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Section 18 diminution valuation

Section 18 of the Landlord and Tenant Act 1927 caps the landlord's recovery at the diminution in the value of the reversion caused by the breaches. The single most powerful provision in tenant-side dilapidations defence.

Author
CBC Surveyors
Updated
Updated 2026
Reading time
6 min read

Overview

The cost of carrying out the works in a schedule of dilapidations is one number. The amount the landlord can actually recover is, ultimately, a different number, and it is set by Section 18. Diminution valuation is the discipline of working out what that recoverable sum actually is.

First limb: cap on damages

The first limb of Section 18(1) provides that damages for breach of a covenant to repair shall not exceed the diminution in the value of the reversion caused by the breach. Even if the cost of works is, say, £200,000, recovery is capped at the diminution figure, which can be materially lower or, in some cases, nil.

Second limb: superseded works

The second limb of Section 18(1) prevents recovery where the landlord has, at or shortly after lease end, demolished or structurally altered the premises in a way that makes the repair works valueless. In practical terms, refurbishment or redevelopment that supersedes the schedule items often defeats the claim on those items entirely.

How diminution is assessed

Diminution is assessed by reference to the value of the landlord's reversion in two states:

  1. Value of the reversion in the actual condition at lease end
  2. Value of the reversion in the condition required by the lease

The difference is the diminution and the cap on recovery. Establishing both figures requires valuation expertise applied to the specific property, location and market evidence.

Key takeaways

What to remember

  • 01Cost of works and recoverable sum are different numbers, often very different.
  • 02Both limbs of Section 18 can independently reduce or extinguish a claim.
  • 03Specialist diminution input is essential on any meaningful tenant-side defence.
Diminution input

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