LOW COST HOUSING

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Low Cost Housing is a new concept which deals with effective budgeting and following of techniques which help in reducing the cost construction through the use of locally available materials along with improved skills and technology without sacrificing the strength, performance and life of the structure. There is huge misconception that low cost housing is suitable for only sub standard works and they are constructed by utilizing cheap building materials of low quality. The fact is that Low cost housing is done by proper management of resources. Economy is also achieved by postponing finishing works or implementing them in phases.

Building Cost
The building construction cost can be divided into two parts namely:
Building material cost : 65 to 70 %
Labour cost : 65 to 70 %

Now in low cost housing, building material cost is less because we make use of the locally available materials and also the labour cost can be reduced by properly making the time schedule of our work. Cost of reduction is achieved by selection of more efficient material or by an improved design.

Areas from where cost can be reduced are:-
1) Reduce plinth area by using thinner wall concept.Ex.15 cms thick solid concrete block wall.

2) Use locally available material in an innovative form like soil cement blocks in place of burnt brick.

3) Use energy efficiency materials which consumes less energy like concrete block in place of burnt brick.

4) Use environmentally friendly materials which are substitute for conventional building components like use R.C.C. Door and window frames in place of wooden frames.

5) Pre plan every component of a house and rationalize the design procedure for reducing the size of the component in the building.

6) By planning each and every component of a house the wastage of materials due to demolition of the unplanned component of the house can be avoided.

7) Each component of the house shall be checked whether if it’s necessary, if it is not necessary, then that component should not be used.

Cost reduction through adhoc methods
Foundation

Normally the foundation cost comes to about 10 to 15% of the total building and usually foundation depth of 3 to 4 ft. is adopted for single or double store building and also the concrete bed of 6″(15 Cms.) is used for the foundation which could be avoided.

It is recommended to adopt a foundation depth of 2 ft.(0.6m) for normal soil like gravely soil, red soils etc., and use the uncoursed rubble masonry with the bond stones and good packing. Similarly the foundation width is rationalized to 2 ft.(0.6m).To avoid cracks formation in foundation the masonry shall be thoroughly packed with cement mortar of 1:8 boulders and bond stones at regular intervals.

It is further suggested adopt arch foundation in ordinary soil for effecting reduction in construction cost up to 40%.This kind of foundation will help in bridging the loose pockets of soil which occurs along the foundation.

In the case black cotton and other soft soils it is recommend to use under ream pile foundation which saves about 20 to 25% in cost over the conventional method of construction.

Plinth
It is suggested to adopt 1 ft. height above ground level for the plinth and may be constructed with a cement mortar of 1:6. The plinth slab of 4 to 6″ which is normally adopted can be avoided and in its place brick on edge can be used for reducing the cost. By adopting this procedure the cost of plinth foundation can be reduced by about 35 to 50%.It is necessary to take precaution of providing impervious blanket like concrete slabs or stone slabs all round the building for enabling to reduce erosion of soil and thereby avoiding exposure of foundation surface and crack formation.

Walling
Wall thickness of 6 to 9″ is recommended for adoption in the construction of walls all-round the building and 41/2”for inside walls. It is suggested to use burnt bricks which are immersed in water for 24 hours and then shall be used for the walls

Rat – trap bond wall

It is a cavity wall construction with added advantage of thermal comfort and reduction in the quantity of bricks required for masonry work. By adopting this method of bonding of brick masonry compared to traditional English or Flemish bond masonry, it is possible to reduce in the material cost of bricks by 25% and about 10to 15% in the masonry cost. By adopting rat-trap bond method one can create aesthetically pleasing wall surface and plastering can be avoided.

Concrete block walling

In view of high energy consumption by burnt brick it is suggested to use concrete block (block hollow and solid) which consumes about only 1/3 of the energy of the burnt bricks in its production. By using concrete block masonry the wall thickness can be reduced from 20 cms to 15 Cms. Concrete block masonry saves mortar consumption, speedy construction of wall resulting in higher output of labour, plastering can be avoided thereby an overall saving of 10 to 25% can be achieved.

Soil cement block technology

It is an alternative method of construction of walls using soil cement blocks in place of burnt bricks masonry. It is an energy efficient method of construction where soil mixed with 5% and above cement and pressed in hand operated machine and cured well and then used in the masonry. This masonry doesn’t require plastering on both sides of the wall. The overall economy that could be achieved with the soil cement technology is about 15 to 20% compared to conventional method of construction.

Doors and windows

It is suggested not to use wood for doors and windows and in its place concrete or steel section frames shall be used for achieving saving in cost up to 30 to 40%.Similiarly for shutters commercially available block boards, fibre or wooden practical boards etc., shall be used for reducing the cost by about 25%.By adopting brick jelly work and precast components effective ventilation could be provided to the building and also the construction cost could be saved up to 50% over the window components.

Lintals and Chajjas

The traditional R.C.C. lintels which are costly can be replaced by brick arches for small spans and save construction cost up to 30 to 40% over the traditional method of construction. By adopting arches of different shapes a good architectural pleasing appearance can be given to the external wall surfaces of the brick masonry.

Roofing
Normally 5″(12.5 cms) thick R.C.C. slabs is used for roofing of residential buildings. By adopting rationally designed insitu construction practices like filler slab and precast elements the construction cost of roofing can be reduced by about 20 to 25%.

Filler slabs

They are normal RCC slabs where bottom half (tension) concrete portions are replaced by filler materials such as bricks, tiles, cellular concrete blocks, etc.These filler materials are so placed as not to compromise structural strength, result in replacing unwanted and nonfunctional tension concrete, thus resulting in economy. These are safe, sound and provide aesthetically pleasing pattern ceilings and also need no plaster.

For more on filler materials check Filler Materials Used in Concrete

Jack arch roof/floor
They are easy to construct, save on cement and steel, are more appropriate in hot climates. These can be constructed using compressed earth blocks also as alternative to bricks for further economy.

Ferrocement channel/shell unit

Provide an economic solution to RCC slab by providing 30 to 40% cost reduction on floor/roof unit over RCC slabs without compromising the strength. These being precast, construction is speedy, economical due to avoidance of shuttering and facilitate quality control.

Finishing Work

The cost of finishing items like sanitary, electricity, painting etc., varies depending upon the type and quality of products used in the building and its cost reduction is left to the individual choice and liking.

Conclusion

The above list of suggestion for reducing construction cost is of general nature and it varies depending upon the nature of the building to be constructed, budget of the owner, geographical location where the house is to be constructed, availability of the building material, good construction management practices etc. However it is necessary that good planning and design methods shall be adopted by utilizing the services of an experienced engineer or an architect for supervising the work, thereby achieving overall cost effectiveness to the extent of 25% in actual practice.

Floating Column in Buildings | How it Works | Hanging Columns

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Floating Column or Hanging Columns

The floating column is a vertical member which rest on a beam but doesn’t transfer the load directly to the foundation. The floating column acts as a point load on the beam and this beam transfers the load to the columns below it. The column may start off on the first or second or any other intermediate floor while resting on a beam. Usually columns rest on the foundation to transfer load from slabs and beams. But the floating column rests on the beam.

Hanging or Floating Column Arrangement

This means that the beam which supports the column acts as a foundation. That beam is called as a transfer beam. This is widely used in high storied buildings for both commercial and residential purpose. This helps to alter the plan of the top floors to our convenience. The transfer beam which supports the floating column, transfers the loads up to foundation. Hence this has to be designed with more reinforcement.

Floating Column in Buildings

Now a days multi-storey buildings constructed for the purpose of residential, commercial, industrial etc., with an open ground storey has become a common feature. For the sake of parking, the ground storey is kept free without any constructions, except for the columns which transfer the building weight to the ground. For a hotel or commercial building, where the lower floors contain banquet halls, conference rooms, lobbies, show rooms or parking areas, large interrupted space is required for the movement of people or vehicles. The columns which are closely spaced in the upper floors are not advisable in the lower floors. So to avoid this problem, floating column concept has come into existence.

floating column in a building

In urban areas, multi storey buildings are constructed by providing floating columns at the ground floor for the various purposes which are stated above. These floating column buildings are considered safe under gravity loads and hence are designed only for those loads. But these buildings are not designed for earthquake loads and therefore, these buildings may be unsafe in seismic prone areas. When the floating columns are employed in buildings in seismic prone areas, the entire earthquake of the system is shared by the column or the shear walls without considering any contribution from the floating columns.

Floating column – Palestra Building in London

Floating Column & Earthquake

Though floating columns have to be discouraged, there are many projects in which they are adopted, especially above the ground floor, where transfer girders are employed, so that more open space is available in the Ground Floor. In the earthquake zones, the transfer girders which are employed have to be designed and detailed properly with care. If there are no lateral loads, the design and detailing is not difficult.

construction of floating column

Concept of floating column mainly comprises of disrupting flow of transfer of EQ force.

·         Floating columns are to be designed as a normal compression member.

·         But while designing transfer beam, it is designed as beam carrying all that load of column as a single point load.

·         But is to be kept in mind that EQ force developed must be brought down along the shortest path i.e. load is distributed among two intermediate column supporting that beam.

Floating column is supported by high shear capacity beams/deep beams. At some places we can’t avoid floating columns. Hence, it is wise to revise code provisions for deep beams.

LAYING INSTRUCTIONS FOR TILES

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LAYING INSTRUCTIONS FOR FLOOR TILES

·         Prepare base mortar with cement and sand in the ratio 1:4.

·         Set the levels for floor (i.e. dead level or slope as specified by the Architect / Contractor).

·         Prepare cement slurry i.e. mixture of cement and water to form a thick paste and spread it on the leveled base mortar.

·         Wet the back side of the tile with water. Complete immersion of water is not required.

·         If tiles are square or rectangular in shape, set the right angles for the area and place the first tile along the right angle lines and place it on base mortar. Tap gently only with a rubber or wooden mallet to obtain perfect levels.

·         Clean the surface of the tile with clean water immediately after laying with wet sponge, Ensure the base mortar cement which squeezes through the joints does not settle on the tile. Also ensure that the water used is not hard to brackish.

·         Do not use the area laid for at least 24 hours.

·         Fill in the joints with pointing material which is a mixture of white cement and desired color pigment. For higher quality of finishes, You could use, if required, a polymer based cementitous tilling joint filler like Roffe rainbow. To get the desired color/shade, mix the same with water to form a smooth paste which should be applied to the joints, preferably with the use of rubber squeeze or rubber sheet. Do not apply the pointing material all over the surface.

·         Allow pointing material to set for 15 minutes and then clean the surface of the tile with a clean wet sponge, removing the excess pigment on the tile surface.

·         Wash the surface with soap water or mild detergent to obtain a clean surface and wipe i.t

LAYING INSTRUCTIONS FOR WALL TILES

·         Plaster the surface to be tiled with mortar (cement and sand in the ratio 1:3).

·         Prepare cement mortar i.e. mixture of cement sand and water to form a thick paste and spread it on the back side of the tile after wetting the tile with sponge.

·         Wet the back side of the tile with water. Complete immersion of water is not required.

·         If tiles are square or rectangular in shape, set the right angles for the area and place the first tile along the right angle lines and place it on base mortar. Tap gently only with a rubber or wooden mallet to obtain perfect levels.

·         Clean the surface of the tile with clean water immediately after laying with wet sponge, Ensure the base mortar cement which squeezes through the joints does not settle on the tile. Also ensure that the water used is not hard to brackish.

·         Do not use the area laid for at least 24 hours.

·         Fill in the joints with pointing material which is a mixture of white cement and desired color pigment. For higher quality of finishes, You could use, if required, a polymer based cementitous tilling joint filler like Roffe rainbow. To get the desired color/shade, mix the same with water to form a smooth paste which should be applied to the joints, preferably with the use of rubber squeeze or rubber sheet. Do not apply the pointing material all over the surface.

·         Allow pointing material to set for 15 minutes and then clean the surface of the tile with a clean wet sponge, removing the excess pigment on the tile surface.

·         Wash the surface with soap water or mild detergent to obtain a clean surface and wipe it.

DESIRED SITE CONDITIONS FOR LAYING OF TILES

The following works are to be completed prior to commencing laying of Ultra Tiles.

·         Final painting of ceiling in rooms.

·         Two coats of wall painting in all rooms (the final painting should be done only after laying of floor tiles).

·         Wiring and fixing of all electrical components.

·         Plumbing work.

·         Fixing of grills for windows.

·         Fixing and polishing of windows / window frames / door frames and doors.

·         Bathrooms floor and walls tiles should be laid after all the work in the bathroom are completed.

·         Fixing of wall and platform slabs.

If Mosaic/Marble/any other natural stone which needs machining and polishing is being used in any other part of the floor, it is necessary that this work be completed before commencing the laying of Tiles.

COMPARISON BETWEEN CPCC, FBEC & CRSD

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Before doing the comparison study lets know what these terms mean.
CPCC –Cement-Polymer Composite Coated Rebars
FBEC – Fusion Bonded Epoxy Coated Rebars
CRSD – Corrosion Resistant Steel Deformed Rebars

1.0   Corrosion Control of Reinforcement bars (Rebars)

40% of failure of structures is on account of corrosion of embedded steel reinforcement in concrete. Therefore corrosion control of steel reiorcement is a subject of paramount importance.First and foremost for corrosion control is the good quality of concrete through good construction practices.

2.0 Cement-Polymer Composite Coated Rebars (CPCC)
System at a glance

Products involved in CPCC normally are:
• De-rusting Solution
• Alkaline Powder
• Phosphating Jelly
• Inhibitor Solution
• Sealing Solution

S No	Parameter	Requirement
1.	Pre-treatment (Surface reparation)	Sand blasting to the near white metal
2.	Primer Coat	To be given within 4 hours of sand blasting.
3.	Sealer Coat	Within 30 minutes of primer coat, this should be given. Thickness 150 microns plus minus 25 microns.
4.	Air curing	Six hours before use in the work.
5.	Continuity of coating	No defects such as cracking, bulging, peeling, no rust mark. Inspect visually.
6.	Adhesion of coating – test	Coated bars are bent at 120 o around a mandrel. NO peeling or cracking should be observed on outer radius.
7.	Stacking	Stack bars on buffer material.
8.	Cutting , bending, welding	Coat bars can be cut and bent. Cut ends and weld positions should be treated with same formulation.

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This system has been developed mainly as a factory / shop process.
• The approach behind development of this system is that the base metal of rebars, contains ? electrons which get readily released in corrosive environment leading to oxidation of iron and thereby formation of Ferrous Oxide (II) (rust) as principal deterrent.

• In order to prevent this oxidation a surface coating capable of interacting/nullifying the released electrons is provided.

• Further pre-stressing and reinforcing steel, in concrete during service life, are exposed to an alkaline environment and this necessitates introductions of a top coat which should be compatible to primer and alkaline environment.

3.0 Fusion Bonded Epoxy Coated Rebars (FBEC)
System at a glance

No.	Parameter	Requirement
1.	Pre-treatment (Surface reparation)	1. Bars are first cleaned from surface contamination such as oil, grease etc. by chemical process before shot blasting. 2. The reinforcement bars are cleaned by shot blasting or grit blasting to white or near white stage. 3. The blast cleaned bars are then heated through induction heaters at preset temperature level around 230°C.
2.	Coating	Hot bars are then fed to the coating booth, where the epoxy powder is sprayed electrostatically.
3.	Curing and Cooling	Coated bars are then cured and forced cooled by water spraying to enable handling and testing.
4.	Continuity of coating	On line and off line holiday checks, thickness checks are carried out. The adhesion of the coated bars is also tested frequently by bending of the bar.
5.	Testing of Performance of rebar	Various other tests are performed in laboratory like chemical resistance, short spray, resistance in continuance boiling water, abrasion resistance and impact resistance etc. These are conducted on every batch of production.
6.	Handling & Stacking	Fusion Bonded Epoxy Coated Bars require padded contacts during transportation, stacking, handling and till the concreting is done.
7.	Cutting, bending & welding	The cut ends, welded spots and handling damages are required to be repaired with special liquid epoxy compatible with the coating material as per specification of the coating agency.

• Fusion bonded epoxy is basically 100% solid finely ground fused powder particles, which when heated; melt to form a continuous adherent film.

• There is no passivating primer film provided in case of FBEC rebars.

• This coating introduces a medium of weakness in the path of an intimate bond between rebar and alkaline concrete.

• Extensive investigation carried out on 40 bridges in Florida Key in USA has revealed that disbandment can occur easily in the FBEC rebars which lacked passivation layer of Ferrous oxide (II) and is a precursor to corrosion.

• Higher co-efficient of Thermal Expansion of fusion bonded epoxies impose large thermal stresses in epoxy coating leading to its early failure.

Epoxy coats the rebar in the following manner:
Melts
Flows
Gels
Cures
Cools
Adheres as coating

4.0 Corrosion Resistant Steel Deformed Rebars (CRSD)
• Mechanism of resistance to corrosion begins with the formation of initial layer of protective oxide or rust. (Hypo oxides). Unlike common rust on normal rebars, the CRSD rust is passive, tenacious and self-renewing.

• The protective oxide is fine textured, tightly adherent and a barrier to moisture, oxygen, carbon dioxide, Sulphur dioxide and chloride effectively preventing further corrosion.

• Scale on normal bars of steel is coarse textured flaky oxide that does not prevent moisture or oxygen from reaching the underlying bars and continuing the corrosion.

• As corrosion resistance is in the chemistry of the grade, if the passive oxide layer gets removed somehow, a new passive layer is formed immediately.

CRSD – Mechanical Properties
Properties	IS:1786 Fe500D	CRSD
Yield Stress, YS (min, N/mm2)	500	500
% Elongation	16	16
Ultimate Tensile Strength, UTS (min, N/mm2)	565	580

5.0       Comparison (CPCC – FBEC – CRSD)

Parameters	CPCC	FBEC	CRSD
Thickness of Coating	175 mm – 300 mm	300 mm – 675 mm	No coating required
Type of Protection to rebar	Extrinsic	Extrinsic	Intrinsic
Pre-treatment	Pretreatment is required before coating	Pretreatment is required before coating	No pre-treatment required
Treatment to surface	Before coating the surface made little rough when some damage is introduced.	Before coating the surface made little rough when some damage is introduced.	The surface of the finished good is not disturbed or damaged at all.
Temperature treatment	The whole process is done at room temperature.	230°C – 400°C	No treatment required
Special Bending requirement	Modified mandrel diameter is specified by Indian Standard	Modified mandrel diameter is specified by Indian Standard	Same as other TMT rebars of Fe 500D grade
Defects introduced	Holiday Effect	Holliday Effect	Nil