1.5mm Aluminium Inspection Chambers - 450mm x 450mm | Deck Version

The deck version of the aluminium inspection chamber sits flush with the roof deck surface, surrounding a deck-level drainage outlet and providing maintenance access through the substrate or surface finish layer above. On a green roof, the chamber is installed over a roof drain before the growing medium, drainage layer or pebble ballast is laid, with the chamber depth and cover height set so that the cover sits at or flush with the finished substrate surface. At 450mm x 450mm, it gives a wider access opening than the 300mm x 300mm deck version, suited to deeper substrate build-ups, more complex drainage outlet details, or any position where the larger working space is specified.

Manufactured in 1.5mm aluminium, powder coated in any RAL colour, and available in four depth options from 150mm to 350mm. The depth must match the installed depth from the deck surface to the drainage outlet below, so the chamber sides contain the substrate layer and the cover sits level with the finished surface. Fabricated to order at the Online Metal Store Ltd facility in Chelmsford, Essex.

Deck Version or Parapet Version: Which Do You Need?

These two versions are installed in completely different positions. Ordering the wrong one for your drainage configuration means a replacement on a made-to-order non-returnable product.

Deck Version (This Product)

The deck chamber is installed vertically into the roof deck over a drainage outlet, drain body or sump that exits through the waterproofing membrane. It is installed before the substrate, growing medium or surface finish is laid around it. The sides of the chamber are surrounded by the substrate layer on all four sides. The cover sits flush with the finished substrate surface to provide tool-free access for cleaning and inspection of the drain below without disturbing the green roof surface layer.

Parapet Version

The parapet chamber is installed into the face of the parapet wall, at a position where the drainage outlet, overflow pipe or weep hole exits through the wall construction. Access is from the outside face of the parapet, not from the roof deck. For the parapet version in the 450mm size, see the 450mm x 450mm parapet inspection chamber.

300x300mm or 450x450mm: Choosing the Right Plan Size

Use the 300mm x 300mm Version When

The drainage outlet is a standard roof drain in a straightforward position, the substrate depth is moderate, and there is no specific reason to require the larger access opening. The 300mm x 300mm deck inspection chamber is the more common specification on domestic green roof extensions and smaller commercial flat roofs.

Use the 450mm x 450mm Version (This Product) When

The drainage outlet or sump is larger than standard, the substrate layer is deep and requires more working space to access the drain below, the drainage outlet has multiple connections or fittings that need to be reached during maintenance, or the project specification calls for the larger chamber for inspection purposes. The extra 150mm in each direction gives meaningfully more access space over a deep substrate layer.

Selecting the Correct Depth

The four options in the size dropdown (150mm, 200mm, 250mm, 350mm) are the depth of the chamber measured from the roof deck surface down to the drainage outlet. Select the depth that matches the vertical distance between the top of the roof deck and the drainage outlet connection point below.

• 150mm: shallow drainage outlet or sump close to the deck surface. Suited to thin build-up flat roof systems.

• 200mm: standard depth for most domestic and light commercial flat roof drainage configurations.

• 250mm: deeper drain outlet or sump position. Suited to warm roof builds with a deeper insulation layer between the deck and drain body.

• 350mm: maximum standard depth for drainage outlets set deep below the deck surface in commercial flat roof and intensive green roof constructions.

Note on cover height: the top of the chamber walls and cover must sit at the finished substrate surface level on a green roof installation. If the growing medium or substrate is 100mm deep and the drain is 200mm below the deck, select the 200mm chamber and set the top of the chamber walls at the finished substrate surface level by packing the chamber base as required. Check the finished surface level and the drainage outlet depth before ordering.

Key Benefits

• Larger 450mm access opening: gives more working space than the 300mm version for accessing drains under deep substrate layers, complex outlet fittings, and intensive green roof build-ups.

• Deck-level flush installation: sits flush with the finished substrate or surface layer, giving unobtrusive maintenance access without protruding above the green roof surface.

• Installed before substrate: placed over the drain on the deck before the growing medium or drainage layer is laid, ensuring the chamber sides are correctly contained within the build-up.

• Four depth options: 150mm, 200mm, 250mm and 350mm to match the vertical distance from deck surface to drainage outlet.

• 1.5mm aluminium, no rust or degradation: suitable for permanent embedding in moist soil and organic growing media without corrosion or dimensional change over the service life of the roof.

• Lift-off cover for tool-free access: the cover removes without tools for quick inspection and cleaning visits.

• Any RAL colour: powder coated to match retention trims, coping or other external aluminium components.

Technical Specifications

• Material: 1.5mm grade aluminium
• Plan Dimensions: 450mm x 450mm (deck opening)
• Depth Options: 150mm, 200mm, 250mm, 350mm (measured from deck surface to drainage outlet)
• Version: Deck -- for installation into the roof deck over a deck-level drainage outlet
• Cover: Flush lift-off aluminium cover for tool-free maintenance access
• Installation Timing: Install before substrate or growing medium layer is laid
• Finish: Polyester powder coating, external grade, any RAL colour
• Applications: Green roof drain access, living roof substrate drainage, flat roof sump inspection, balcony and terrace drainage access
• Price: £75.00 ex VAT (£90.00 inc VAT)
• Fabrication: Made to order, Chelmsford Essex -- non-returnable unless faulty

Installation: Sequencing Matters on a Green Roof

On a green roof, the deck inspection chamber must be installed at the correct stage of the build-up sequence. Getting the sequence wrong means the chamber is either inaccessible under the substrate or incorrectly positioned relative to the finished surface level.

The correct sequence:

• Complete the waterproofing membrane layer across the full deck surface. Ensure the membrane is dressed into the drain body.

• Set the deck inspection chamber over the drain outlet, positioning the chamber sides on the completed membrane surface. The base of the chamber surrounds the drain body.

• Set the finished top of the chamber walls at the level of the intended finished substrate surface. Pack or adjust the chamber base as required to achieve the correct top height.

• Fix the chamber in position. The chamber sides will be surrounded by the drainage layer, substrate or growing medium as the build-up is completed.

• Lay the drainage layer, filter membrane, growing medium and any surface layer around the chamber on all four sides. The substrate surrounds the chamber walls, and the cover sits flush with the finished surface.

• The lift-off cover can be removed at any time for drain inspection and cleaning without disturbing the substrate layer.

For the complete green roof edge detail alongside the deck chamber, use aluminium retention trims at the perimeter and the aluminium drip trim at the exposed outer edge.

Where the 450mm Deck Chamber Is Used

Green and Living Roof Drainage Inspection

The primary application. On green roofs where drainage outlets are set into the deck, the inspection chamber provides maintenance access through the substrate and growing medium layers without having to remove surface material. The 450mm size is used where the drain is larger than standard, where the green roof system is an intensive planted roof with a deeper substrate layer, or where the project specification calls for the larger chamber for inspection and maintenance access purposes.

Extensive Green Roof Systems

Extensive green roofs with sedum or low-growing vegetation typically have substrate layers of 75mm to 150mm. The 450mm deck chamber is used over roof drains within the substrate layer, providing access for the periodic clearance of organic material and debris that accumulates at the drain over the service life of the green roof. Paired with 1.5mm aluminium retention trim at the perimeter, the chamber and trim together complete the drainage maintenance specification for a well-detailed extensive green roof.

Intensive Green Roofs and Planted Terraces

Intensive green roofs with planted areas, trees, or deeper growing media require reliable, accessible drainage inspection points. The 450mm x 450mm size gives the access space needed for drains under deeper build-ups where the 300mm version might be tight for a maintenance operative to work in. The 250mm or 350mm depth options accommodate drainage outlets positioned deeper in the roof build-up for intensive roof constructions.

Roof Terraces and Amenity Decks

On accessible roof terraces and amenity roof decks with a surface finish of pavers, decking boards or bonded aggregate over a waterproofing layer, the deck inspection chamber provides access to drainage outlets beneath the finish layer. On these surfaces, the chamber cover sits flush with the deck finish, giving a neat unobtrusive access point. Order alongside aluminium coping for the parapet and the aluminium drip trim at the roof edge for a complete aluminium-detailed deck specification.

Why Aluminium for a Deck Inspection Chamber

A deck inspection chamber is embedded in moist substrate for the entire service life of the green roof, which may be 25 years or more. Plastic chambers degrade in this environment: they become brittle under UV where the cover is exposed at the surface, and under sustained moisture contact in the substrate. An aluminium chamber does not corrode, does not become brittle at low temperatures, and maintains its dimensional stability over the full service life of the roof.

The 1.5mm gauge provides the structural rigidity needed to resist the lateral pressure of the substrate layer on all four sides of the chamber without deforming, which is particularly important on intensive green roofs with a deep, heavy growing medium layer. A chamber that deflects inward under substrate pressure will not seat the lift-off cover correctly over time.

Why Choose Online Metal Store Ltd

We manufacture all four inspection chamber variants at our Chelmsford facility. For complete green roof specifications combining deck chambers, parapet chambers, retention trims and drip trims, all in the same RAL, contact our team at sales@onlinemetalstore.co.uk or call +44 7907 239290, Monday to Saturday 6:30am to 4:30pm. We can confirm the correct depth for your drainage configuration, advise on chamber count for your drain layout, and quote for the full green roof accessory package.

Related Products

• Aluminium Inspection Chamber 300mm x 300mm | Deck Version -- smaller deck chamber for standard green roof drain details

• Aluminium Inspection Chamber 300mm x 300mm | Parapet Version -- parapet-mounted chamber for wall-base drainage outlets

• Aluminium Inspection Chamber 450mm x 450mm | Parapet Version -- larger parapet chamber for complex parapet outlet details

• 2mm Aluminium Retention Trim – 2.4m Length -- green roof edge retention trim for substrate and ballast

• 1.5mm Aluminium Retention Trim – 2.4m Length -- lighter gauge retention trim for shallow green roofs

• 1.5mm Aluminium Roof Edge Drip Trim – 3m Length -- drip trim for the exposed outer edge of the flat or green roof

• Aluminium Copings range -- parapet coping to complete the full building envelope specification

Frequently Asked Questions

What is the difference between the deck version and the parapet version?

The deck version is installed in the roof deck surface over a deck-level drainage outlet. It provides access through the substrate or surface finish layer to the drain below. The parapet version is installed into the parapet wall to access a drainage outlet at the wall base. On a green roof, use the deck version for deck-level roof drains and the parapet version for outlets that exit through the parapet wall. The 450mm parapet version is available from the same range.

What depth do I order for a green roof installation?

Measure the vertical distance from the roof deck surface to the top of the drainage outlet or drain body below. Select the depth that matches this dimension. A 200mm depth is standard for most domestic green roof configurations. Use 250mm or 350mm for deeper insulated warm roofs or intensive green roof build-ups where the drain body is lower relative to the deck surface. If uncertain, measure the drain depth on site before ordering as this is a made-to-order non-returnable product.

Does the chamber need to be installed before the substrate layer on a green roof?

Yes. The deck inspection chamber must be positioned over the drain before the substrate, growing medium or drainage layer is laid. Once the chamber is in position, the build-up layers are completed around the chamber sides. The cover height should align with the intended finished substrate surface level. Installing the chamber after the substrate is laid would require removing the substrate at the drain position, which disturbs the growing medium and the filter membrane.

When should I choose 450mm x 450mm rather than 300mm x 300mm?

Use the 450mm chamber when the drainage outlet is larger than standard, when a deeper or more complex substrate build-up requires more working space, when the project specification calls for the larger chamber, or when the maintenance access specification requires a 450mm opening for operative access. For standard domestic green roof drains in moderate build-up depths, the 300mm x 300mm deck chamber is normally adequate.

Can the cover be powder coated to match the green roof accessories?

Yes. Specify the RAL colour at order and the chamber and cover are powder coated in the same external grade polyester finish. For a coordinated finish, order the inspection chambers in the same RAL as the retention trims, drip trims and any parapet coping on the same building.

Ready to Order?

Select the depth matching your drain configuration from the dropdown above, choose your RAL colour, and add to basket. For depth advice, drain layout planning, or a quote for the full green roof accessory package including retention trims and drip trims, contact our team at sales@onlinemetalstore.co.uk or call +44 7907 239290, Monday to Saturday 6:30am to 4:30pm.

Custom Fabricated Item: Made to order at our Chelmsford facility. Confirm depth before ordering. Non-returnable unless faulty. See our Refund and Returns Policy for full details.