CALCULATING MAKING USE COSTS

(Often incorrectly referred to as enclosure costs). 

​Determining the correct costs under Section 11(11) of the Party Wall Act can become complex. 
​
Here's a simplified guide to calculating them.

Understanding Section 11(11) of the Party Wall Act

Section 11(11) states:

When an adjoining owner uses a wall built at the expense of the building owner, they must pay a 50% contribution (usually) based on the cost of the work as if it were done at the time of use.

Key Points for Calculating Enclosure Costs

Work out which costs to Include. Consider the following:

• Is some of the original party wall being used?
  
• How much of the wall is to be made use of? 
  
• Were new foundations required?
  

Case Study 1: Single Storey Rear Extension

 Scenario:
In E17 East London, a building owner built an extension, creating a new party wall astride the boundary. The adjoining owner now wants to build a mirror image extension.

​Costs to include:

• Contribution to professional fees
• Contribution to site set up costs
• Excavations for new foundation incl. removal of spoil
• Concrete for new foundations
• Cavity brick and block wall with insulation
• Raised parapet wall 150mm beyond height of proposed roof
• Coping stones

Case Study 2: Loft extension

​Scenario:
 In SW6 South West London, a building owner raised a party parapet wall to create a new loft extension. The adjoining owner now wants to build a mirror image extension.

​Costs to include:

• Contribution to professional fees
• Contribution to site set up costs including scaffolding
• Solid brick wall
• Raised parapet wall 150mm beyond height of proposed roof
• Coping stones

Calculation method

​There are a number of ways to calculate costs.

1. Use a per square metre rate. This is quick, easy and reasonably accurate. Websites like Checkatrade can be helpful in establishing market rates based on real world data. This method can be used by the parties with little or no input from the surveyors if required. 
2. Obtain quotes from the builders (previous and proposed). This method can be used by the parties with little or no input from the surveyors if required. 
3. Calculate the cost of labour and materials. Requires sufficient practical knowledge of construction to be accurate. Can be done by the surveyor/s where the parties have not come to an agreement. Will incur additional cost/s. Not cost effective for small sums.
4. Hire a Quantity Surveyor. Will take extra time. Will come at an additional cost. Not cost effective in most cases. 
5. Use the Building Cost Information Service (BCIS). Not available to the public. Requires surveyor to have a subscription. Very few party wall surveyors have this. Not cost effective in most cases.