Specifying Metal Planters for Super-Prime Residential

A review of the singular challenges faced when specifying planters for the Super-Prime Residential market

The Super-Prime Residential market is one in which IOTA has considerable experience, and relevant projects include:

• Chelsea Barracks, London SW1 >>
• Buxmead, The Bishops Avenue, London N2 >>
• The Glebe, Chelsea, London SW3

Super-Prime Residential developments will require exacting standards of manufacturing quality and finish – this is, of course, to be expected. Additional design and specification challenges will include some combination of:

• Planting schemes will likely be highly ambitious [complex, large in scale and with mature specimen planting], and planter design, specification and fabrication have to be ‘up to the job’. The planters may well require design, technologies and skills more akin to architectural and/or engineering metalwork, rather than what is normal within the landscape industry.
   
• Planter design will often include complex additional functionality [such as lighting, automatic irrigation systems, drainage plans etc.]; and there is also likely to be integration between the planters and non-landscape structural elements of the build, further increasing design complexity and contractual liabilities.
   
• Logistical challenges [such as craning onto / over roofs] may need to be designed-in, ideally as early as possible within the design process. If this issue is overlooked, then retrospective solutions to logistical problems can prove extremely costly.
   
• Contractual structures tend to be complex. For example: there will almost certainly be a ‘vision’ developed by award-wining garden designers and client architects, which needs to be translated into constructional planter designs and specs. And there will be multiple contractors and other professionals [such as structural engineers] involved.

Thus planters for Super-Prime Residential are certainly ‘outside the norm’, as can be seen in some of the design drawings and images shown here.
 

Value-Engineering and Material Specification

With Super-Prime Residential projects, it is also almost inevitable that there will be extensive, reiterative design Value-Engineering [VE] processes.

The cold, commercial truth is that planters are not the top of any developer’s list of priorities. Final decisions on planters will be taken late in the total build programme: by which time prior budgets will already have been over-spent on elements of higher perceived value; and there will be strong pressure to reduce costs on all elements of the landscape package, including the planters. During VE, there will be limited options to reduce the scope of works; as the landscape vision will already have been sold to prospective clients, and – arguably as/more importantly – to planners.  Thus, in all likelihood, VE discussions will focus on material specification, this being one of few VE levers available.

With the material specification of metal planters in Super-Prime Residential developments, the central issue is one of warranties. The properties will be sold by the developer with extensive warranties; a liability that the developer will seek, understandably, to collateralise down the contractor chain. However the only way to get a cast-iron, third party-underwritten warranty for 25+ years on a metal planter is to make it from 316-grade Stainless Steel, and few developers will pay that premium. Therefore, in IOTA’s experience, VE discussions will end up deciding to spend the available budget on Zintec [Zinc-Plated Steel] or Mild Steel with an extremely high quality paint finish, underpinned by normal commercial warranties.

This option offers the best ‘bang-for-the-buck’, with a significant saving off Stainless Steel. And the option is safe to specify in Super-Prime Residential developments, as they can afford the kind of inspection and maintenance programmes necessary to ensure extreme longevity from a paint finish.

Polyester Powder Coating [PPC] technologies have advanced dramatically in the last 20-30 years, and there are now a huge variety of coatings available, from PPC manufacturers such as Akzo Nobel, IGP and Syntha Pulvin. Each have their own brands, and application systems – but the essential specification requirement is to state that:

The PPC coating and application system used must ensure extreme longevity in C3/C4 environments – defined as:

• C3  Urban and industrial atmospheres with moderate sulphur dioxide pollution
• C4  Industrial areas and costal areas with moderate salinity

Two such systems commonly used by IOTA in these circumstances follow a 3-coat system with coating products from Akzo Nobel, which might be used as example specs. – these comprise: 

Option A

Material: Mild Steel
Pre-treatment: Blast Cleaned SA 2.5
3-Coat application:

1. Zinc Primer: Interpon PZ 790
2. Intermediate/Primer: Interpon BPP 330
3. Topcoat: Interpon D1036

Option B

Material: Zintec [Zinc-Plated] Steel
Pre-treatment: Degrease and Abrade
3-Coat application:

1. Primer: Cromadex 903 Etch Primer
2. Intermediate/Primer: Interpon BPP 600
3. Topcoat: Interpon D1036

The above are also the PPC systems recommended and used by IOTA for Coastal Locations >>

Finally, these kinds of complex, high-performance PPC systems are only as good as their application. Thus it is important to specify that PPC application must be in-house, and/or from an accredited PPC facility, familiar with these systems and with demonstrable track record.