What is the difference between roof overlay and full roof replacement?

Roof overlay applies a liquid waterproofing membrane directly over the existing roof substrate without removal, reducing programme time, cost and waste. Full replacement involves stripping the existing roof to deck level and installing new build-up. Overlay is suitable when the substrate is structurally sound with manageable moisture levels (≤6% moisture content). Replacement is required when there is significant structural degradation, excessive moisture saturation, or when insulation upgrades are mandated under Approved Document L.

What is spray-applied waterproofing and how does it work?

Spray-applied waterproofing uses cold-spray liquid rubber membranes (such as SprayGrade or BelowGrade) that are sprayed onto prepared substrates using airless or plural-component spray equipment. The liquid cures to form a seamless, elastomeric membrane that bonds to the substrate and bridges cracks and movement joints. Output rates can exceed 600m² per day for large commercial roofs, with cure times ranging from minutes to hours depending on the system.

What substrates can liquid rubber waterproofing be applied to?

Liquid rubber membranes can be applied to concrete, masonry, metal decking, single-ply membranes, bituminous felt, asbestos cement sheets (ACM), wood decking, and existing waterproofing systems. Each substrate requires specific preparation protocols including cleaning, degreasing, repair of defects, and priming where necessary. Silicone-based sealants must be completely removed due to chemical incompatibility. Substrate moisture must be ≤6% for standard applications.

What is the difference between Liquid Rubber and Prokol systems?

Liquid Rubber systems (BelowGrade, HBS200, SprayGrade) are flexible waterproofing membranes designed for water ingress prevention on roofs, below-ground structures and details. Prokol systems (Rocathaan HotSpray, TopSpray35, Monoseal, Profix, FireGuard Pro) are high-performance protective coatings offering UV stability, traffic resistance, chemical resistance, fire protection and rapid cure polyurea technology. Liquid Rubber waterproofs; Prokol protects and enhances durability.

Do I need a survey before specifying a roof refurbishment system?

Yes. A professional roof survey is essential before specification. This should include visual inspection, moisture assessment using calibrated meters (readings ≤6% required), structural assessment of deck condition, identification of detailing requirements (penetrations, parapets, gutters, upstands), and access considerations. Our Inspection Checklist and Moisture Assessment Guide provide the methodology for comprehensive pre-specification surveys.

What fire certifications do Forti Nova systems hold?

Rocathaan HotSpray PA 260-FR pure polyurea is certified to BS EN 13501-5 B_ROOF(t4) by Warrington Fire, meeting Approved Document B requirements for external fire exposure. FireGuard Pro 200 is a reaction-to-fire classified surface coating (A2-s1,d0 cited, EN 13501-1:2007+A1:2009, Report 18831B) — it is not a structural steel fire-protection system. Fire protection specification is system-dependent and requires confirmation against the fire strategy and applicable product assessment.

What below-ground waterproofing standard do you comply with?

BelowGrade system is engineered for BS 8102:2022 Type A (barrier protection) waterproofing of basements, retaining walls and civil infrastructure. The system provides the gas and water barrier properties mandated by the standard for Grade 3 (habitable) and Grade 2 (non-habitable) protected spaces.

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Important: All technical datasheets and safety documentation must be reviewed prior to specification and installation. Any warranty is project-specific and conditional on full compliance with manufacturer application requirements and trained approved applicator installation.

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