Os House Square Footage Calculated with or Without Walls

Calculating OS house square footage with or without walls involves different measurement methods that affect the final result. This guide explains the key approaches, when to use each method, and how to interpret the results.

What is OS House Square Footage?

OS house square footage refers to the measurement of a building's interior space, typically used for real estate valuation, construction planning, and space utilization analysis. The calculation can be performed in two primary ways: including walls or excluding them, which affects the final measurement.

Key Considerations

Walls are typically included in measurements for construction purposes
Excluding walls provides a more accurate representation of usable space
Different industries use different measurement standards

Note: OS house square footage calculations are standardized by the Royal Institution of Chartered Surveyors (RICS) in the UK and similar organizations in other countries.

Methods of Calculation

There are two primary methods for calculating OS house square footage:

Method 1: Including Walls

This method measures the entire interior space including walls. It's commonly used in construction planning and real estate valuation where the structural elements are important.

Total Square Footage = Length × Width

Method 2: Excluding Walls

This method measures only the usable space, excluding walls and other non-usable areas. It's more accurate for space planning and interior design purposes.

Usable Square Footage = (Length - 2 × Wall Thickness) × (Width - 2 × Wall Thickness)

Where wall thickness is typically 4 inches (0.333 feet) for standard construction.

Calculator Usage

Use the calculator on the right to quickly determine the square footage of your OS house using either method. The calculator provides:

Accurate measurements in square feet
Comparison between both methods
Visual representation of the difference

Simply enter your room dimensions and select the calculation method to get instant results.

Comparison Table

The following table compares the results of both calculation methods for a standard 12' × 15' room with 4-inch walls.

Method	Calculation	Result (sq ft)
Including Walls	12 × 15	180
Excluding Walls	(12 - 2 × 0.333) × (15 - 2 × 0.333)	168.89

This shows a difference of approximately 11.11 square feet when excluding walls.

Frequently Asked Questions

When should I use the "including walls" method?: Use this method when you need to account for the entire structural space, such as in construction planning or real estate valuation where walls are part of the building's structure.
When should I use the "excluding walls" method?: Use this method when you're focusing on usable space, such as for interior design, furniture arrangement, or space planning where walls don't contribute to the usable area.
What is the standard wall thickness used in these calculations?: The standard wall thickness used is typically 4 inches (0.333 feet) for residential construction, but you can adjust this value in the calculator for different scenarios.
Are there any other factors that affect OS house square footage?: Yes, factors like room shape, staircases, and other architectural features can affect the final measurement. The calculator provides a basic estimate that can be adjusted for more complex spaces.
Can I use this calculator for commercial properties?: While this calculator is designed for residential properties, the same principles apply to commercial spaces. You may need to adjust for different wall thicknesses or additional architectural features.