Estimating and costing of a residential building is a vital process in construction planning. It helps determine the total cost of materials, labor, equipment, and services required to complete the project. Accurate estimation ensures that the construction stays within budget and helps avoid delays or financial losses. This guide explains the step-by-step method of estimating and costing a residential building as per standard practice.
What is Estimating and Costing in Construction?
Estimation is the process of calculating the approximate quantity and cost of all items required for a construction project. Costing involves the calculation of the actual cost based on the rates of materials, labor, equipment, and overheads. Together, estimating and costing guide decision-making, tendering, budgeting, and project management.
Objectives of Estimation
To assess the overall cost of the building
To determine quantities of materials, labor, and services
To prepare tender documents and bills of quantities
To plan cash flow and financial feasibility
To schedule procurement and resource allocation
To avoid cost overruns and manage construction risks
Types of Estimates Used in Residential Projects
1. Preliminary Estimate
Also known as a rough estimate, it is prepared in the early planning stage. Based on plinth area or built-up area, it helps in budget approval and feasibility checks.
2. Detailed Estimate
Prepared after working drawings are ready. It includes item-wise quantity take-off, rate analysis, material specifications, and total cost. Used for contract finalization and project execution.
3. Quantity Estimate
Focuses on exact measurement of quantities of each construction item. Helps in procurement and inventory control.
4. Revised Estimate
Prepared when there is a major design change or cost overrun. Reflects revised scope and updated rates.
5. Supplementary Estimate
Added to the original estimate for extra works not included earlier. Useful for design enhancements or additional features.
Methods of Estimating Building Costs
1. Plinth Area Method
Cost = Plinth area × Rate per square meter
Simple and used in early-stage planning
Includes cost of superstructure, walls, slab, and finishes
Does not account for item-wise breakdown
2. Cube Rate Method
Cost = Volume × Rate per cubic meter
Used for multi-story buildings where height impacts cost
Includes wall thickness and floor-to-floor height
3. Approximate Quantity Method
Semi-detailed method using approximate quantities of walls, roof, doors, etc.
More accurate than plinth area method
Useful for medium-scale budget estimation
4. Detailed Quantity Take-Off Method
Item-wise measurement and cost calculation based on drawings
Used for final budgeting and tendering
Time-consuming but most accurate
Step-by-Step Estimating and Costing of a Residential Building
Step 1: Study the Drawings
Obtain architectural, structural, plumbing, and electrical drawings
Understand floor plan, elevation, section, foundation details, and openings
Note building dimensions, levels, and construction materials
Step 2: Divide the Structure into Components
Break the building into parts such as foundation, plinth, superstructure, roof, etc.
Estimate for each component separately to avoid errors
Standard divisions include:
Site preparation and earthwork
Foundation (PCC, footing, backfilling)
Plinth beam and slab
Masonry walls and columns
Lintels and chajjas
Slabs, beams, staircases
Plastering and painting
Flooring and tiling
Doors and windows
Plumbing and electrical
External development
Step 3: Quantity Take-Off
Use the centerline method, long wall–short wall method, or cross-section method as suitable
Take measurements from drawings and calculate:
Length × Breadth × Depth for volume
Length × Height for area
Number of units for items like doors, taps, fans, etc.
Deduct openings for windows and doors in plastering or brickwork
Use IS 1200 for standard measurement rules
Step 4: Prepare Abstract of Quantities
List all items of work in serial order
Mention quantity, unit (m³, m², m, No.), and brief specification
Helps prepare a bill of quantities (BOQ)
| Item | Description | Quantity | Unit | Remarks |
|---|---|---|---|---|
| 1 | Earthwork in excavation | 35.00 | m³ | For foundation |
| 2 | PCC (1:4:8) | 12.00 | m³ | Below footings |
| 3 | Brickwork in 230mm wall | 45.00 | m³ | Up to lintel level |
| 4 | RCC Slab (M20) | 28.00 | m³ | Main roof slab |
Step 5: Rate Analysis
Determine cost per unit for each item by breaking it into:
Material cost (cement, sand, aggregate, steel, tiles)
Labor cost (mason, carpenter, plumber, painter)
Equipment cost (mixer, vibrators, scaffolding)
Transportation, water, and power supply
Contractor’s profit and overheads (usually 10–15%)
Use CPWD Schedule of Rates (SOR) or local market rates
Step 6: Costing of Each Item
Multiply quantity by unit rate to get total cost of each item
Sum all items to get total building cost
Include GST and contingency (5–10%) for safety margin
Add cost of external work and site development
Step 7: Final Estimate Report
Compile the following in the final estimate document:
Project title and client name
Scope and location of work
Drawings and specifications reference
Detailed quantity estimate
Rate analysis sheets
Abstract cost summary
Total cost with taxes and overheads
Remarks and approval section
Sample Cost Estimate Breakdown
| Description | Estimated Cost (INR) |
|---|---|
| Earthwork | ₹25,000 |
| Foundation and PCC | ₹45,000 |
| Brickwork | ₹95,000 |
| RCC (Footing + Slab) | ₹1,80,000 |
| Plaster and Finishes | ₹65,000 |
| Doors and Windows | ₹75,000 |
| Flooring and Tiles | ₹90,000 |
| Plumbing and Sanitary | ₹70,000 |
| Electrical Works | ₹60,000 |
| Painting | ₹40,000 |
| Site Development | ₹30,000 |
| Total Estimate | ₹7,75,000 |
Note: This is a sample estimate for a 2 BHK G+1 building (800–1000 sq. ft). Actual cost will vary based on location and design.
Tools Used for Estimating and Costing
Manual methods (Excel sheets, calculator)
AutoCAD for drawing-based measurements
MS Excel BOQ templates
Estimation software (Autodesk Quantity Takeoff, STAAD RCDC, CostX)
CPWD SOR and DSR for rate reference
Tips for Accurate Estimating and Costing
Double-check dimensions and units
Use updated market rates
Consider location-based cost variation
Account for material wastage (2–5%)
Include cost for curing, safety, and supervision
Add contingency for unforeseen work
Mistakes to Avoid
Ignoring hidden costs like taxes, water charges, etc.
Using outdated rates or unverified data
Not including labor and machinery downtime
Underestimating material wastage and transportation
Skipping site development costs
Omitting temporary works like scaffolding
FAQs on Estimating and Costing of Residential Building
What is the most accurate method of estimation?
The detailed quantity take-off method is the most accurate as it accounts for each item based on drawings and specifications.
How is plinth area calculated?
Plinth area = Built-up area at ground floor level including wall thickness, verandahs, and internal partitions.
What is the standard wastage percentage used in estimation?
Material wastage is typically considered as 2% for steel, 5% for concrete, and 10% for bricks and sand.
Is contingency necessary in cost estimation?
Yes, a 5–10% contingency is included to cover unforeseen expenses, price escalation, and minor scope changes.
Which software is used for construction cost estimation?
Common tools include MS Excel, AutoCAD for drawing reference, and specialized software like CostX, CANDY, and Estimator360.
How much does it cost to build a 1000 sq. ft house in India?
Depending on location and materials, it can range from ₹12 lakh to ₹18 lakh for a standard RCC framed building with finishes.
