Partitions and Suspended Ceilings

Partitions

Advantages of partition

• Divides the whole area into number of rooms,
• Thin in section and therefore occupy less floor area,
• Offers privacy for both sight and sound,
• Easy in construction in any position.

Requirements of good partition

The good partitions should be such that it should be

• Thin in section to utilize maximum floor area
• Provide adequate privacy in rooms for both sight and sound
• Use of durable, light and strong material
• Simply, easy and economical in construction
• Fire resistant
• Heat and damp resistant
• Resistant to insect and fungus attack

Types of partition

According to nature of loading condition  these can be classified as load bearing and non- load bearing partitions.

1. Load bearing partitions:

These are designed and constructed to receive superimposed loadings and transmit these loads to a foundation. It supports the joists the joists of the floors (i.e. suspended floor), purlin and ceiling joist of the roof. Generally load bearing partitions are constructed of bricks or blocks bonded to the external walls. Lintels are used to span openings.

2. Non-load bearing partitions:

Non-load bearing partitions neither receive superimposed loads nor transmit any structural loads to the structural members below. This partition has only own weight to hold in position. It also carries fixtures and fittings necessary in the room. It is obvious that it must be able to resist impact loading on its face and also vibration caused from any reason.

Types: According to use of materials

1. Brick partitions

• Plain brick
• Reinforced brick(after 4/5 layers)
• Brick noggin (bricks in wooden frame)

2. Glass partitions
3. Concrete partitions
4. Metal lathe and plastered partitions
5. AC sheets or CGI sheets partitions
6. Hollow block partitions
7. Aluminum partition
8. Timber partitions

• Stud or common partition: Horizontal members supported on roof and floor (head/sill), vertical posts, studs, boarding on both sides.
• Trusted or braced partition: Horizontal members supported into wall (head/ sill), vertical posts, studs, boarding on both sides.

9. Gypsum board partitions
10. Strawboard partition
11. PVC board
12. Fabric

Suspended ceilings

A suspended (false) ceiling is the construction below the roof/slab. Ceiling is the false structure(non load bearing) in overhead of the room below the roof. It has a framework suspended (supported) from the main structure, usually in the roof/slab and covering material is then fixed on the frame. It forms void between the ceiling and the roof/slab. This void is used for housing electricity trunk-lines, AC ducts, pipes etc. It is frequently made of wooden frames and planks are fixed on it. Metals and other materials may also be used for the ceiling. The ceilings are also covered by rails and panels in different patterns. 

 Purpose

Depending on the purpose, plasterboards, strawboards, Paris-boards etc. are also secured to ceilings. 

• Mainly provided for aesthetic reason
•  To visually conceal structural details, wiring, ducting and the sort.
•  The void space created is used to house embedded lighting systems, sprinklers, smoke detectors etc. 
• To add to the thermal/ sound insulation . 
• To lower ceiling height, hence to reduce the volume of the room and improve its air conditioning and acoustical quality. 
• To protect structural members from fire.

Requirements of suspended ceilings

• Easy to construct 
• Easy to clean, repair and maintenance
• Conform the building standards and norms of country,
• Provide adequate means of access(enough space) for maintenance for concealed services therein

Types of ceilings

1. According to use of materials

• Timber (bamboo, plywood planks etc)
• RCC
• Metal (steel, aluminum)
• Composite board
• PVC board
• Straw board
• Glass
• Paper
• Textile

2. According to construction methods

• Joint less
• Jointed
• Open

Joint-less ceiling: The ceiling that is monolithic in appearance and no joints can be seen on the surface is termed as joint less ceiling. This can be done by applying plaster on the ceiling, plaster board/ expanded metal lathing or spraying of asbestos/ vermiculite cement/ any other chemicals may be made on the metal background.

Jointed ceiling: Jointed ceilings are very commonly used. The joints on the ceiling may be made in decorative appearance. The frame is made according to the desired shape and sized ceiling boards. Ceiling materials may be fixed with spring clips or nails/ screws.

Open ceiling: In the opened ceiling, the frame is fixed in such a way that voids are formed to give virtual effect. Voids are largely provided for decorative purpose. This may be a means for acoustic absorption as well.

Procedure for ceiling fixing

Ceiling joists are fixed on desired height from the floor. If necessary, vertical struts are fixed to set joists. Battens are than fixed on the joists. Ceiling materials as; planks, plywood, metal sheets, etc. is fixed on the battens. Finally, painting and finishing is done.

Joints and its types in Building Construction

 Joints

Usually buildings are large and need to be constructed part by part. The points of connection are termed as the joints in a building. Joints are unavoidable. It is because, the materials of constructions may not be available to the required dimension. The effect of weather and thermal phenomena has also serious consequence on the bulk volume of the work. All these facts call for the provision of joint in construction work.

The need of provision of joints:

• Between different materials in composite structure
• Between the same materials with different parts requiring different fabrication timing
• To allow space for shrinkage and expansion due to thermal and moisture movements 
• To control cracking due to the possible structural movements of the fabric.

Types of Joints

The various types of joints in a structure are;

1. Expansion Joint
2. Isolation Joint
3. Contraction Joint
4. Sliding Joint
5. Construction joint

1. Expansion Joint:

It is provided to accommodate the expansion of adjacent building parts and relieve compressive stresses that may otherwise develop mainly due to change in temperature. Expansion Joints are necessary when continuous length of a structure exceeds 45 M. The recommended maximum centre to centre spacing of expansion joints is 30 M. The gap varies from 10 mm to 40 mm. The gap is filled with compressible material for wind and water tightness as well as aesthetic.
The various materials available for treating the expansion joints are;
Joints Filler (bitumen, rubber, fibre etc.): Durable/ flexible material used to fill the gap if desired.
Sealing Compound  (bituminous sealant): These are applied in layers to seal the exposed slits against passage/ penetration of moisture, dust, etc.
Water Bars  (Rubber, P.V.C, Metallic): These are seal against passage of water.

2. Isolation Joint:

The details are similar to Expansion Joint, Where a part of a structure is higher than the other, it is desirable to separate the two structures. Isolation joints are provided to avoid damages to the structure due to differential settlement cause by varying soil pressure. It is sometimes provided in a regular structure, which has varying soil condition over its length. It is also provided to separate foundation of machines from rest of the structure.

 3. Contraction Joint (Shrinkage Joint):

The property of concrete to set and harden results in shrinkage in volume (contraction). It mainly depends on the amount of water in the mix. Contraction creates tensile stresses which may result in formation of random cracks.
Different types of Contraction Joints are
Complete contraction joint: Discontinuity of  both concrete and steel creates a complete joint.
Partial contraction Joint: Discontinuity of concrete only, creates a partial joint.
Dummy joint: These are provided in PCC/RCC pavements and flooring. The groove is of @ 3mm wide and 1/3rd to 1/5th of thickness (deep). It is normally filled with bitumen or rubber to provide a plane surface.     

4. Sliding Joint:

It is provided between part of a structure which has a sliding tendency over the other part due to variation in temperature or moisture. Example; RCC Slab and beam over masonry wall.

5. Construction Joint:

Generally casting of concrete is planned and preferred to be completed at one stretch within a day. Casting is seen to start early in the morning and are extended into late evenings, under flood lights. However, as the size of the building increases casting at a stretch becomes impossible and extends into two to three days. In such cases provisions are made for strategic location of construction joints in the cast to provide a water tight joint.

Factors to be taken into consideration during preparation of construction joints;

• Joints should be located near plane of minimum shear.
• Joints should be at right angle to the axis of the member for horizontal, vertical or inclined members.
• Prior to laying new concrete the stop-board is removed and the face is cleaned with wire brush and  water and treated with a coat of cement mortar.

Location of Construction Joints

In case of slabs:

The joint should be located at points of minimum shear, which is at mid way or with the center between support with the vertical plane at right angles to the direction of the main reinforcement. It also can be located directly over the center of the beams making a vertical joint at right to the span. The layer of concrete at joint should be finished against a properly fixed stop-board to ensure a vertical clean surface.

In case of Beams:

The joint should be located at the point of minimum shear, which is at mid way or within the center between the support, with vertical plane at right angle to the direction of main reinforcement. It can also be formed at the center of column along the vertical plane at right angles to the length of beam, allowing one half of the beam to become the bearing surface of the future adjoining beams. In no case should be concreting be terminated in beam or slab where shearing action will be greatest i.e. near the ends or directly under the concentrated loads. The layer of concrete at joint should be finished against a properly fixed stop-board to ensure a vertical clean surface.

In case of column:

These joints can be provided at a level surface 10 to 15 cm below the junction with the beams. This is particularly important in flat slab construction. Normally, two hours elapse between pouring of concrete in beams/ slabs to allow for settlement of shrinkage of the column concrete.

In case of walls:

The horizontal construction joint in walls should be located at the top of plinth, top or bottom of window opening or at any other convenient height

Methods of joining new concrete to old one:

1. If the stoppage in concreting work is for a short duration, then the joining is done by applying mortar grout of similar composition to that contained in the new concrete.
2. In case of floor and roof slabs, if the slabs are cast in section then to prevent water seepage.
3. If the surface is partially hardened, the joining surface should scrubbed with wire or hard bristle brush, removing dirt and other undesirable materials. The joining surface is then moistened with water and cement slurry (1:1) , applied with a brush followed by 150mm thick layer of cement mortar (1:2).
4. If the surface is partially hardened, the joining surface should scrubbed with wire or hard bristle brush, removing dirt and other undesirable materials. The joining surface is then moistened with water and cement slurry (1:1) , applied with a brush followed by 150mm thick layer of cement mortar (1:2).

Windows and Ventilation in Building

Windows

Window is the opening in the building. Window is a switch used for light, ventilation and visual connection usually between the outside and the inside. These are not meant for access. It rests on sill of a wall and are usually topped by lintel. It is made of different materials including Timber, Aluminum, Steel, PVC, etc. The sizes vary according to purpose and use.

Elements of Window(Terminology)

1. Frame   - It is the vertical member/ post fixed on the wall with the help of holdfast (125X75). 
2. Shutter – It is the movable part of the door which is hinged with the frame.
3. Holdfast – It is the metallic anchorage which holds the door frame against the wall.
4. Post/ jamb - Vertical member/ face of the frame/ wall, which receives the holdfast.
5. Head - The horizontal member at the top of the frame.
6. Rails – They are the horizontal members of a shutter. They are termed as the Bottom, Lock (middle), Top rail according to their location in the shutter.
7. Stile – The vertical member of shutter, which frames the shutter.
8. Panel - Block or board to seal the void of a shutter.
9. Mullion-  The vertical member lying between two shutters.
10. Sill-  the lower part of window frame.
11. Horn-  parts of window or door frame left for proper anchorage.

Types of Window

Casement/ordinary windows

A casement window is a window that is attached to its frame by one or more hinges. It usually comes in combination with fixed and ventilator portion.

Glazed/sash windows

It is the most common type of window. The window section is of glass panel. It is of two types: Single glazed, Double glazed:

Singal glazed :- It is the general practice in our locality.

Double glazed :- It is done for special purpose, such as insulation of heat and sound. Almost all glazed door and windows are double is Europe and other cold region. This in not familiar in our Himalayan region.

Louvered windows

The section is fixed with louvered. It has blind or shutter with horizontal slats that are angled to admit

light and air, but to keep out rain, direct sunshine, and noise. The angle of the slats may be adjustable. It is suitable where ventilation is desired without visual connection. 

Pivoted windows

The frame is pivoted up and down or may be horizontally or vertically pivoted along the center as per need.

Corner window

The section is fixed at the corner in two direction. It is placed at the corner, whose portion extends into both the wall.

Double hung window

The section slides vertically with in grooves in frame. It occupies less space.

Gable window

This is ordinary window. It is positioned at the gable end of the roof.

Dormer window

A dormer is a structural element of a building that protrudes from the plane of a sloping roof surface. It is placed on the roof (slope) to bring light and ventilation inside the room/attic. Dormer windows are source of light and ventilation for top floors.

Bay windows

A bay window is a window space projecting outward from the main walls of a building. It is a multi-

panel window with at least three panels set at different angles. The angles most commonly used on the inside corners of the bay are 90, 135 and 150 degrees. They are projected outside usually with low sill.

Clerestory window

It is the window just below the roof or ceiling. It is placed over the slab of a room to serve the room inside with high ceiling. Clerestory refers to any high windows above eye level. The purpose is to bring outside light, fresh air, or both into the inner space.

Lantern window

A roof lantern is a multi-paned glass structure a small building, built on a roof for day or moon light. The sections are placed horizontally on the flat roof for the purpose of light.

Sky light window

The sections are provided in a sloped surface. They are used for daylighting. The thermal performance of skylights is affected. During warm seasons, skylights with transparent glazing will cause internal heat problems.

Sliding window

In this type of window, the section slides in sideways or horizontally. It is popular in aluminum, steel and U-PVC.

Steel (metal) window 

This type of window comes in angle section/rectangular pipe section which are used as frames.

French window

This type of window has one or more panes of glass set into the whole length.

Ventilation

Ventilator is narrow opening with small height provided near the roof or slab in the building. The main purpose of the ventilation is to facilitate ventilation in the building. The shape and size of the ventilator is similar to the window sections. The shutter of the ventilator is pivoted and can be opened or closed. These shutters are side hung or top hung. They are also found as part of the door or window.

 Types of ventilators

1. Side hung

1. Bottom hung

1. Horizontally pivoted

1. Vertical pivoted

1. Top hung

1. Vertical sliding etc.

Fixing method

 According to material use, fixing of door and window frames are done simultaneously at the time of wall construction. Holdfasts of required numbers are nailed. Frame is carried to position and set with the help of ropes and poles. Frame is then put to plumb (frame should be perfectly vertical). Once the frame is set and leveled, the holdfasts are fixed in wall, cement, concrete etc. Final checking of plumb is done, if required corrections are applied.

Doors and its types in buildings

Door 

A door is a movable structure used to close off an entrance. When opened, they admit ventilation and light. It typically consists of a panel that swings on hinges or that slides or rotates inside a space. Door has essentially two parts: Frame and shutter. The door is used to control the physical atmosphere, noise, etc. Doors also have an aesthetic role in creating an impression.

Elements of Door (Terminology)

1. Frame  - It is the vertical member/post fixed on the wall with the help of holdfast (125X5). It receives the  door shutter.
2. Shutter – It is the movable part of the door which is hinged with the frame.
3. Holdfast – It is the metallic anchorage which holds the door frame against the wall.
4. Post/jamb - It is the vertical member/face of the frame/wall, which receives the holdfast.
5. Head - It is the horizontal member at the top of the frame.
6. Rails – They are the horizontal members of a shutter. They are termed as the Bottom, Lock (middle), Top rail according to their location in the shutter.
7. Stile – It is the vertical member of shutter, which frames the shutter.
8. Panel - It is the block or board to seal the void of a shutter.
9. Batten – They are the planks used for the face of a shutter. (traditional door)
10. Ledge - It is the horizontal member used in battened & ledged door. (traditional door)
11. Brace - It is the inclined member used in battened ledged & braced door. (traditional door)

Types of Door

1. Battened door
2. Paneled door
3. Glazed door 
4. Flush door
5. Sliding door
6. Revolving door
7. Collapsible door
8. Rolling shutter door
9. Swing door
10. Solid core door
11. Nuwood door

Battened door

It consists of series of battens  with tongue & groove joint. The battens hold the planks together. Sometimes a long diagonal slat or two are also implemented to prevent the door from skewing. In some doors, the battens are replaced with iron bars. 

Paneled door

Panel doors, also called stile and rail doors, are built with frame and panel construction: They consist of a frame made up of stiles, a top rail, a bottom rail, and sometimes an intermediate rail. Into this framework a plywood panel is fitted. This panel may fit into a groove or a rebate. This door is used as external door.

Glazed door 

They are similar to Panels door except Panels are in glass. They are normally made up of timber and used as internal door.

Flush door

These types include many modern doors, including most interior doors. They are joint-less; the rails and frame are hidden. Normally the frame is made up of  timber. They are used as internal doors.

Sliding door

A sliding door is a type of door which opens horizontally by sliding. Panels are fixed with wheels on their top & bottom. The wheels run over the iron or hardwood. The panel slide across saving space. They are common in aluminum and steel.

Revolving door

The revolving door is the movement of personnel between roles as legislators and regulators. It helps to maintain thermal condition inside the room. It is found in the entrance of public buildings. 

Collapsible door

They are fabricated from mild steel. They have scissor joints and collapse on sides and save space.

Roller shutters

Roller shutters are closures where the door leaf rolls up above the doorway. Panel coils up on the top. They are used mostly in shops and stores.

Swing door

It can be opened on either side (double/top hinged). It is found in restaurants and public spaces.

Solid core door

It is laminated door section. Fame is made of timber. Hardwood or pressed wood may be used for core of the frame.

Nuwood door

Nuwood is the artificial wood. It gives fine finishing. The wood is cut to desired shape & size. Nuwood can be used to form solid core.

 Retaining Wall and Water Proofing

Retaining Wall:

A retaining wall is a structure designed and constructed to resist the lateral pressure of soil. Retaining walls are built in order to hold back ground. Lateral earth pressures are zero at the top of the wall & a maximum value at the lowest depth. Earth pressures will push the wall forward or overturn it if not properly addressed. The basement wall is thus one form of retaining wall. Most often used to refer to a cantilever retaining wall which is a freestanding structure without lateral support at its top.

Function of retaining wall

• Strength stability & durability
• Resistance to overturn
• Resistance to horizontal slide
• Resistance to overstress in the materials of construction
• Resistance to overstress in the soil on which the wall rest

Design Consideration:

Retaining wall must be ensure that;

1. Overturning does not occur
2. Sliding does not occur
3. The soil beneath the wall is not overloaded
4. The materials in the wall are not overstressed

Forces acting on Retaining walls

The effect of 2 forms of earth pressure need to be considered during the process of designing the retaining wall that is:

1. Active Earth Pressure

     “ It is the pressure that at all times are tending to move or overturn the retaining wall”

2. Passive Earth Pressure

     “It is reactionary pressures that will react in the form of a resistance to movement of the wall"

Angle of repose

It is the natural slope taken up by any soil; It is given in terms of the angle to the horizontal base line. It varies from 45-0̊ for wet soil but for most soil this angle of repose is 30̊

Wedge of soil

This is the soil resting on the upper plane of the angle of repose

Surcharge

This is the additional mass of soil above the top surface of wall

Factors affecting strength, stability & durability 

• Nature and type of soil
• Height of water table
• Sub-soil water movements
• Types of wall
• Materials used in the wall

Types of retaining walls

1. Gravity or mass retaining wall
2. Cantilever or L-shaped retaining wall
3. Sheet piling retaining wall
4. Anchored retaining wall
   
   
   

1. Gravity or mass retaining wall

Gravity walls depend on the weight of their mass (stone, concrete or other heavy material) to resist pressures from behind. With of the base is usually H/4 to H/2 ,where H is the height of wall. For efficiency the wall is sloped in front face. Reinforced to avoid cracking. Height is usually limited to 1.8 to 2 m.

2. Cantilever or L-shaped retaining wall

Cantilevered retaining walls are made from an internal stem of steel-reinforced. These wall have much thinner stem and utilize the weight of the backfill soil to provide most  of the resistance to sliding and overturning, less expensive than mass gravity walls, most common type of earth retaining structure.

3. Sheet piling retaining wall

Retaining properties and water proofing of basements

• Damp Proofing Course (DPC) for basement
• Provided on outside surface of wall and underside of floor of basement
• DPC must withstand the water pressure from underside
• Basement must have sufficient dimension
• Base concrete (PCC) of sufficient thickness to be provided with minimum projection of 15cm beyond outer wall as a protective before DPC
• RCC wall and slab be provided after DPC course
• Asphalt layer is best DPC in basement and it should be continuous
• There must be proper lapping of DPC in joints and cracks
  
  
  

Methods of water proofing

1. Membrane water proofing -rater repelling substance like bituminous felt,  asphalt, silicon etc.

2. Integral waterproofing -adding certain waterproofing compounds into the concrete mix.

3. Surface treatment -Filling up the pores of the surface subjected to dampness-paint, cement slurry etc.

4. Pressure grouting 

5. Cavity of construction

Foundation/Footing and Its Types (Deep)

B) Deep Foundation

 This is preferred where the soil strata at the surface are not very good. The foundation is driven deep into the ground till it reaches a hard strata or compacted soil. Deep foundation can be classified as;

1. Pile foundation 

 Piles are generally used in buildings. Piles are driven into the ground to strengthen the strength of the soil below. 

According to their use they can be classified as,

•  Bearing pile
•  Friction pile
•  Sheet pile
•  Anchor pile
•  Compaction pile
•  Fender pile
•  Batter pile

According to the material used, piles are classified as;

a. Timber piles

b. Concrete piles i. Precast        ii. Cast- in-situ

c. Steel piles

d. Composite piles

2. Well foundation

This foundation is mostly used in black cotton soil which is good for agriculture & bad for structure. This type of soil has high shrinkage value due to change in moisture content and volume varies as 20-30% of original volume. It develops very wide & deep cracks due to excessive shrinkage and is problematic for foundation.

Precaution for foundation in black cotton soil 

•  Foundation depth be enough below from cracks to hard strata
• Prevent foundation from direct contact with black cotton soil
• If thickness of black cotton soil is high,foundation is to be laid on piles
• Raft foundation is the choice in this condition
• Tie-beam in plinth is important

Bearing capacity of soil

It is the ability of soil to support the load coming over it. Bearing capacity of soil depends upon the types of soil.

Methods of improving bearing capacity of the soil

1. Compacting the soil
2. Increasing depth of the foundation
3. Drainage of soil
4. Grouting 
5. Chemical treatment
6. Driving sand piles

Some Common Problem with existing foundation

1. Causes of foundation settlement
2. Consolidation of soil particles
3. Reduction of moisture content
4. General earth movement

Effects of unequal settlement

• Distortion of structure fabrics
• Failure of structure

Prevention of undue unequal settlement

• Proper foundation design
• Proper soil investigation

Causes of foundation failure

• Unequal settlement of sub-soil
• Unequal load distribution
• Horizontal movement of soil adjoining structure
• Lateral pressure tending overturn
• Shrinkage due to withdrawal of moisture from soil
• Atmospheric action
• Lateral escape of soil below foundation
• Nearby building construction
• Trees etc.

Foundation/Footing and Its Types (Shallow)

A building is divided into two parts;

i.   Sub-structure (portion below the Plinth level)
ii. Super-structure (portion above the Plinth level)

 Foundation is the lowest part of the structure below plinth level, which provides base for super structure. It does not take up the load of the structure by itself, it only transfers superimposed load to the soil below.

Objective of foundation

•  To provide a leveled base for the superstructure
•  To transmit all superimposed loads of the structure to the soil
•  To increase stability; prevent tilting or overturning of the structure
•  To prevent unequal settlement 

Types of Foundation 

A) Shallow foundation             B) Deep foundation

A) Shallow Foundation (Wide foundation)

 It is placed immediately beneath the lowest part of the super structure. It is spread more horizontal than vertical. The depth is less than or equal to its width. It transfers the loads to subsoil at a shallow depth, close to the ground level.

Types:
1. Spread Footing: 

The base is made wider than the top so as to distribute the load from the superstructure over a large area.

a) Wall (Strip) Footing

 It is generally used for ordinary building with load bearing walls. The successive increment in the width is achieved by providing 5 cm (1/2 brick) offset at both sides.

b) Reinforced Concrete Footing

 In case of heavy loading, R.C.C. footing proves to be economical over brick footing.

c) Inverted Arch Footing

 It is used where the bearing capacity of the soil is very poor and load of the structure is concentrated over the columns.

d) Column Footing

 It is also known as independent/ isolated footing. It may be constructed using bricks, R.C.C. or stones.

2. Grillage Foundation 

 It is used where the load of the structure is excessive and the bearing capacity of the soil is poor. It is recommended where deep foundation is not possible. Steel and timber grillage foundation are generally used.

3. Combined Footings

 In this footing two or more columns are supported by a single base. They can be Rectangular or Trapezoidal in shape.

4. Raft or Mat Foundation

 Generally this type of foundation is used where the load of the structure is excessive and the bearing capacity of the soil is poor or where basement space is desired and pile is very expensive.