Whole life costing: Industrial Doors

Introduction

Industrial doors, such as those found in warehouses and storage facilities, have to meet many performance demands. Key durability issues relate to:

• Operational and mechanical performance - that is, the number of opening and closing cycles for a defined reliability level before maintenance and the costs of interruptions become excessive.

• The capacity of the finishes and materials of construction to withstand the causes of weathering and use.

Standards

There is a suite of European standards that makes it easier to specify industrial doors that meet those functional requirements. These are:

• Wind load performance: BS EN 12424 identifies six classes of wind load resistance from 0 to 5. The higher the class number the greater the wind loads a door can resist.

• Resistance to water: BS EN 12425 specifies four classes of resistance to water penetration. Typically industrial doors are Class 1, which is tested with 15-minute water spray at 30 Pa and Class 2, which is tested to resist a 20-minute water spray at 50 Pa.

• Air permeability: BS EN 12426 classifies the air permeability of doors. The seven Classes run from 0 – 6. The higher the class, the lower permeability. A Class 1 door has a permeability of 24m˛/m˙h at 50 Pa. Each Cclass as a permeability rate half that of the previous Class.

• Safety: BS EN 12453 defines safety requirements for power-operated doors. Hazards and risks are identified - for example, crushing hazard between the door leaves and perimeter of opening. Safeguards, design strategies and criteria for avoiding hazards are listed.

• Mechanical requirements and operational durability: BS EN 12604 specifies the mechanical requirements for industrial doors, such as strength and the factor of safety.This standard is important in assessing potential durability, as it requires manufacturers to state the number of cycles doors have been tested to. Durability is judged by reference to the economic life of the door - in other words, when the costs of maintaining the door are greater than the cost of door replacement.

• Installation and use: BS EN 12635 covers installation and use of industrial doors. This includes the identification of maintenance and repair activities which are essential for life cycle management and planning.

Other issues

Design issues such as thermal, fire and sound performance should be addressed, as well as security. Wet internal environments will affect specification and durability. Other issues that directly affect durability include the operating speed of the door, the frequency and intervals between operations and who the users are.

Specification options

Door types

• Vertical overhead sectional doors. In the most common arrangement, the door leaves slide up under the roof.

• Horizontal folding doors. These incorporate sections like vertical overhead sectional doors but open horizontally.

• Roller shutter doors. These consist of metal laths which roll up around a high-level barrel above the door opening.

Material options

• Sectional and folding doors may be non-glazed, part-glazed or fully glazed. Single or double-glazed options are available in acrylic or toughened glass.

• Sections or roller shutter laths are usually made from aluminium or low carbon steels, which may be filled with an insulating material for enhanced thermal performance. Stainless steel components may be used for extremely corrosive environments.

• Steel doors have a corrosion protection layer, usually zinc (Z275g/m˙) or zinc–aluminium (ZA255g/m˙). Aluminium may be left mill-finished.

• Decorative coatings for both aluminium and steel include PVC Plastisol (durability 10 to 30 years), polyvinylidene fluoride PVF2 (10 to 15years), polyester (5 to 10) years, polyurethane (10 to 15years). Life expectancies are the period to the first maintenance. Life depends on exposure to coastal, polluted or industrial environments, aspect and orientation, as well as the coating thickness.

Method of operation

• Manual doors are typically operated by means of a chain hoist. Doors larger than 4m x 4m need to be operated electrically because of their weight.

• Power-operated doors may be triggered by a variety of controls including: push button, pull rope, remote control, magnetic loops, photocells, radar and even mobile phones.

Specification options

Table notes

• Costs are for installation of doors only, ancillary work such as electrical supplies and preparation of surround not included. Through life costs include replacement, annual servicing, minor repairs, and recoating finish.

• Steel doors: Steel to BS EN 10326, ≥0.4mm thick, all galvanized to Z275g/m² minimum. Aluminium to BE EN 485, ≥0.6mm thick. Sectional steel doors twin skinned, insulated, minimum 40mm thick.

• Expected service lives are 20 years for all doors and relate to 20,000 operational cycles with two opening and closing cycles a day on average.

•A discount rate of 3.5% is used to calculate net present values.

• Door types are not directly comparable as sizes vary. A cost analysis based on project specific information is essential for a realistic best value appraisal.

First published in Building 2005

Further information

BLP provides latent defect warranties for buildings www.blpinsurance.com

Further information contact peter.mayer@blpinsurance.com or telephone: 020 7204 2450