Constructing a House
This project is about constructing a new home, as the title states.
The Problem
The problems are the whole project needs to be split into a series of activities (some need to be carried out simultaneously), each activity requires a certain amount of time to complete and the number of workers required to complete the activity on time in order to complete the whole project on time without any delays.
The project can only be completed on time if:
* There are sufficient resources
* There are sufficient number of workers
* The workers are multi skilled
The project is split into 41 activities.
Activity A - Purchase land
* No. of workers required - 1
* Duration - 2 days
* Precedence - N/A
This is because 1 person is required to discuss the sale of a suitable plot of land. It also requires 2 days to complete the sale of the plot of land; 1 day to discuss the choices of plots of land and another to agree on a sale and process the order. The processing takes a few hours by sending the order from the sales office to the sales headquarters, where they have other orders to process, and then sending the information back to the sales office, confirming that the land is sold. This activity must be carried out with activity B (below).
Activity B - Design house
* No. of workers required - 4
* Duration - 4 days
* Precedence - N/A
This is because 4 people are required to each plan and draw their own designs of the house. Then they decide which design is the best out of all of the designs. This takes place over 3 days. The final design is drawn carefully on the final day of the activity. This activity must be carried out with activity A (above).
Activity C - Seek planning permission
* No. of workers required - 1
* Duration - 3 days
* Precedence - A and B
This is because 1 person is required to present the final design to the council at the nearest town hall to the site. This takes place over 3 days as the councillors need to discuss the factors which make the construction of the design legal. Then the representative informs the person who presented the design whether the construction of the house is allowed to go head or not. By law, all building designs must be submitted to the council to determine whether the construction of each of the designs is legal or not. If the building is illegally constructed, the owner of the property is forced to demolish it within 12 months, or else face fines or court charges. This activity is carried out after A and B has been carried out.
Activity D - Excavate foundations
* No. of workers required - 4
* Duration - 2 days
* Precedence - C
This is because 4 people are required to carry out the activity. They have to dig up the ground in order to lay the foundations afterwards. This takes place over 2 days. This activity is carried out simultaneously with activity E.
Activity E - Excavate drains
* No. of workers required - 3
* Duration - 2 days
* Precedence - C
This is because 3 people are required to carry out the activity. They find the nearest drain and excavate it in order to lay the drains and connect them together so rainwater can flow to the sewage plant. This takes place over 2 days. This activity is carried out simultaneously with activity D.
Activity F - Lay drains
* No. of workers required - 2
* Duration - 2 days
* Precedence - E
This is because 2 people are required to carry out the activity. They lay the new drain on the site of the house and connect it with the main drain. They also decide the path of the drain and lay the drains. Also gas pipes are laid as well. This takes place over 2 days. This activity is carried out after E has been carried out.
Activity G - Backfill drains
* No. of workers required - 2
* Duration - 1 day
* Precedence - F
This is because some parts of the drain must be exposed on the ground so rainwater can flow into the drain. The exposed parts are covered with a strong, durable metal grid. This involves covering some parts of the drain with earth or tarmac and exposing them at a certain length away from other exposed parts. This activity is carried out after F has been carried out.
Activity H - Lay foundations
* No. of workers required - 3
* Duration - 3 days
* Precedence - D
When the hole is deep enough, the foundation, consisting of concrete and chipped stones, are poured into the ground, levelled out and left dry for one day. The laying process takes two days. This activity is carried out after D has been carried out.
Activity I - Brickwork to ground floor level
* No. of workers required - 4
* Duration - 3 days
* Precedence - H
When the foundation is dry brick work can start. This goes on until the brick level reaches the top of ground floor. The brick work cannot go on up to the roof level because later on the builders will face difficulty of constructing the first floor and carrying activities associated with the first floor. This activity is carried out after H has been carried out.
Activity J - Concrete Slab
* No. of workers required - 3
* Duration - 3 days
* Precedence - G and I
This involves pouring concrete over the foundation and levelling it so it is smooth. This is because when the carpet is laid, the residents of the house feel comfortable. The concrete will dry faster since it is exposed to the atmosphere, rather than confined inside the building, causing it to dry a lot more slowly. This activity is carried out after activity G and activity I has been carried out.
Activity K - Construct wooden frame
* No. of workers required - 5
* Duration - 4 days
* Precedence - J
This activity is concerned with constructing the first floor, door, garage and outer wall frames. This is because windows, doors and garage door can be fitted easily. Roof carpentry will be easily carried out since parts of the roof frame can fit onto the outer wall frame to relieve the stress and tension of the building. This means that the tension travels down from the roof through the walls and outer wall frame to the ground. This prevents the ...
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* No. of workers required - 5
* Duration - 4 days
* Precedence - J
This activity is concerned with constructing the first floor, door, garage and outer wall frames. This is because windows, doors and garage door can be fitted easily. Roof carpentry will be easily carried out since parts of the roof frame can fit onto the outer wall frame to relieve the stress and tension of the building. This means that the tension travels down from the roof through the walls and outer wall frame to the ground. This prevents the structure from collapsing. This activity is carried out after J has been carried out.
Activity L - Brickwork to roof level
* No. of workers required - 4
* Duration - 4 days
* Precedence - K
This is because bricks have to be laid to roof level in order for the internal structures and decorations to be carried out. This activity is carried out after K has been carried out.
Activity M - Roof carpentry
* No. of workers required - 4
* Duration - 4 days
* Precedence - L
This activity is significant because the roof frame supports the roof tiles without them collapsing into the first floor of the house. This activity is carried simultaneously with N.
Activity N - Windows and outside doors
* No. of workers required - 2
* Duration - 2 days
* Precedence - L
Windows and external doors are fitted onto the house after activities A to L are completed. This activity is significant because after this activity is finished, glazing is fitted. If the windows and external doors are fitted when the glazing is fitted, some parts of the glazing has to be cut away to allow room for the windows and external doors to fit into the required space. This would cause inconvenience and the glazing may have to be refitted, causing costs to increase. This activity is carried simultaneously with M.
Activity O - Glazing
* No. of workers required - 3
* Duration - 2 days
* Precedence - N
Glazing decreases the amount of heat lost by conduction and convection through walls, roof, windows and doors. This adds value to the property as consumers want to live in comfortable homes. The energy is saved, decreasing the rate of global warming. This activity is carried out after N has been carried out.
Activity P - Tile roof
* No. of workers required - 3
* Duration - 5 days
* Precedence - M
This activity involves fitting tiles on the roof over the roof frame to increase the durability of the roof, making it last for years. This prevents water from leaking into the house, making it damp. The dampness causes the wooden parts of the house to rot. If this happens, the wooden parts will have to be replaced as the rotting weakens the structure of the house. This activity is carried out after M has been carried out.
Activity Q - Fit partitions
* No. of workers required - 5
* Duration - 5 days
* Precedence - P
This means that the inner walls are fitted inside the house according to the plans. Metal frames are constructed and then fitted to make the wall robust. Then the wooden frames are fitted so the wall takes into shape. The stairs to the first floor is constructed as well. Any wires to the plug sockets are concealed. This activity is carried out after P has been carried out.
Activity R - Fit rainwater pipes
* No. of workers required - 2
* Duration - 1 day
* Precedence - P
Pipes, which carry rainwater to the drains, are fitted on the sloping end of the tiled roof because the rainwater will flow down the roof due to gravitational pull and then it flows into the pipes, instead of homeowner's head. This activity is carried out after P has been carried out.
Activity S - Fit internal doors
* No. of workers required - 1
* Duration - 2 days
* Precedence - R
Doors are fitted inside the house. First the hinges are fitted then the side of the door is screwed to the hinge. This process is repeated until all of the doors are fitted inside the house. This activity is carried out after R has been carried out.
Activity T - Fit out plumbing
* No. of workers required - 2
* Duration - 2 days
* Precedence - Q
The pipes are fitted inside the house so they can be linked to the drain so waste can flow away from the house. This activity is carried out after Q has been carried out.
Activity U - Plumbing pipe work
* No. of workers required - 1
* Duration - 2 days
* Precedence - T
This activity involves connecting all of the pipes inside the house to the drain. This activity is carried out after T has been carried out.
Activity V - Decorate interior
* No. of workers required - 3
* Duration - 7 days
* Precedence - S, U and X
This activity involves applying plaster to the walls that divide up the space of the house. This activity is carried out after activities S, U and X has been carried out.
Activity W - Fit electrical conduit
* No. of workers required - 1
* Duration - 1 day
* Precedence - Q
This involves fitting electrical wires inside the walls so they can be wired to the plug sockets. This activity is carried out after Q has been carried out.
Activity X - Electrical wiring
* No. of workers required - 1
* Duration - 1 day
* Precedence - W
Basically, one person connects all of the wires to each of the plug sockets. Wiring a plug socket only takes about 5 minutes. This activity is carried out after W has been carried out.
Activity Y - Interior joinery
* No. of workers required - 2
* Duration - 3 days
* Precedence - V
This activity involves constructing banisters, door frames and kitchen surfaces. It takes one day to construct the banisters and fit door frames. It takes two days to construct kitchen surfaces. This activity is carried out after V has been carried out.
Activity Z - Install kitchen sink
* No. of workers required - 1
* Duration - 1 day
* Precedence - Y
Kitchen sink is fitted and connect the pipes, one which supplies water and one which lets waste water flows to the drain, to the kitchen sink. Tests are conducted to make sure the taps work properly, but if they do not corrections are made. This activity is carried out after Y has been carried out.
Activity AA - Install cooker
* No. of workers required - 1
* Duration - 1 day
* Precedence - Y
A cooker is installed in the kitchen and gas pipes are connected to the cooker. Tests are conducted to make sure the taps work properly, but if they do not corrections are made. This activity is carried out after Y has been carried out.
Activity AB - Install boiler
* No. of workers required - 1
* Duration - 2 days
* Precedence - V
A boiler is fitted and the water pipes are connected to the boiler. The boiler provides hot water by heating up the tank. Tests are conducted to make sure the taps work properly, but if they do not corrections are made. This activity is carried out after V has been carried out.
Activity AC - Install sink and bath tub
* No. of workers required - 2
* Duration - 1 day
* Precedence - V
A bath tub and a sink are fitted inside the bathroom and then the water pipes are connected to the bath tub and sink. Tests are conducted to make sure the taps work properly, but if they do not corrections are made. This activity is carried out after V has been carried out.
Activity AD - Tile kitchen floor
* No. of workers required - 2
* Duration - 3 days
* Precedence - Z and AA
This is because if liquids are split on the floor, they will be easy to clean as the liquid will not soak into tiles. This is because the tiles have an impermeable surface. Tiles are laid on the kitchen floor and they are left to dry. The mortar holds the tiles together, which makes it durable for long periods of time. This activity is carried out after activities Z and AA have been carried out.
Activity AE - Lay carpets
* No. of workers required - 4
* Duration - 3 days
* Precedence - AB and AC
Carpets are laid in other rooms inside the house. Each piece is laid in one room and they are separated by metal clips, which hold two pieces of carpet together. The metal clips, which are long as the width of the door, are laid on door entrances inside the house, not at the external doors. This activity is carried out after activities AB and AC have been carried out.
Activity AF - Construct fencing
* No. of workers required - 5
* Duration - 2 days
* Precedence - P
Garden fence is constructed to give privacy to the residents of the house. One section of the fence is constructed at one time and this process is repeated until fence construction has finished. Each part of the fence is constructed by placing wooden poles at regular length intervals and then the fence is placed so both edges cover one part of the pole. Then nails are hammered onto the part of the fence which covers the pole. This activity is carried out after P has been carried out.
Activity AG - Tarmac drive
* No. of workers required - 3
* Duration - 1 day
* Precedence - P
Concrete is laid as this will support the weight of the parked vehicle. Then grey, chipped stones mixed with bitumen are laid and then the roller is used to make the laid tarmac smoother and flatter. The drive consists of a thick concrete layer and tarmac layer at 6 inches thick. If the tarmac is not thick enough, the vehicle will sink leaving tyre prints. This activity is carried out after P has been carried out.
Activity AH - Lay grass
* No. of workers required - 4
* Duration - 3 days
* Precedence - AF
The soil is levelled then the grass is laid in sections. While the grass is being laid, nobody will be allowed to step onto the newly laid grass as it causes the ground to be bumpy. Then the grass is left untouched for the next two days so the roots grow and reaches into the soil. This activity is carried out after AF has been carried out.
Activity AI - Pave path to back garden and to front door
* No. of workers required - 4
* Duration - 1 day
* Precedence - AF
The side path, which leads to the back garden, and the front door path are laid after the grass has been dug according to plans. This activity is carried out after AF has been carried out.
Activity AJ - Fit side gate
* No. of workers required - 1
* Duration - 1 day
* Precedence - AH and AI
The side gate is fitted in a similar way as doors are being fitted but like external doors, the lock and gate hinge, which opens the gate when the hinge is lifted, are fitted. This activity is carried out after activities AH and AI has been carried out.
Activity AK - Install toilets
* No. of workers required - 3
* Duration - 2 days
* Precedence - AB and AC
Toilets are fitted in the toilet and bathroom. This involves constructing each of the toilets and connecting them with large pipes so faeces and other waste can flow to the drain and then to the sewage plant. Each toilet is tested and corrections are made, if necessary. This activity is carried out after activities AB and AC have been carried out.
Activity AL - Tile bathroom walls
* No. of workers required - 2
* Duration - 3 days
* Precedence - AK
Bathroom walls are tiled because if the tile gets wet, water will not soak into the tile so water runs off it. This is due to the fact that the tiles are impermeable. This activity is carried out after AK has been carried out.
Activity AM - Decorate
* No. of workers required - 8
* Duration - 8 days
* Precedence - O AD, AE, AJ and AL
The house is decorated with white paints and decorations, which have a neutral effect on peoples' personalities. This is because this will make the house more saleable as all people have different personalities. If the decoration is biased towards a certain personality, few people will want to buy the home as some will do not like a particular look or part of the decoration. Decorations with neutral effect will leave room for homeowners to decorate the home to suit their lifestyle. This activity is carried out after activities O, AD, AE, AJ and AL have been carried out.
Activity AN - Clean house
* No. of workers required - 6
* Duration - 1 day
* Precedence - AM
Any mess made by the decorating activity or any other activity will be cleared up. This adds value to the property as potential buyers will instantly recognise it as a clean, new home. This also means that the person who plans the project will earn larger profits. This activity is carried out after AM have been carried out.
Activity AO - Put house up for sale
* No. of workers required - 1
* Duration - 3 days
* Precedence - AN
One person is required to put the house up for sale by submitting a sale to an estate agent. Then the submitting process takes a few days because the sales headquarters may have to process other sales. Then the letter is sent to the person's address confirming that the house is successfully put up for sale. This activity is carried out after activity AN have been carried out. After this activity has finished, the whole project is complete.
Sources of information
The information in this write up came from the following sources:
* My witness accounts
* Ground Force
* www.chemical-industry.org.uk
The Aim
The aim of this project is to find the minimum completion time for the house construction project, if there are sufficient resources.
Is the problem related to others?
The project is related to other construction projects, for example:
* School
* Semi-detached house
* Terraced house
* Flat
* Bungalow
* College
* Town hall, etc.
This is because these projects require similar activities, for example excavate foundations, plumbing work, etc. They require the same type of workers and have similar completion time. They also have similar type of problems, which need to be solved in order for the project to be a success.
Solution
The following are on separate sheets of paper:
* Precedence table
* Activity network diagrams
* Forward and backward pass
* Floats of non-critical activities
* Minimum completion time
* Critical activities and paths
* Cascade diagram
* Resources histogram
* Job allocation diagram
* Cascade diagram with ordered activities using CAN (Cascade Activity Number)
* Resource levelling first and second attempts
Which activities could cause delays?
The following activities are likely to over run, causing delays:
* A - Purchase land
* B - Design house
* C - Seek planning permission
* L - Brickwork to roof level
* P - Tile roof
* Y - Interior joinery
* AM - Decorate
Activity A
If no suitable plot of land is found, there would be a delay of up to 14 days. This may be caused by not searching more available plots of land. This would increase the minimum completion time to 82 days maximum, since there are 2 slack days.
Activity B
If the design team goes into a disagreement for any reason or the final design is not completed on time, there would be a delay of 2 days. This might be caused by poor teamwork. This would increase the minimum completion time to 72 days.
Activity C
If the planning permission is refused or delayed by the council responsible, the whole project would be delayed by 4 days. This is because of the designers not considering which structures are legal or not. This would increase the minimum completion time to 74 days.
Activity L
If the mortar doe not dry by the end of the activity deadline, which is the end of forth day, this would delay other activities by 1 day. The minimum completion time would be increased to 71 days.
Activity P
If all of the tiles are not fitted onto the roof on time, the project would be delayed by 1 day, increasing the minimum completion time to 71 days.
Activity Y
If parts of the banisters, door frames and/or kitchen surfaces do not fit properly, delays would be up to 2 days. This means that the whole activity may have to be restarted. This would increase the minimum completion time up to 72 days.
Activity AM
If the decoration activity goes wrong by using the wrong paint, drilling the hole at the wrong place, for example, the project would be delayed by up to 4 days. This would increase the minimum completion time by up to 74 days.
Solutions to combat delays
For activity A, send 4 people to search for a suitable plot of land. This cuts the work load of one person and spreading it to other people. The amount of stress for one person is significantly reduced. More people means the search is a lot faster so that means that the activity can be completed a lot quicker.
For activity B, introduce the designers to each other so they will get to know each other and teamwork will be better. This reduces the likely of designers going into disagreement.
For activity C, inform designers about which structures are legal or not and encourage them to ask each other or the manager questions, if in doubt of the structure suggested.
For activity L, use 6 people to do the brickwork to roof level as the extra people will take the work load off the existing workers. This also speeds up the process.
For activity P, provide 2 extra workers as the tiling process will be speeded up and the work load will be reduced per one worker.
For activities Y and AM, produce simple plans and inform decorators to ask questions to each other or the manager, if in doubt about one or more parts of the decorating plan. Give the decorators plans of the decoration in advance so they will be more likely know what they will be doing when the activity starts, reducing the probability of making mistakes.
Allocating jobs to workers
Planners:
* Activity A
* Activity C
* Activity AO
Designers:
* Activity B
Builders:
* Activity D
* Activity E
* Activity F
* Activity G
* Activity H
* Activity I
* Activity J
* Activity L
* Activity N
* Activity O
* Activity P
* Activity Q
* Activity R
* Activity S
* Activity AF
* Activity AG
* Activity AH
* Activity AI
* Activity AJ
Decorators:
* Activity V
* Activity AD
* Activity AE
* Activity AL
* Activity AM
* Activity AN
Carpenters:
* Activity K
* Activity M
* Activity Y
Plumbers:
* Activity T
* Activity U
* Activity Z
* Activity AC
* Activity AK
Engineers:
* Activity W
* Activity X
* Activity AA
* Activity AB
Findings and Refinement
The findings suggest that the duration of the whole project is too short and an activity for constructing a garage is not included. In the real life, a detached home construction project would have taken about 90 to 180 days, depending on the style and size of the home, to complete and most modern homes have garages, because many homeowners have a second car. They can also use them for storage purposes as well.
Conclusions on assumptions
It is suggested that there are sufficient number of workers and resources. This is because there are enough qualified people who can carry out this project and due to demand, enough resources of certain materials are produced so they can be ordered and arrive to the building site when needed.
The workers, who will be carrying out the project, are not multi-skilled because some workers have certain qualifications to specialise in certain jobs. Anybody who is untrained to carry out any construction or designing work, for example, will cause problems by making mistakes. This causes delays, increasing the minimum completion time and costs.
This means that the manager will have to hire certain number of planners, designers, builders, decorators, carpenters, plumbers and engineers to carry out the project. If this is not the case the starting time for the project may have to be delayed until there is enough planners, designers, builders, decorators, carpenters, plumbers and/or engineers have been drafted in.
Other factors that might affect the project
* If there is evidence of enough demand for housing, the project can commence. Otherwise the project is cancelled if there is low demand for housing.
* If the workers go on strike for any reason. This is because they may have been paid poor wages or treated unfairly.
* If accidents of any form happen during the duration of the project. This will certainly delay the whole project until the injured worker has been taken to the hospital and the mess, caused by the accident, has been cleared up.
* If there are delays of deliveries for any reason. This will cause delays as the activity may not be carried out as vital equipment and/or materials, required for the activity, are not at the building site to be in use.
* If the weather conditions are bad, the project may have to be delayed, because if the rain will get the wooden parts of the house wet, the wood will rot. This will weaken the wood and it has to be replaced immediately as this will cause more problems in the later stages of the project, e.g. structural, etc.
* If the working conditions are unsafe, the whole project will be delayed until the problem has been solved and it has been declared safe to enter the building site.
Improvements
The project can be improved by extending the minimum completion time and adding few activities, such as construct garage. This would attract more buyers and the problems, presented above, would be reduced, as workers will have more time to complete the activities required to complete the project.
Application of model to other projects
The model may be applied to similar construction projects, for example:
* School
* Terraced houses
* Police/fire station
* Hospital
* Restaurants
This is because the projects require the similar activities, number of workers, materials, duration and equipment to complete the whole project. These projects in common require the same type of workers with relevant qualifications.
As with all models, there are limitations. The model might be cannot be applied to construction projects which have a different problem, for example:
* Suspension bridges
* Skyscrapers
* Military bases
These projects require totally different kinds of activities, number of workers materials, duration and equipment in order for any of them to be completed successfully. If problems occur in these projects, the costs can increase dramatically. Careful planning and hiring well qualified people has to be considered if the projects have any chance of being successful in the long term.
Martin Yau
Candidate Number 6079
Centre Number 58231
