What Does a Quantity Surveyor Actually Do?

If you’re planning a build – whether it’s a one-off home, an extension, or a multi‑million euro development – you’ll quickly discover that managing costs is one of the hardest parts of the process. That’s where a Quantity Surveyor (QS) comes in.

A Quantity Surveyor is a construction cost specialist. Their job is to make sure your project is financially viable, accurately priced, and kept under control from the first sketch to the final account.

At Crawford QS, we specialise in residential construction and general estimation. Below, we break down what a QS actually does in practical terms for architects, developers, builders, and homeowners.

1. Turning Ideas into Realistic Budgets

Every project starts with an idea – but ideas need numbers.

A QS takes your drawings, specifications, and project brief and turns them into a realistic cost plan. This includes:

• Estimating the total cost of the project

• Breaking costs down into clear elements (foundations, structure, finishes, services, etc.)

• Highlighting key cost drivers and risks

• Advising where savings can be made without compromising quality

For developers and architects, this early cost planning helps test the feasibility of a project before too much time or money is committed. For homeowners, it provides clarity: “Can we actually afford this?” and “What level of finish is realistic for our budget?”

2. Preparing Bills of Quantities and Tender Documents

One of the core tasks of a Quantity Surveyor is preparing a Bill of Quantities (BOQ).

A BOQ is a detailed, itemised breakdown of all the measurable work on a project. It sets out quantities and descriptions of materials, labour and trades, so that builders can price the same information on a like‑for‑like basis.

A QS will typically:

• Measure the project from drawings and specifications

• Prepare a BOQ and/or detailed pricing schedule

• Help assemble a clear tender package (drawings, spec, BOQ, preliminaries)

For clients, this achieves two crucial things:

1. Comparable quotes – all builders are pricing the same scope.

2. Reduced disputes later – because the scope is clearly defined upfront.
   

3. Supporting Tendering and Contractor Selection

Once the tender documents are ready, the QS helps you run a structured tender process.

This can include:

• Advising which contractors to invite to tender

• Answering tender queries and clarifying scope

• Analysing returned tenders and checking for errors or omissions

• Preparing comparison summaries so you can see who is genuinely competitive

• Advising on negotiations and contract award

For builders, a QS can also work on the other side – helping them prepare accurate, competitive tenders so they win more of the right work and avoid under‑pricing jobs.

4. Managing Costs During Construction

A QS doesn’t just disappear once the builder is appointed. Cost management during construction is a major part of the role.

Typical responsibilities include:

• Valuing work done on site for interim payments

• Tracking costs against the original budget and reporting variances

• Assessing and negotiating variations and claims

• Advising on the cost impact of design changes

• Preparing cashflow forecasts and cost reports

• Agreeing the final account at the end of the project

For private clients and residential developers, this provides ongoing reassurance that the project is financially under control. For architects, it helps manage client expectations and avoid difficult conversations when costs drift.

5. Reducing Risk and Preventing Disputes

Many disputes in construction arise from unclear scope, poor documentation, or misunderstandings about cost.

A good Quantity Surveyor helps prevent these problems by:

• Ensuring the tender documents are clear and complete

• Recording agreed changes and their cost implications

• Providing an independent view on claims and variations

• Keeping all parties aligned on budget and expectations

By tracking costs and documenting decisions, the QS acts as a buffer between client, architect, and builder – reducing the chances of disagreements and protecting relationships.

6. How a QS Helps Different Types of Clients

Architects & Designers

• Helps manage client expectations on cost

• Provides cost checks at key design stages

• Supports smoother tendering and contract administration

• Reduces the risk of projects being shelved due to budget issues

Developers & Larger Builders

• Provides robust cost plans and BOQs for projects in the €1m–€20m range

• Improves the accuracy of tenders and financial appraisals

• Supports funding applications with credible cost information

• Manages budgets and subcontractor accounts during construction

Homeowners & Small Builders

• Helps homeowners understand and compare quotes properly

• Advises on what should be included in a tender package

• Supports small builders with accurate pricing and tender submissions

• Provides independent oversight of costs during the build

7. Do You Need a Quantity Surveyor?

If your project has a budget, you can benefit from a QS.

Whether you’re an architect trying to keep a client’s design on budget, a developer assessing viability, a builder tendering for work, or a homeowner planning a once‑off build, a Quantity Surveyor gives you:

• Clarity on what your project will really cost

• Confidence that tenders are fair and comparable

• Control over costs as the project progresses

At Crawford QS, we specialise in residential construction and support clients across Dublin and Ireland with cost planning, BOQ preparation, tender support, and construction cost management.

If you’d like to discuss an upcoming project or need help understanding your costs, get in touch and we’ll be happy to talk it through.