Building A 3-Bedroom Flat: A Step-By-Step Guide

Building a house from the ground up is a great solution to the problem of rising house and rental prices. However, not knowing how much construction will cost often discourages people from pursuing this option. The number of blocks required to build a three-bedroom flat depends on the size and complexity of the building. A typical three-bedroom flat will require about 2650 blocks, but if each room has a bathroom, a few extra blocks will be needed. The cost of blocks varies by location, but on average, a block costs N200. Therefore, an individual looking to build a three-bedroom flat should budget around N530,000 for blocks.

Calculating the number of blocks needed for a 3-bedroom flat

The number of blocks needed to build a 3-bedroom flat depends on several factors, including the type of block, size of the building, and area of the walls.

Sandcrete blocks are a popular choice for construction in certain regions, and they come in different types and sizes. The size of the block is an important factor in determining how many blocks are required to complete the building.

To estimate the number of blocks needed, it is essential to have a building plan. This plan will outline the specific dimensions and requirements of the 3-bedroom flat.

For example, let's consider a 3-bedroom flat with the following features:

• One sitting room
• Three bedrooms (all en-suite)
• A visitor's toilet
• A dining area
• A kitchen
• A store
• Sit-out areas

To calculate the number of blocks needed, we need to consider the different phases of construction:

Phase 1: Foundation to DPC (Damp Proof Course)

In this phase, we consider the total length of the walls and the height of the walls at the foundation level. There are no openings, and the entire foundation excavation length is considered.

Let's assume the total length of the walls at the foundation level is 100,256 mm, or 100.256 meters.

The height of the wall from the foundation to the DPC is 900 mm, or 0.9 meters.

Therefore, the total area of the wall is 100.256 meters x 0.9 meters = 90.2304 square meters.

If we assume that 10 blocks are required for 1 square meter of the wall, then we would need 903 blocks for this phase (disregarding wastage and damages).

Phase 2: DPC to Lintel Level

In this phase, we need to consider openings in the building, such as doors and windows. We calculate the total length of the walls, excluding areas without walls like verandahs, and then subtract the area of the openings.

Let's say the total length of the walls is 87,420 mm, or 87.42 meters.

The height of the wall is 2100 mm, or 2.1 meters.

The total area of the wall is 183.582 square meters.

Now, let's calculate the total area of doors and windows.

For doors:

• Door Type 1 (D1): 1 door with dimensions of 2100 mm x 1200 mm
• Door Type 2 (D2): 6 doors with dimensions of 2100 mm x 900 mm
• Door Type 3 (D3): 4 doors with dimensions of 2100 mm x 700 mm

For windows:

• Window Type 1 (W1): 12 windows with dimensions of 1200 mm x 1200 mm
• Window Type 2 (W2): 4 windows with dimensions of 600 mm x 600 mm

Let's calculate the total area of doors and windows:

• Total area of doors = 19.74 square meters
• Total area of windows = 18.72 square meters

Now, we can calculate the net area of the walls:

582 square meters (total wall area) - 19.74 square meters (door area) - 18.72 square meters (window area) = 145.122 square meters

Hence, the total number of blocks required for this phase is 1452 blocks (disregarding wastage and damages).

Phase 3: Lintel Level to Overhead Level

In this phase, we assume that the building will be chained at the lintel level, which means reinforcing the entire level with steel to improve structural integrity and reduce cracking.

We will use the length of the wall without considering openings, so we take the length from the foundation level, which is 100.256 meters.

The height of the wall is 675 mm, or 0.675 meters.

Therefore, the area of the wall is 67.6728 square meters.

Hence, the total number of blocks required for this phase is 677 blocks (disregarding wastage and damages).

Total Number of Blocks Required

To complete the construction of the 3-bedroom flat, we add the number of blocks from each phase:

903 blocks (Phase 1) + 1452 blocks (Phase 2) + 677 blocks (Phase 3) = 3032 blocks

To account for wastage and damages, it is recommended to increase the total number of blocks by 10% to 20%.

So, the total number of blocks needed to build the 3-bedroom flat, including wastage, would be approximately 3638 blocks.

This calculation provides a rough estimate, and the actual number of blocks required may vary depending on the specific building plan and construction methods used.

The cost of blocks and how many are required for a 3-bedroom flat

The number of blocks required to build a three-bedroom flat depends on several factors, including the type of block, the size of the building, and the area of the walls to be built.

Sandcrete blocks are a popular choice for construction, and they come in different types and sizes. The most common types are the 5" and 6" blocks, which are typically used for small projects due to their lower cost. The length of a standard sandcrete block is 18 inches or 450mm or 0.45m.

To estimate the number of blocks needed, you can start by calculating the total external and internal dimensions of the building, also known as the girth. This involves adding up all the external and internal wall lengths.

For a three-bedroom flat, let's assume the following dimensions:

• Total external girth: 39,925mm or 39.9m
• Total internal girth: 23,850mm or 23.85m

So, the total girth (external + internal) = 82,425mm or 82.42m.

Next, we need to determine how many blocks are needed to reach the DPC (Damp Proof Course) level. This is usually 4 "coaches" or levels, but it can be more if the site is swampy.

The formula for calculating the number of blocks per coach is:

Number of blocks per coach = Total Girth / Length of one block

Using the values from our example:

Number of blocks per coach = 82,425mm / 450mm = 183 blocks/coach

For 4 coaches to reach the DPC level:

183 blocks/coach x 4 coaches = 732 blocks

Now, let's determine the total number of blocks needed for the entire three-bedroom flat, considering the different segments of the building:

• From Foundation to DPC: 4 coaches
• From DPC to window level: 4 coaches
• From the bottom of the window to the top of the window: 5 coaches
• From the lintel to the base of the roof: 3 coaches

So, we have a total of 16 coaches.

Total number of blocks for the entire flat = 183 blocks/coach x 16 coaches = 2,928 blocks

Now, we need to deduct blocks for voids, such as doors and windows.

For doors:

• Standard door size: 900mm or 3 feet
• Number of blocks to deduct for a 900mm door = 9 blocks (height) x 2 blocks (width) = 18 blocks

For windows:

• Standard window size: 1,500mm
• Number of blocks to deduct for a 1,500mm window = 6.5 blocks (height) x 3.3 blocks (width) = 22 blocks

Let's assume there are:

• 7 doors, so 7 x 18 blocks = 126 blocks to deduct
• 8 windows of the standard size, so 8 x 22 blocks = 176 blocks to deduct

Total blocks to deduct for voids = 126 blocks (doors) + 176 blocks (windows) = 302 blocks

Final calculation:

Total number of blocks needed for the three-bedroom flat = 2,928 blocks – 302 blocks (voids) = 2,626 blocks

To account for wastage, it is recommended to increase this number by 10-20%. So, for a 10% increase:

2,626 blocks x 1.10 = 2,888 blocks

Therefore, approximately 2,888 sandcrete blocks would be required to construct the walls of a three-bedroom flat, according to this example.

Please note that the cost of blocks can vary depending on the region, supplier, and market conditions. The above example provides a general guide on calculating the number of blocks needed, and the cost would depend on the specific type of block chosen and the prevailing market prices.

The types of blocks used to build a 3-bedroom flat

Building a three-bedroom flat requires a variety of concrete blocks, which are classified into two main types: hollow and solid. The type of block used depends on the specific construction needs and budget. Here is an overview of the types of blocks that can be used to build a three-bedroom flat:

Hollow Concrete Blocks

Hollow concrete blocks are ideal for building large structures like boundary walls. They are lighter due to the holes, which can also be useful for running wiring or piping. Rebar can be inserted into the holes for added stability. There are three grades of hollow concrete blocks: Grade A, with a minimum density of 1,500 kg/m3; Grade B, with a density of less than 1,500 kg/m3; and Grade C, with a density greater than 1,000 kg/m3. Grades A and B are used for load-bearing walls, while Grade C is for non-load-bearing walls. Hollow concrete blocks come in various sizes, such as 100 mm x 200 mm x 400 mm, and different colours, including grey, tan, and dark red.

Solid Concrete Blocks

Fully solid concrete blocks are often used for projects that require stability and durability, such as paving. They are also useful for building walls that protect against the elements, like strong winds. Additionally, they can be used for garden walls, planters, retaining walls, foundations, steps, and firepits. Solid concrete blocks usually have the appearance of large grey bricks. While they tend to be heavier than hollow blocks, they can be more cost-effective.

Aerated Autoclaved Blocks (AAC Blocks)

AAC blocks are lightweight, with excellent sound and temperature insulation properties. They are fire-resistant and can be easily shaped, allowing for the use of nails and screws. These blocks are white to light grey and can be customised for sidewalls, partition walls, steel pillars, and infill panels. They are available in blocks, panels, and specialty shapes like lintel blocks and U-shaped bond beam blocks.

Cellular Lightweight Blocks

Cellular lightweight blocks are made of foam, fly ash, and cement, providing good insulation against sound and temperature. They are fire-resistant, environmentally friendly, and relatively inexpensive. These light grey blocks can be customised for size and used for wall panels, compound walls, and parapet walls. High-density cellular lightweight blocks are suitable for load-bearing or partitioning walls, while medium-density blocks can be used for non-load-bearing brickwork.

Expanded Clay Aggregate Blocks

These blocks are made of lightweight fly ash and cement aggregates, offering fire resistance and waterproofing. They can reduce the overall structural load by up to 50% and provide good sound and temperature insulation. The material can be moulded into various sizes and densities due to being fired in a kiln.

Sandcrete Blocks

Sandcrete blocks are commonly used as load-bearing elements or partition panels in building construction. They come in different types and sizes, and the size of the block is a factor in determining the number of blocks needed to complete a building.

The specific type, size, and quantity of blocks required for a three-bedroom flat will depend on the building plan, dimensions, and local construction norms.

The number of cement bags needed for a 3-bedroom flat

The number of cement bags required to build a three-bedroom flat depends on several factors, including the size of the rooms, the number of rooms, and the thickness of the walls.

A medium-sized three-bedroom flat typically requires approximately 95-100 bags of cement. This estimate is based on a house that consists of a living room and dining room measuring 12x12 feet, three bedrooms with a bathroom, and a kitchen.

However, it's important to note that the number of bags may vary depending on additional factors such as the type of land and the specific design of the house.

For example, if you're building on a swampy or unstable terrain, you may need to use more cement to stabilize the structure. Similarly, if you opt for a more complex design with thicker walls or additional features, the number of cement bags required will increase accordingly.

Additionally, the quality of the cement and the skill of the builders can also impact the overall quantity needed.

To ensure you have an accurate estimate, it's advisable to consult with a professional builder or contractor who can provide a detailed assessment based on your specific requirements and local conditions.

The phases of constructing a 3-bedroom flat

Constructing a 3-bedroom flat is a complex process that can be divided into several phases. Here is an overview of the key phases involved in building a 3-bedroom flat:

Phase 1: Planning

The planning phase is crucial and involves gathering ideas, designing the layout, and creating detailed drawings. This stage also includes estimating the cost and determining whether the project is feasible within the given budget. It is important to have a full set of detailed drawings, including floor plans, electrical and plumbing layouts, and structural specifications.

Phase 2: Site Preparation and Foundation Work

Once the plans are finalised, the construction begins with site preparation. This includes clearing the land, levelling the ground, and laying underground connections. The foundation work involves excavating and constructing the base for the building, ensuring it can bear the weight of the structure.

Phase 3: Superstructure and Framing

In this phase, the building starts to take shape with the construction of walls and the installation of structural elements like beams and columns. The framing provides the basic structure for the flat, including the placement of doors and windows.

Phase 4: Installation of Services

This phase involves the first fix of electrical and plumbing services. Pipes for water supply, drainage, and electrical wiring are installed within the walls and secured. Any security measures, such as burglar bars, may also be installed during this phase.

Phase 5: Lock-up/Enclosed Stage

The building is now secured with the installation of windows, external doors, and wall cladding. Internally, insulation is added to the walls and ceilings, and temporary doors may be fixed to ensure security.

Phase 6: Fixing and Fit-Off

In this phase, the interior of the flat is completed. This includes plastering the walls, installing built-in cabinets, and fixing tiles in wet areas. The painting is also done, and any built-in appliances are installed.

Phase 7: Completion and Handover

The final phase involves a practical completion inspection to ensure the flat meets the required standards. Any final touches are made, and the keys are handed over to the owner, marking the end of the construction journey.

It is important to note that the construction process may vary based on specific requirements and local regulations. Additionally, regular site supervision and quality checks are essential throughout the construction process to ensure the desired outcome.

Frequently asked questions