What Substrates Can Polyurethane Waterproof Coatings Be Applied To?

Polyurethane waterproof coatings have become a preferred choice for contractors, engineering project managers, and waterproofing material wholesalers because of their strong adhesion, durability, and flexibility across a wide range of substrates. However, one of the most common questions professionals ask is:

“What substrates can polyurethane waterproof coatings be applied to?”

This detailed guide will break down every type of substrate compatible with polyurethane coatings, the surface preparation required, real engineering applications, and important considerations when choosing between oil-based and water-based polyurethane waterproof systems.

Overview: Why Polyurethane Waterproof Coatings Work on Multiple Substrates?

Polyurethane waterproof coatings are known for their:

Strong adhesion to porous and non-porous surfaces
High elasticity (can withstand structural movement)
Seamless film formation
Chemical and abrasion resistance
Compatibility with top coatings, primers, and reinforcing fabrics

Because polyurethane forms a high-bonding, elastic, continuous waterproof layer, it can adhere to:

Rigid substrates（concrete、tiles、stone）
Flexible substrates（metal roofs、PVC sheets）
Absorbent substrates（wood、cement mortar）
Low-absorbent substrates（coated metal、ceramic）

Its versatility makes it ideal for:

Residential waterproofing
Commercial building maintenance
Infrastructure engineering
Industrial roofing and floor protection
Large-scale waterproofing projects

This unmatched versatility is also why polyurethane waterproof coatings are widely used by contractors and selected by bulk material purchasers worldwide.

Concrete Substrates: The Most Common Application Surface

Concrete is the primary substrate for polyurethane waterproofing. Because concrete is porous, breathable, and structurally dynamic, polyurethane’s flexible membrane effectively prevents water penetration and resists:

Micro-cracking
Shrinking and expansion
Hydrostatic pressure

Polyurethane coatings are widely used on:

Common concrete areas
Roof slabs
Basements
Podiums
Tunnels
Water tanks
Balconies
Lift pits
Sewage treatment areas
Concrete floors for industrial buildings

Surface preparation requirements

To achieve maximum performance, concrete surfaces must be:

Clean and free of laitance
Dry or slightly damp (depending on the product)
Structurally sound and free of loose particles
Repaired for cracks or honeycombs
Primed using compatible polyurethane primers

New vs. old concrete

New concrete should be fully cured (≥14 days for water-based, ≥28 days for oil-based).
Old concrete must be thoroughly cleaned, and repairs should be completed before coating.

This step ensures the polyurethane coating forms a uniform, long-lasting waterproof membrane.

Metal Substrates: Steel, Aluminum, and Metal Roofing Sheets

Polyurethane coatings are excellent for metal surfaces because they offer:

Strong adhesion to steel, aluminum, and galvanized sheets
High flexibility to withstand thermal expansion
UV and weather resistance（water-based systems perform better outdoors）
Chemical resistance suitable for industrial environments

Compatible metal substrates

Corrugated steel roofing sheets
Aluminum panels
Metal gutters and flashing
Steel tanks and pipes
Industrial metal roofs
Prefabricated metal buildings

Surface preparation

Metal surfaces require:

Rust removal（ST2–ST3 or sandblasting for severe corrosion）
Oil, grease, and dirt elimination
Proper priming using anti-corrosive or polyurethane primers

Important note:

Because metal undergoes huge temperature changes, the coating must be:

Flexible
UV-resistant（water-based recommended for exposed areas）
Well-bonded

This ensures long-term stability and prevents peeling, blistering, or cracking.

Wooden, Plywood, and Insulation Board Substrates

Wood and insulation substrates are absorbing, flexible, and prone to dimensional changes. Polyurethane’s elasticity and penetrating adhesion make it a suitable waterproofing solution.

Common wooden or lightweight substrates

Plywood floors
Timber roofs
Wood panels
OSB boards
Insulation boards（XPS、EPS、PU boards）

Preparation and application

Because wood expands and contracts, the coating must be reinforced:

Apply primer for better penetration
Use reinforcing fabric at joints
Avoid applying on wet or swollen wood
Ensure structural stability before waterproofing

For insulation boards

XPS and EPS are low-absorbent. Therefore:

A specialized polyurethane primer
Or light sanding

is required to ensure proper bonding.

Polyurethane waterproof coatings in these areas help prevent moisture absorption, warping, mold formation, and material degradation.

Tiles, Stone, Mortar, and Other Hard Finishes

Many contractors waterproof over existing tiles to avoid demolition costs, noise, and dust. This approach is excellent for renovation projects.

Typical application areas

Bathroom tile floors
Balcony tiles
Kitchen tile substrates
Exterior stone surfaces
Mosaic floors

Surface preparation

Because tile and stone surfaces are smooth, bonding must be improved by:

Mechanical grinding
Acid etching (when appropriate)
Applying adhesion-enhancing polyurethane primers

Once treated, polyurethane forms a highly durable membrane capable of handling:

Micro-movement of tile layers
Grout line expansion
Moisture absorption differences

This makes it ideal for bathroom waterproofing and balcony renovation projects.

PVC, EPDM, TPO, and Old Waterproof Membrane Surfaces

These substrates are traditionally challenging because they are:

Non-porous
Flexible
Chemically resistant
Low-adhesion

However, with the right primer and techniques, polyurethane coatings can be successfully applied.

Compatible substrates

PVC roofing membrane
TPO waterproofing sheets
EPDM rubber roofing
Old polyurethane or acrylic coatings
Aging bituminous membranes

Critical application steps

Thorough cleaning
Light sanding for mechanical adhesion
Applying specialized primers
Using flexible polyurethane systems

These steps allow contractors to repair old waterproofing layers without full replacement, cutting costs and reducing project time.

Choosing Between Oil-Based and Water-Based Polyurethane Coatings Based on Substrates

Oil-based polyurethane requires a protective topcoat if used outdoors, whereas water-based polyurethane can be directly exposed.

Oil-based Polyurethane

Pros:

Strong bonding on metal and concrete
High tensile strength
Excellent chemical resistance

Limitations:

Poor UV resistance
Tends to chalk or harden when exposed
Requires protective topcoat for external surfaces

Water-based Polyurethane

Pros:

UV-resistant and suitable for exposed conditions
Environmentally friendly, low odor
Ideal for slightly damp concrete surfaces
Excellent flexibility

Best for:

Rooftops
Exterior walls
Metal roofs exposed to sunlight
Wet areas (bathrooms, kitchens, balconies)

Substrate-based recommendation

Substrate	Recommended Type	Notes
Concrete	Water-based / Oil-based	Exterior = water-based preferred
Metal	Oil-based or 2-component	Outdoor requires topcoat
Tiles	Water-based	Better bonding with primer
Wood	Water-based	More flexible, breathable
PVC/TPO/EPDM	Water-based / Oil-based	Surface must be sanded
Old membranes	Water-based	Less risk of chemical reaction

Why Contractors Choose YURU Waterproof as Their Polyurethane Coating Supplier?

As a leading waterproof materials manufacturer, YURU Waterproof supplies high-performance polyurethane waterproof coatings for global wholesalers, contractors, and engineering firms.

Our advantages

Full product range: oil-based, water-based, and 2-component polyurethane coatings
Compatible with all major substrates listed in this guide
Support bulk purchasing and OEM manufacturing
Professional technical consultation for projects
Export-grade packaging and logistics support
Stable supply for distributors and engineering companies

With years of experience in waterproof coatings, grouting materials, and flooring systems, YURU Waterproof ensures product reliability, technical accuracy, and long-term stability—critical factors for large engineering projects.

FAQs: Polyurethane Waterproof Coating Substrates

1. Can polyurethane waterproof coatings be applied to damp surfaces?

Water-based polyurethane can be applied to slightly damp surfaces, but oil-based systems require dry substrates.

2. Can polyurethane be applied over old tile surfaces?

Yes. After sanding and priming, polyurethane forms a strong waterproof membrane over tiles.

3. Is a primer always required before applying polyurethane coatings?

Not always, but primers significantly improve adhesion on metal, tiles, and non-porous surfaces.

4. Which polyurethane type is best for roofs?

Water-based polyurethane is generally recommended because it is UV-resistant and suitable for external exposure.

5. Can polyurethane waterproofing be used on wooden floors?

Yes. Water-based polyurethane is more suitable because it accommodates expansion and contraction.

6. Can polyurethane be used to repair old waterproof membranes?

Yes, with correct surface preparation and proper primer selection.

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What Substrates Can Polyurethane Waterproof Coatings Be Applied To?

Overview: Why Polyurethane Waterproof Coatings Work on Multiple Substrates?