to substrate | ✓ Yes | ✗ No — unbonded | Partial | ✓ Yes |
| Crack-bridging | ✓ Yes | Yes — if undamaged | ✗ No — rigid | ✗ No — rigid |
| Resistant to puncture during pour | ✓ Yes | ✗ No — easily torn | ✓ Yes | ✓ Yes |
| Corner tapes / reinforcement needed | ✓ None required | ✗ Tape essential | N/A | Sometimes |
| Tile directly over membrane | ✓ Yes — 24–48h | Not directly | ✓ Yes | ✓ Yes |
| VOC-free | ✓ Yes | ✓ Yes | ✓ Yes | Varies |
| Complexity of installation | Low — roller or brush | Medium — laps and taping | Medium — screeding trade | Medium — two coats + drying |
Technical Documents
Download the full product data sheet, installation guide, safety data sheet, and radon certificate below.
Frequently Asked Questions
The most common questions about Waterproof Blue Liquid DPM — answered.
A liquid damp proof membrane (liquid DPM) is a polymer-modified coating applied by roller or brush directly to concrete or masonry substrates. When cured, it forms a continuous, flexible waterproof film that prevents ground moisture from rising through the floor build-up.
Unlike traditional polythene sheet DPM — which is laid loose and relies on taped overlaps — a liquid DPM bonds chemically to the substrate. This creates a monolithic barrier without joints, overlaps, or seam lines. Waterproof Blue is a liquid DPM UK product formulated for professional and self-build construction.
Yes. Waterproof Blue is specifically designed as a direct replacement for traditional polythene sheet DPMs. It provides equal or superior moisture resistance while eliminating all the failure modes associated with plastic sheet — tears during the pour, joint failures, and the inability to seal kicker block upstands.
For new-build ground floors — including block and beam, ground-bearing slabs, and foundation walls — Waterproof Blue can be used in place of polythene DPM. Where radon protection is also required, Waterproof Blue has a distinct advantage: it provides a fully sealed, certified radon barrier including at the kicker block junction.
Yes. Waterproof Blue carries a dedicated Radon Certificate and functions as a certified radon barrier membrane UK. It meets the requirements for radon-resistant construction under UK Building Regulations (Part C).
Critically, because it is a liquid, Waterproof Blue seals every part of the floor build-up — including the kicker block upstand, which is the most common radon entry route that polythene sheet DPM misses. For properties in UK Affected Areas (Devon, Cornwall, Yorkshire, Northamptonshire, Derbyshire, and more), this makes Waterproof Blue a significantly more reliable solution than polythene sheet alone.
Download the Radon Certificate from the documents section above.
The minimum application rate is 800g/m² total across two coats (approximately 400g/m² per coat). A 10kg unit covers approximately 12–12.5m².
To calculate your requirement: measure the total floor area in m², divide by 12.5 to get the number of 10kg units required, and add an allowance for wastage and vertical surfaces (kicker blocks, upstands). For larger projects, contact us for bulk pricing.
Do not under-apply. If coverage is below 800g/m² the membrane may not achieve full waterproofing performance. Check for complete blue coverage after each coat before proceeding.
Yes. Once fully cured (24–48 hours), tiles can be laid directly over Waterproof Blue using a cement adhesive class C2 or a dispersion adhesive class D2TE per EN12004.
Do not use standard S1 cement adhesives that are not rated C2 — ensure your tile adhesive meets the required performance class for use over flexible membranes. Do not tile until the membrane is fully cured and no longer tacky to the touch.
Yes — and this is one of Waterproof Blue’s most important advantages over polythene sheet DPM. The kicker block upstand (the short concrete upstand at the base of every external wall) is where floor DPM meets wall DPC. Polythene sheet physically cannot make a reliable sealed joint at this junction.
Waterproof Blue is applied by roller or brush and flows up and around the kicker block face, creating a continuous sealed junction between floor and wall. No corner tapes, no reinforcement strips, no specialist contractor — just one product applied seamlessly across the entire floor and up the upstand face.
No. Waterproof Blue is not designed to resist hydrostatic water pressure or active water ingress. It is suitable for damp control — preventing moisture vapour and low-level ground moisture from migrating through floors and walls — but not for situations where water is present under positive pressure.
For basements with active water ingress, seeping walls, or any situation involving standing water, use Poseidon — which is formulated specifically for positive water pressure scenarios. For flat roofs and exposed waterproofing, use The GOAT.
Waterproof Blue is a ground-floor and substructure DPM. It is designed for application to concrete floors, block and beam floors, kicker blocks, and foundation walls — where the challenge is moisture vapour rising from the ground. It is also a certified radon barrier. It is not suitable for areas with standing water or hydrostatic pressure.
Poseidon is a wet room and high-moisture waterproof membrane. It is designed for application in bathrooms, wet rooms, and areas subject to regular water contact. It is formulated for use under tile adhesive in splash and wet-zone environments and for resisting hydrostatic pressure from direct water application.
In short: use Waterproof Blue below the floor and at the foundation. Use Poseidon in wet rooms, bathrooms, and areas with active or pressurised water. If you are unsure, contact us and we will specify the right product for your project.
Ready to Specify Waterproof Blue?
The professional liquid DPM that solves the problems polythene sheet cannot. Radon certified, seamless, and tile-ready in 24–48 hours. Free UK delivery available.