Party Fence Wall Boundary Calculator

How the Party Fence Wall Boundary Calculator Works

This calculator determines the location of a party fence wall or fence relative to the calculated boundary (centre of the party wall) and thickness of a party wall using reveal-to-reveal and reveal-to-party-wall measurements taken from the rear elevation of adjoining properties.

What You Need to Measure

To calculate the boundary position, you need three measurements as follows:

• Measurement a — the total span between the window or door reveals on either side of the party wall
• Measurement b — from the left reveal to the left face of the party wall
• Measurement c — from the right reveal to the right face of the party wall

How the Boundary Position Is Calculated

The calculator first determines the party wall thickness by subtracting measurements (b) and (c) from the total span (a). The boundary is then assumed to lie at the centre of the party wall. This boundary location is calculated from each reveal position, giving you the distance from each reveal to the boundary.

Fence Post & Garden Wall Mode

If you are uncertain of the location of a fence post or garden wall in relation to the boundary, you can also enter the fence post / garden wall position and thickness. The calculator will show the relationship of the fence post / garden wall to the calculated boundary — useful for determining whether a fence or garden wall sits on the boundary, or to one side.

When Do You Need This Calculation?

Party wall surveyors use this calculation when preparing a party wall award under the Party Wall etc. Act 1996. Determining the boundary position is essential when recording the condition of a party fence wall or assessing whether proposed works affect the boundary. For a refresher on the difference between a party wall, party fence wall and boundary wall, see our guide to what a party wall is.

Need professional party wall advice? Contact Grey & Associates — experienced party wall surveyors serving London and the South East. We act on boundary and party fence wall matters across West London, including Kensington, Chelsea and Chiswick. Where the boundary turns out to be a party fence wall, the case follows the usual route: a party wall notice, a schedule of condition recording the wall's existing condition, and then the award.