Compliant Balcony Drainage Reports Supplied with Every Specified Drainage System

Our project-specific drainage reports will give you everything you need to achieve NHBC approval — first time, every time.

80+

Reports Completed

100%

NHBC Approval Rate

Free

No Cost To You

BS 8579

Fully Compliant

WHY IT MATTERS

NHBC Now Requires a Compliant Drainage System on Every Balcony

Since NHBC Standards 2021, a piped or controlled drainage system is mandatory on all balcony and terrace areas. Free-draining balconies — where water simply drips to the level below — are no longer acceptable for new-build developments seeking an NHBC Buildmark warranty.

“A drainage system of outlets and downpipes should be provided to all flat roof, balcony and terrace areas.” — NHBC Standards 2024, Section 7.1

With around 80% of all new homes in the UK receiving an NHBC warranty, and NHBC Building Control Services inspecting approximately 50% of new-build properties directly, getting your drainage specification right is not optional — it is a fundamental requirement for project sign-off. Navigating the annual updates to NHBC Standards, alongside BS 8579:2020 and BS EN 12056-3:2000, can be complex and time-consuming. That is why AliDeck’s Technical Team produces a bespoke, project-specific Drainage Specification Report — giving you a compliant, fully evidenced drainage strategy ready to submit to NHBC.

CLIENT BENEFITS

Why Developers & Fabricators Choose AliDeck Reports

Beyond our 100% NHBC approval rate, the drainage report service delivers a range of tangible advantages throughout your project lifecycle.

De-Risks Your Project

By following our process, it eliminates the risk of non-compliant specifications reaching site, as your design team can follow our guidance from the outset — preventing costly redesigns, procurement delays, and NHBC rejection..

Accelerates NHBC Sign-Off

The report is a ready-made submission document that addresses all of NHBC’s drainage requirements in one place, reducing back-and-forth with inspectors and keeping your programme on track.

Protects Your NHBC Warranty

The report provides documented evidence that your drainage strategy has been professionally designed and calculated, protecting the 10-year Buildmark warranty on your entire development.

Cost Certainty & Right Spec

AliDeck’s “Right Spec Guarantee” ensures the report proposes the most cost-effective compliant solution — preventing over-engineering, unnecessary expenditure, and wasted materials.

Simplifies the Fabricator’s Scope

Clear, project-specific technical drawings covering downpipe locations, overflow positions, gutter sizing, and fall requirements remove ambiguity from fabrication and reduce the risk of site clashes.

Prevents Long-Term Defects

A system sized to the 1:50 and 1:100 year storm criteria for your project’s location prevents water ingress, staining, and structural damage — protecting your reputation and reducing warranty claims.

Demonstrates Due Diligence

In the post-Grenfell regulatory environment, with the Building Safety Act now in force, a professionally produced report provides an auditable record of due diligence for NHBC, building control, and future transactions.

Completely Free of Charge

The report is provided as part of AliDeck’s technical support service. You receive the benefit of over 80 completed reports’ worth of expertise, applied to your specific project, at no additional cost.

DRAINAGE SYSTEMS

Three Compliant Drainage Options for Every Project

Your report will specify the most appropriate drainage strategy for your balcony type, dimensions, and structural arrangement — from one of three NHBC and BS 8579:2020 compliant approaches.

Deck-Level Piped Drainage

Water is collected at deck level via integrated gutters within the AliDrain system and directed to a downpipe. No fall required on 20mm boards up to 4.25m, or 30mm boards up to 6m. Ideal for most residential balcony configurations.

Soffit Piped Drainage

Drainage infrastructure is concealed within the soffit, providing a clean, unobtrusive appearance without compromising performance. Ideal for projects where aesthetics are as important as technical compliance.

Edge Drainage

Water is directed via a formed soffit drainage tray to a continuous perimeter edge, suitable for balconies projecting up to 2.5m from the building face. Particularly effective for stacked balconies, preventing cascading water onto lower levels.

HOW IT WORKS

Four Simple Steps to Drainage Project Success

From initial enquiry to NHBC-ready report to project success — our streamlined process is designed to make compliance straightforward.

Step 1: Project Review

Contact us, for a Teams or phone call to review your project and discuss the drainage requirements for your balconies and terraces:

  • Number & types of balconies
  • Preferred drainage strategy
  • Downpipe & overflow locations
  • Project programme & timeline

Step 2: Send Drawings

To produce your report, we’ll need the following information:

  • Floor plans, elevations & sections
  • Project location
  • Balcony types, quantities & dimensions
  • Drainage strategy preference
  • Downpipe & overflow positions

Step 3: We Create the Report

Our Technical Team produces a comprehensive, project-specific Drainage Specification Report, including:

  • Hydraulic calculations
  • Product specifications
  • Installation methodology
  • Discharge strategy
  • Compliance references

Step 4: Report Delivered

We send the completed report directly to you. You pass it on to your NHBC inspector as part of your warranty submission.

  • Job done.

100% of clients using our drainage products and reports have achieved NHBC approval.

EXAMPLE REPORT

What Your Drainage Specification Report Looks Like

Each report is produced specifically for your project — not a generic template. It is a professional, structured document that provides the NHBC with all the technical evidence required to approve your balcony drainage strategy.

The example shown here is representative of the reports we produce. All client data is redacted to protect confidentiality, but the format and content are consistent across all projects.

Every Drainage Report Includes:

  • Project-specific hydraulic drainage calculations
  • Balcony type schedules with dimensions and quantities
  • Drainage strategy drawings (plan and section)
  • Product specifications and material standards
  • Installation methodology and fall requirements
  • Downpipe and overflow sizing and locations
  • References to NHBC Standards 2024 and BS 8579:2020
  • Discharge strategy and connection details