Delay Analysis Methods in Construction: 5 Approaches Explained

<div class="ge-article-wrapper"> <nav class="ge-toc" aria-label="Table of contents"> <p class="ge-toc-label">In this article</p> <ul class="ge-toc-list"> <li><a href="#the-five-methods-at-a-glance">The Five Methods at a Glance</a></li> <li><a href="#how-each-method-works">How Each Method Works</a></li> <li><a href="#worked-example-25m-rail-depot-3-months-late">Worked Example: £25M Rail Depot, 3 Months Late</a></li> <li><a href="#how-evm-data-supports-delay-claims">How EVM Data Supports Delay Claims</a></li> <li><a href="#common-mistakes">Common Mistakes</a></li> <li><a href="#frequently-asked-questions">Frequently Asked Questions</a></li> </ul> </nav> <article class="ge-article-body"> <p>Delay analysis is the process of determining the cause, responsibility, and impact of schedule delays on a construction project. It sounds academic. It isn't. On a £25M project running 3 months late, the difference between "contractor delay" and "employer delay" can be worth £1M or more.</p> <p>There are five recognised methods for delay analysis in UK construction, each with different strengths, data requirements, and credibility with adjudicators.</p> <p>This page is part of the <a href="/en/earned-value/definitions">earned value definitions glossary</a>. For the full formula reference, see the <a href="/en/earned-value/formulas">earned value formulas page</a>.</p> <h2 id="the-five-methods-at-a-glance">The Five Methods at a Glance</h2> <div class="ge-table-wrap ge-anim"><table class="ge-table"> <thead> <tr><th>Method</th><th>Timing</th><th>Complexity</th><th>Best For</th></tr> </thead> <tbody> <tr><td>As-Planned vs As-Built</td><td>Retrospective</td><td>Low</td><td>Simple disputes, low-value claims</td></tr> <tr><td>Impacted As-Planned</td><td>Prospective or retrospective</td><td>Medium</td><td>Quick early assessments</td></tr> <tr><td>Collapsed As-Built</td><td>Retrospective</td><td>High</td><td>Post-completion claims</td></tr> <tr><td>Time Impact Analysis (TIA)</td><td>Contemporaneous</td><td>High</td><td>High-value, complex claims</td></tr> <tr><td>Windows Analysis</td><td>Retrospective</td><td>Very high</td><td>Major disputes, adjudication/litigation</td></tr> </tbody> </table></div> <h2 id="how-each-method-works">How Each Method Works</h2> <h3>1. As-Planned vs As-Built</h3> <p>The simplest approach. Compare the baseline programme against what actually happened.</p> <h3>2. Impacted As-Planned</h3> <p>Take the baseline programme and insert the delay events to model their theoretical impact.</p> <h3>3. Collapsed As-Built</h3> <p>Start with what actually happened (the as-built programme), then remove delay events one by one.</p> <h3>4. Time Impact Analysis (TIA)</h3> <p>The gold standard. Insert delay events into the programme at the point they occurred.</p> <h3>5. Windows Analysis</h3> <p>Divide the project timeline into "windows" (typically monthly periods) and analyse delay within each window separately.</p> <h2 id="worked-example-25m-rail-depot-3-months-late">Worked Example: £25M Rail Depot, 3 Months Late</h2> <span class="ge-worked-label">Worked Example</span> <div class="ge-callout ge-anim"> <p><strong>Scenario:</strong> A £25M NEC4 Option C rail maintenance depot in Birmingham. Planned Completion was 20 December 2025. Actual completion was 18 March 2026, 88 days late.</p> <p><strong>Three delay events identified:</strong></p> <div class="ge-table-wrap ge-anim"><table class="ge-table"> <thead><tr><th>Event</th><th>Duration</th><th>Cause</th><th>Risk</th></tr></thead> <tbody> <tr><td>D1: Design changes to drainage</td><td>35 days</td><td>Client instruction (CE)</td><td>Employer</td></tr> <tr><td>D2: Steelwork fabrication delay</td><td>28 days</td><td>Subcontractor performance</td><td>Contractor</td></tr> <tr><td>D3: Exceptional weather</td><td>22 days</td><td>Weather event (CE under 60.1(13))</td><td>Employer</td></tr> </tbody> </table></div> <p><strong>TIA result:</strong> D1: 35 days, D2: 16 days net (minus 12 days concurrency), D3: 22 days. Float consumed: 3 days.</p> <p><strong>Entitlement:</strong> 57 days extension of time. Prolongation costs for 45 days. 45 days x £8,200/day = <strong>£369,000</strong>.</p> </div> <h2 id="how-evm-data-supports-delay-claims">How EVM Data Supports Delay Claims</h2> <p>Your EVM data produces an <a href="/en/earned-value/definitions/schedule-performance-index">SPI</a> trend over time. That trend is quantitative evidence of when the project started falling behind. It's not a substitute for proper delay analysis, but it's powerful corroborating evidence.</p> <h2 id="common-mistakes">Common Mistakes</h2> <ol> <li><strong>Using the wrong method for the situation.</strong> Match the method to the value and complexity.</li> <li><strong>Not maintaining contemporaneous programme updates.</strong> TIA requires the programme status at the time each delay event occurred.</li> <li><strong>Ignoring concurrency.</strong> Address concurrency head-on in your analysis.</li> <li><strong>Treating EVM data as a substitute for delay analysis.</strong> SPI and SV are indicators, not proof.</li> </ol> <div class="ge-product-note ge-anim"> <p><strong>How Gather helps.</strong> Gather's AI reads your site diaries daily and maps progress against your cost-loaded programme. <a href="https://gatherinsights.com/contact">Book a demo</a> to see it working on a live NEC4 project.</p> </div> <h2 id="frequently-asked-questions">Frequently Asked Questions</h2> <h3>Which delay analysis method is best?</h3> <p>There's no single best method. The SCL Protocol recommends Time Impact Analysis as the preferred approach where contemporaneous programme updates exist.</p> <h3>How does delay analysis work on NEC4 contracts?</h3> <p>NEC4's compensation event process is essentially built-in delay analysis. Clause 63.5 uses the Accepted Programme to model the delay impact.</p> <h3>Can EVM data prove delay?</h3> <p>Not on its own. But <a href="/en/earned-value/definitions/schedule-performance-index">SPI</a> trends provide strong corroborating evidence.</p> <h3>What records do I need for delay analysis?</h3> <p>At minimum: the baseline programme, progress records, correspondence about delay events, and the as-built programme.</p> </article> </div>