The design and construction of food premises

A well-planned layout and the use of satisfactory building materials are essential to achieve high standards of hygiene. The size of the premises must facilitate efficient operation and the site must be large enough to accommodate possible future expansion.

Selection of a suitable site:

The site must have sufficient services, i.e. electricity and gas, water supply and effluent disposal, and be accessible for delivery and waste disposal. It should not be liable to flooding or unacceptable contamination from chemicals, dust, odour or pests. Potential for noise emissions should be considered if there are nearby residential premises.

General principles of design:

To achieve a satisfactory design, the following principles should be considered:

• clean and dirty processes must be separated to minimise the risk of contamination. Colour coding may be used. Where possible:
  • work areas should be segregated into pre-cook and post-cook; and
  • a separate area should be provided for de-boxing and unwrapping raw materials
• workflow should be linear and progress in a uniform direction from raw material to finished product (from dirty to clean). This is essential to minimise risk of cross-contamination. Distances travelled by raw materials, utensils, food containers, waste food, packaging materials and staff should be minimised;
• facilities for personal hygiene and disinfection of small items of equipment should relate to working areas and process risks;
• where appropriate, suitable facilities must be provided for temperature, humidity and other controls;
• the premises must be capable of being thoroughly cleaned and, if necessary, disinfected at the end of production;
• insects, rodents and birds must be denied access and harbourage;
• yard surfaces and roads within the boundary of the premises must have a suitable impervious surface with adequate drainage, and provision made for refuse storage; and
• suitable provision must be made for staff welfare, including cloakroom and, if necessary, canteen and first-aid facilities.

The Construction of Food Premises:

It is essential that the correct materials are chosen for all internal finishes and that they are properly fixed or applied. Materials should be non-toxic, durable and easy to maintain and clean. Flaking paint, for example, from ceilings and walls is a potential physical contaminant of food. Gaps or holes in walls and ceilings allow pest entry and harbourage, and act as dirt traps. Uncovered light fittings pose the risk of glass contamination of food.

Ceilings

Suspended ceilings are advantageous as horizontal pipework and services can be concealed in the ceiling void. They are normally constructed from a metal lattice incorporating cleansable panels. Aluminium backed and faced fibreboard has proved successful in many food factories. Flush-fitting ventilation grilles and lighting will often be provided.

Solid ceilings should be well insulated (to prevent condensation and mould growth), smooth, fire-resistant, light-coloured, and coved at wall joints. Finishes should be washable. A non-flaking emulsion may be suitable. Special attention must be paid to ceiling finishes above heat and/or steam-producing appliances such as ovens, sinks and retorts. Canopies and separate extraction units may be fitted in these areas. Ceiling height will vary depending on the type of operations being carried out but should be high enough to provide satisfactory working conditions and allow the installation of equipment.

Walls

Smooth, impervious, non-flaking, durable, light-coloured wall surfaces are required which must be capable of being thoroughly cleaned and, if necessary, disinfected. Dark coloured wall surfaces do not reflect light and dirt is more difficult to see. Internal solid walls are preferable to those with cavities.

When constructing factories, it can be advantageous to use modular buildings, of standard dimensions, with the actual production areas built inside the external structure, leaving clear walkways outside these areas, but within the overall structure. The ‘building within the building’ can be fabricated from modular panels of the type used for cold-store construction.

Wall surfaces in use include resin-bonded fibreglass, ceramic-faced blocks, plastic panelling, epoxy resin, glazed tiles with water-resistant grouting and rubberised paint on hard plaster or sealed brickwork. Some paints incorporate a fungicidal additive. Galvanised steel, aluminium and stainless steel are also used, and plastic sheeting is popular. Wall or floor stops are needed to prevent doors damaging wall surfaces, and wall corners should be protected. Crash rails should be used if trolleys are likely to damage wall surfaces, although large, angled fillets to the wall-floor junctions can also prevent trolley impact.

Pipework and ducting should be bracketed at least 150mm from walls to facilitate cleaning. All lagging to pipes must be smooth and impervious. Pipes passing through external walls must be effectively sealed to prevent the ingress of pests.

Windows and doors

Any windows should either be fixed on north-facing walls to reduce glare and solar heat gains, or treated with solar film to counteract heat gain. Openable windows are required to improve ventilation and reduce condensation. Cleansable, well-fitting fly-screens must, where necessary, be fitted to opening windows. Windows should be constructed to facilitate cleaning and any internal window sills should be sloped to prevent their use as shelves.

Doors should have smooth, non-absorbent surfaces capable of being thoroughly cleaned. They should be tight-fitting and self-closing. Door handles and finger-plates should be capable of disinfection. Swing doors with kick-plates are preferable to handles. External doorways should, where necessary, be proofed against the entry of insects, and metal kick-plates should be provided to prevent gnawing by rodents. Clear plastic strips can be used to protect openings.

Floors

Regard must be had to initial cost, durability, performance and safety. In food premises, floors should be durable, non-absorbent, anti-slip, without crevices and capable of being effectively cleaned. Where appropriate they must be resistant to acids, grease and salts and should slope sufficiently for liquids to drain to trapped gullies or channels; a slope (or ‘fall’) of 1 in 60 is the minimum recommended. The junctions between walls and floors should be coved.

Suitable flooring includes epoxy resin, granolithic (concrete incorporating granite chippings), welded anti-slip, vinyl sheet and slip-resistant ceramic or quarry tiles. Untreated concrete is unsuitable as it is porous, dusty and difficult to clean.

Cardboard or sawdust should not be placed on floor surfaces as it absorbs grease, moisture, bacteria and dirt. Sawdust can be blown onto food and cardboard causes a trip hazard.

Services

These include gas, electricity, water supplies, drainage, lighting and ventilation.

Gas supplies

Supply pipes should always be mounted clear of the floor and never so close to other pipes as to restrict access for cleaning. Flexible connections, to facilitate removal of equipment for cleaning purposes, are recommended.

Electrical supplies

Adequate numbers of power points should be available for all electrical equipment. Cut-out switches for power circuits should be accessible and separate from lighting and ventilation supplies, so that cleaning can take place in safety. Separate cut-out switches should be provided for refrigeration equipment.

Controls should be fixed clear of equipment to avoid becoming dirty or wet during cleaning. Removable electrical components assist cleaning and are advantageous. Surface-mounted electrical wiring should be protected by waterproof conduits. All switches should be flush-fitting and waterproof (especially in production areas).

Water supplies

Cold water supplies for use with food, for cleaning equipment or surfaces or for personal hygiene must be potable (of drinking water standard). They should not be fed via an intermediate tank unless chlorinated; mains supplies are preferable.

Water heating provisions should be able to supply hot water at a target discharge temperature of 60°C, although higher system temperatures may be required to avoid legionnaires’ disease. In this case, mixer taps will be needed to avoid scalding. In hard- water areas, provision for softening should be made.

Non-potable water must be conveyed in identifiable systems which have no connection with, nor any possible reflux into, the potable water system. An external water supply should always be available.

Drainage

Premises should have an efficient, smooth-bore drainage system. Drains and sewers should be adequate to remove peak loads quickly without flooding. Sufficient drains should be installed to facilitate effective cleaning of rooms by pressure jet cleaners or other means. Channels or trapped gullies may be used. Grease traps, if fitted, should be large enough to allow adequate time for fat to separate and should be emptied regularly.

The direction of flow should be from clean areas to dirty areas. Toilets should feed into the system after food rooms. Inspection chambers should be placed outside food rooms but if interior location is unavoidable, they must be airtight, i.e. triple seal, bolt down. All drainage systems must be provided with sufficient access points to allow rodding in the event of blockages. Petrol interceptors may be required for yard drains.

Drains should be constructed to inhibit the harbourage and movement of vermin. All external rainwater fall-pipes should be fitted with balloon guards to prevent rodent access. Circumference guards should be fitted around all vertical pipes fastened to walls, to prevent rodents climbing up them.

Ventilation

Sufficient ventilation must be provided to produce a satisfactory, safe working environment and to reduce humidities and temperatures which would encourage condensation and the rapid multiplication of bacteria. Condensation encourages mould growth and the multiplication of bacteria and drips onto food. Normally, ambient temperatures should be below 25°C. Natural ventilation often needs supplementing by mechanical ventilation to ensure effective air circulation and adequate air changes. You cannot rely on open windows. Extract ventilation should always flow from a clean to a dirty area. Its function is to prevent excessive heat build-up, condensation, dust, steam, and to remove odours and contaminated air. The source of input air must always be checked to ensure contaminants are not brought in to food rooms. Steam-producing equipment, such as cookers, boilers and blanchers, should be provided with adequately-sized canopies. Provision of lower heat-emitting equipment such as pressure vessels and microwave ovens, and upgrading insulation on ovens will reduce heat production.

Lighting

Suitable and sufficient lighting must be provided throughout food premises, including store rooms, passageways and stairways, so that employees can identify hazards and carry out tasks correctly.

Artificial lighting is often preferred to natural lighting because of problems of solar heat gain, glare, shadows and flying insects entering open windows. Recommended illumination levels are as follows: 150 lux in storerooms and 500 lux in preparation areas. Fluorescent tubes, fitted with diffusers to prevent glare and product contamination in the event of breakage, are recommended.

Handwashing facilities

Adequate facilities for handwashing and drying should be provided wherever the process demands. In particular, a suitable number of basins or troughs should be sited at the entrance of food rooms to ensure all persons entering wash their hands. Washbasins must be easily accessible, should only be used for washing hands and should not be obstructed. All basins and troughs, preferably made of stainless steel, should be connected to drains by properly trapped waste pipes. Washbasins should be clean and provided with hot and cold water, liquid soap, drying facilities and a sign indicating that they are for handwashing only. They should not be used for any other purpose. A clean nailbrush may also be provided. Mixer taps are preferable so hands can be washed under warm running water. Non-hand operable infrared taps are preferred as they reduce the risk of cross-contamination. Hand washbasins should be sited to avoid water from the washing of contaminated hands spraying onto uncovered ready-to-eat foods.

Cleaning and disinfection facilities

Where appropriate, adequate facilities for the cleaning and disinfection of utensils, crockery, cutlery, glasses and equipment should be provided. These facilities will normally be constructed from stainless steel. Twin sinks are preferable to facilitate washing and disinfecting/rinsing. Sinks should be freestanding so that they can be removed easily after unscrewing the lower trap joint, freeing the waste pipe. ‘Sterilising’ sinks and units should be capable of operating at 82°C.

Separate sinks must be provided for food preparation and equipment washing if the volume demands it. In small operations the same sink may be used if there is no risk to food safety. Exclusive food sinks may be provided with cold water only. Washing machines should not be sited in kitchens as this will involve bringing soiled and contaminated laundry into the kitchen. In the case of small nursing homes and guest houses this may even involve bedding and towels contaminated with body fluids. Laundry rooms should always be kept separate from kitchens to avoid the risk of contaminating food.

Sanitary conveniences and washing facilities

All new premises should be provided with adequate staff sanitary accommodation, adequately ventilated and lit. They should be kept clean and tidy. Rooms containing sanitary conveniences must be readily accessible but must not communicate directly with a room where food is processed, prepared or eaten. Internal wall and floor surfaces should permit wet cleaning.

Foot-operated flushing devices are recommended. Doors to intervening spaces and sanitary accommodation should be self-closing and clearly illustrate the sex of the user. Suitable and sufficient washing facilities must be provided at readily accessible places. In particular, facilities must be provided in the immediate vicinity of every sanitary convenience and supplied with clean, hot and cold or warm water, liquid soap and appropriate drying facilities.

Cloakrooms and lockers

Adequate accommodation for outdoor clothing and footwear, not worn by the staff during normal working hours, must be available. Such articles must not be stored in a food room unless in suitable cupboards or lockers provided only for this purpose. Adequate facilities for drying wet clothing should also be provided. Cloakrooms must be kept clean and tidy as scraps of food and other materials may attract cockroaches and rodents.

The storage and disposal of waste

Waste disposal systems must be planned, along with other services, when food premises are designed. Refuse collectors should not have to enter food rooms or dining areas.

Waste food should be kept separate from paper and cardboard packaging. In some instances, waste may be stored under refrigeration pending collection, for example, bones in butchers’ shops. It is preferable for all waste food to be removed from food premises at least daily and general refuse to be removed at least twice a week. Accumulations of refuse in food rooms are illegal, attract pests and encourage the multiplication of bacteria. They create odours, prevent effective cleaning and expose food to risk of microbiological and physical contamination. Suitable, impervious, easy-to-clean containers with foot-operated lids should be provided in food rooms. Disposable plastic sacks are also ideal. Regular emptying of internal waste bins is important, even if the bins are not full. This will reduce unpleasant odours, maintain adequate capacity and minimise bacterial multiplication and insect problems, for example, from maggots. Hazards that result from poor waste storage include:

• the attraction/multiplication of pests;
• the contamination of food (microbiological, chemical or physical); and
• the multiplication of bacteria.

Suitable facilities must be provided for the storage of waste externally, prior to removal from the establishment. Dustbins or bulk containers are commonly used, although skips and compactors are more appropriate for food factories. Compactors vary from units similar to a large dustbin to refuse-sack compactors and skip rams.

Dustbins should be stored clear of the ground, for example, on tubular steel racks, to facilitate cleaning and removal of spillages. All receptacles should be capable of being cleaned and provided with suitable tight-fitting lids or covers to prevent insects, birds and rodents gaining access. Overflowing bins attract pests.

The refuse area must have a well-drained, impervious surface which is capable of being kept clean. Standpipes, hoses and, possibly, high-pressure sprayers should be provided for cleaning purposes. Covered areas to protect refuse from the sun and rain are recommended. Satisfactory provision should be made for the disposal of liquid food waste such as oil. Refuse areas should be secure and not be too far from food rooms to discourage their use but they should not be too close to encourage flies to enter the food rooms. They should not be sited next to the main food delivery entrance. Covered ways between refuse areas and food rooms are useful to protect staff against inclement weather. 

Perimeter areas

It is recommended that a concrete path, at least 675mm wide, abutting the external walls should be provided around all food buildings. This removes cover for rodents and enables early signs of pests to be discovered, for example, rodent droppings. Paths should be kept clean, free of vegetation and inspected regularly. A smooth band of rendering, around 450mm, at the base of external walls will discourage rodents from climbing. Whenever possible, a perimeter fence should be constructed around food premises to deter unauthorised entry. Areas within perimeter fences must be kept clean and tidy. Rubbish, old equipment and weeds must not be allowed to accumulate or provide harbourage for insects or rodents.

Kitchen design

The layout of a well-designed commercial kitchen has three main characteristics:

• clearly identified and separated flows;
• defined accommodation, specific to the purposes allocated; and
• economy of space provision (commensurate with good hygiene practice).

The unit should also afford management personnel easy access to the areas under their control and good visibility in the areas which have to be supervised. Space is needed for management function and for equipment such as telephones and computers.

Flows

Four separate flows need to be considered: the food being produced; personnel; containers, utensils and equipment; and waste/refuse. Product flows should be subdivided into high-risk and contaminated (raw food) sections. Clear segregation should be maintained between the two. As far as practicable, flows should be in one direction without backtracking or crossover from ‘dirty’ to ‘clean’ or from ‘low-risk’ to ‘high-risk’.

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