How to Deal with Unexpected Issues During a Building Project

Introduction

One of the most common sources of stress in residential building projects isn't poor craftsmanship or bad communication — it's unexpected discoveries. The wall that turns out to be load-bearing. The drain that's in the wrong place. The rotting timbers discovered when the loft floor is opened up. The asbestos found during the strip-out.

Unexpected issues are genuinely unpredictable — and they happen on most significant building projects at some point. The difference between a project that handles them well and one that doesn't usually comes down to three things: how the contractor communicates when they discover the issue, how the contract handles variations, and how the client responds.

This guide sets out how to deal with unexpected discoveries professionally and without unnecessary conflict.

How a Good Contractor Communicates Unexpected Issues

When an unexpected issue is discovered on site, the first responsibility is clear communication. A professional contractor should:

Stop the affected work immediately if proceeding could cause further damage or create a safety risk
Document the discovery with photos before anything is disturbed
Notify the client clearly and promptly — what was found, where, and what the implications appear to be
Present the options for how to proceed, including the cost and programme implications of each
Wait for client instruction before proceeding where the issue involves significant additional cost

A contractor who proceeds without telling you, or who presents a significant variation invoice at the end of the project without prior discussion, is not handling the process correctly.

The Importance of the Variation Process

Most construction contracts include a variation procedure — a mechanism for agreeing changes to the original scope, including changes driven by unexpected discoveries.

A proper variation process involves:

The issue is identified and communicated
The contractor provides a written assessment of the options and costs
The client approves (or declines, or asks for alternatives) in writing
The agreed additional work is carried out
The variation is added to the running cost account

If you're not operating within a written contract, or if your contract doesn't have a variation procedure, this process becomes a matter of good faith rather than contractual obligation. This is one of many reasons why having a proper written contract from the start matters.

Common Unexpected Discoveries on London Building Projects

Rotting or inadequately sized roof timbers. Particularly common on Victorian and Edwardian properties. When a loft conversion opens up the existing roof structure, damaged or undersized timber may be discovered that requires replacement or reinforcement.

Hidden chimneys or structural elements. Many Victorian terraces have hidden structural elements — chimney breasts that were plastered over, supporting walls that weren't obvious from the drawings. These are revealed during strip-out and may affect the structural approach.

Asbestos. Properties built before 2000 may contain asbestos in various forms — artex ceilings, pipe lagging, roofing felt, floor tiles. If asbestos is suspected, work must stop and an asbestos survey carried out before proceeding. Removal requires licensed contractors.

Drainage in unexpected positions. Drains found in different locations from what was assumed in the design. This can affect foundation positioning and require design changes before foundations are dug.

Poor existing workmanship. Previous extensions or alterations done without Building Regulations approval may be revealed during the project. Bringing this up to standard adds scope and cost.

How Clients Should Respond

The client's role when an unexpected issue arises is to:

Stay calm and focus on the decision at hand, not the disruption
Ask for the options to be clearly explained before agreeing to anything
Request a written variation proposal with the cost broken down
Refer to the contingency you (should have) held back for exactly this purpose
Make a decision within a reasonable timeframe to avoid compounding the delay

An unexpected issue is not, in most cases, evidence of a contractor cutting corners or deceiving you. It's usually evidence that the condition of an old building is imperfectly known until it's opened up.

Working with a contractor who communicates well under pressure?
RCB Design & Build manages unexpected discoveries professionally — with clear communication, written variation proposals, and client-led decision-making before any additional work proceeds. Contact us.