DAIRY PLANT DESIGN AND LAYOUT

Module 5. Building construction materials and type of building construction

Lesson 29
STRUCTURAL ASPECTS OF FOUNDATIONS, ROOFS, CEILINGS, WALLS, DOORS AND WINDOWS

29.1 Introduction

Structural aspects of dairy building are very important as it is necessary to design the plant considering strength and vibrations of machines. The design aspects of roofs, ceilings, walls etc. are carefully designed to maintain required hygienic conditions in the plant. The basic principles of design of dairy building are the same as that of normal factory building. Adequate care is necessary to consider sanitary aspects while designing and selecting building materials.

29.2 Foundation

Foundation of building should be strong enough to support super structure and to resist vibrations and impact load of heavy machineries. The design of foundation depends upon the nature of structure which they have to carry and the properties of soil the soil. The structure may consist mainly of load bearing columns/walls which are required to support the structure. It is necessary to work out the total load to be supported. The actual design of foundation is based on these aspects as well as the quality of sub-soil.

29.2.1 Traditional strip foundation

This is the most usual variety and consists of concrete say 9 inches thick laid at the bottom of the trench 3 feet deep. The width that the concrete extends beyond the faces of the wall depends upon the bearing capacity of the soil. It is necessary to follow standard guidelines to decide the width of the concrete. These aspects depend on the local soil conditions as well as factor of safety to consider in the design of the building. It is not possible to generalize the design aspects of foundation. There are regions where the traditional foundation with load bearing wall is not recommended owning to soil conditions reveling in that area. Column and beam type of structure may be required to support the load and other stresses.

29.2.2 Stepped foundation

The foundation of building should be strong enough to support the superstructure. The size of foundation is governed by its depth and width which are determined by the soil type and load acting on it. The size of the foundation should be determined on the basis of bearing pressure of the soil in which it is built.

A typical section of stepped foundation for 13.5 inch thick wall is shown in Figure 29.1

Fig. 29.1 Section of stepped foundation

29.3 Walls

Walls for plant buildings are made of brick, concrete, concrete block, aluminum and glass. Bricks are widely used for the construction of walls. It is relatively cheaper and proper plastering and painting makes the walls quite water proof. In many sections, glazed tiles are laid up-o the height of 7 feet or more for ease of cleaning. With adequate care, repairs can be made without spoiling the appearance of the building.

Concrete walls are relatively costly and repairing is difficult. Provision is necessary to tackle the need of unsightly repairs. Aluminum partition walls can be made using flat panel construction or corrugated sheets. Glass panels used in building give good lighting but it is essential to keep the glass surfaces clean.

Walls which are made up of brick or stone are mainly two types.

• Partition wall: To divide an area into two or more compartments or cabinets, etc. The width of partition wall using standard brick is about 4”.
• Load bearing wall: Walls which can take loads of structure of ceiling or of superstructure. The width of the load bearing wall using standard brick is 14” or 9”.

29.3.1 Construction of brick walls

The dairy buildings are of two types namely single or two storey building having load bearing walls. Another type of building is having column and beams which supports the entire load of the building. The load of the building is transferred to the soil by beam and columns. It may be multi-storied building or even single storied building. In this case, walls are simply dividing the area in to different portions/sections. The strength of wall is not much important as the entire load is taken by beams and columns. If the size of room is small in case of load bearing structure, beam is not required. The external walls take the load and transfer it to the soil. In construction of walls using bricks, it is desirable to staggered the joints. Mortar of suitable proportion of cement to sand ratio is recommended for different types of walls. Optimum quantity of water is necessary in the mortar for proper spreading and setting of plaster.

29.3.2 Surface finishing for walls

Plastering using cement to sand ratio of 1:2 or 1:3 is used for surface finish of walls. The plaster is generally applied in two coats (1) floating coat and (2) finished coat. The floating coat of the plaster is 1.5 to 2.0 cm thick. The main purposes of plastering are as follows.

• To hide irregularity of walls (grooves)
• To avoid unevenness of wall during construction
• To improve the appearance of the wall
• It provides or facilitates the application of suitable paint
• It also prevents deterioration and protects the wall from external atmospheric effect.

Ceramic glazed tiles/vitrified tiles are also used for the purpose of wall finish.

29.4 Ceramic/Glazed Tiles

Glazed tiles are laid up to the height of 2 m in the processing room and other sections of dairy plant. The use of glazed tiles provides a surface which can be easily cleaned and hygienic conditions can be maintained. These tiles also make the wall waterproof.

29.4.1 Classification of tiles

• Non – vitreous: Non-vitreous tiles has a high degree of moisture absorption greater than 7% of the weight of the tiles. Even though, it does not prevent the tiles from having high degree of strength and it also facilitates installation because of their adherence to the mortar.
• Semi-vitreous: These tiles have a high density that limits the moisture adsorption to 3-7% of the weight of the tiles.
• Vitreous: These tiles have a moisture absorption of 0.5 to 3.0%.
• Impervious: These tiles are the hard and their moisture absorption is less than 0.5% and they are readily cleaned off stains and dirt.

In lower portion of the wall of RMRD and cold store, damage may occur. Skirting is provided in the processing room to make lower portion of the wall hard. Bumper rails in cold store and railing on the walls are provided to prevent the damage due to crates/cans. Wherever walls are not covered with tiles, they are plastered and painted. Use of good quality paint is recommended for painting of walls.

29.5 Doors and Windows

Doors and windows are subject to grueling condition existing in milk plant. The door of stainless steel is the best choice in many dairy plants. Hard wood or water proof plywood may be used for making doors and windows. Aluminum or aluminum alloys can be used but the alkaline cleaning materials which are used in milk plants may spoil the surface. Doors of ordinary steel sheet on a steel base are sometimes used, but in such cases, the whole door must be galvanized or protected against corrosion.

Plastic sheet can be used with a wooden or metal frame. There are many options available for the selection of doors and windows. It depends on the requirement, cost, maintenance etc.

Doors for cold rooms must be thermally constructed from timber/PUF panels and cladding of S.S. may be used for protection of insulation. All door fittings should be of rust proof material and of robust construction, particularly in case of swing doors. The locking mechanism for cold store room doors must always be such that it can be operated from inside the cold room.

29.5.1 Doors

The provision of doors in a building should be carefully made considering the movement of materials, persons, location of door, size requirement, type of door etc. The height of the door should be more than 2m inside the frame. Regarding the width of the door, it should be designed for the particular requirements. Usually, it varies from 0.75 m to 1.5 m depending on the type of the room. When the width is more than 1 m, double shutters may be used. The normal height of door is 2 m but it may be more in case of workshop, boiler room and garages. A rolling shutter may be used for large size doors especially in boilers, garages and workshop. The number of doors depends on the type of room and size of the room. Hardwood or laminated plywood may be used for preparation of doors. Wood or plywood doors should be protected from moisture and water by painting.

29.5.2 Types of doors

• Ledged door
• Ledged and braced door
• Frame and ledge door
• Frame and paneled door
• Louvred door
• Flush door
• Door without hinges
• Sliding door
• Rolling steel door
• Collapsible door
• Revolving door

Flush doors are manufactured in standard sizes to facilitate mass production. It consists of a skeleton or hollow frame of rails and stiles covered with plywood or any other type of reconstructed wood. Louvered doors maintain free flow of air and also maintain privacy. The door without hinges such as sliding door, rolling door etc. are used in large size doors.

29.5.3 Wnidows

The purpose of providing windows in building is to get ventilation and natural light. Openable windows provide both air and light, while non-openable windows provide only light. The size of window and its location are very important to achieve optimum advantage. In deciding the location of windows cross ventilation is kept in mind for office building. Fixed glass windows are also provided in dairy building to get natural illumination. It is recommended that

1/10^th of the floor space is allowed for the window, of which one half should be capable of opening, when required. Another thumb rule adopted is that window area is equal to the square root of the cubic contents of the room.

The exact location of the windows depends also on the purpose for which the room is used. For example, in an ordinary living room, the sill of the window should be kept at about 2.5 feet over the floor level while in bathrooms or a lavatory. The window will be kept at a higher level, so that even when the shutter is open, there should be privacy to the occupant. The window sill should be at a height of about 0.8m height from the floor. The height and width of the window depends on the type of window and number of windows. Entry to dust and insects should be prevented in the product processing room by providing a wire mesh. Total window area may be 20-25% of floor area.

29.6 Roofs and Ceilings

The use of R.C.C.is widely used for roofs and ceilings. The R.C.C. is designed and executed properly to prevent leakage of water. Water proofing work is necessary to eliminate the chances of water penetration in the R.C.C. Use of good quality materials and proper workmanship during R.C.C. work is necessary to get better result. It is necessary to carry out curing of R.C.C. immediately after setting of the R.C.C. White ceramic/glazed tiles may be laid on the terrace to reduce the heating effect and to make the R. C. C. water proof. It depends on the local weather conditions to decide the need of water proofing requirements.

Slope is provided on the top to facilitate drainage of water. The thickness of the slab varies from10 cm to 15 cm depending on the size of the room and other structural considerations. Height of processing section is more in order to facilitate the service pipelines.

Roofs are classified as flat, semi-steep and steep depending on the slope provided. Flat roofs have rise from zero (level) to 8 inches per horizontal foot. The rise in semi-steep roofs varies from 3.25 to 12 inch rise per horizontal foot. The rise of steep roofs varies from 13 to 24 inch rise per horizontal foot. In many factories and food plants roofs are generally flat or semi-steep type.

The roof sheet of different materials such as PVC, fibre glass (FRP), polycarbonate etc. in various design are available for making roof of factory. These materials have advantage of light in weight and colour choice based on the requirement of the plant. Construction of a satisfactory roof is possible only when high standards are maintained during all phases of its construction. The selection of material for roof mainly depends on the weather conditions of the place. There are options available to select the best possible roof for the plant. Ceilings of the dairy plant must be smooth and impervious so that it can be easily cleaned and maintained. In the plants where air ducting is necessary, it is carefully planned with false ceiling of appropriate material.