Feasibility Cost Planning for Apartment Developments: What Developers Should Model Early

A multi-storey apartment development can look strong on paper and still unravel later if the feasibility budget is built on optimistic assumptions. The goal of feasibility cost planning isn’t to produce a single “perfect” number - it’s to build a realistic cost model early enough that you can make confident decisions on land, design, procurement and programme.

Below is what developers should model early, why feasibility budgets commonly fail, and how a Quantity Surveyor (QS) helps turn a rough appraisal into a bankable, tender-ready cost plan.

Why feasibility budgets fail

Feasibility budgets usually fail for two reasons: assumptions that don’t hold and allowances that were never included.

Common assumption traps include:

• Using outdated €/m² rates without adjusting for specification, height, complexity, or market conditions.

• Assuming programme durations that don’t reflect local constraints (access, neighbours, working hours, deliveries).

• Underestimating preliminaries and site overheads, which are highly sensitive to time.

• Treating “provisional” items as if they’ll come in at the low end.

The missing-allowance problem is even more damaging. Early appraisals often focus on the obvious construction cost and ignore the “project reality” costs that can shift feasibility materially: enabling works, services, statutory requirements, contributions, and time-related costs.

Structural Frame Analysis

What “frame analysis” means (in plain English)

When people say “frame analysis”, they’re talking about comparing the structural options and how each option affects:

• Build cost (materials, labour, specialist trades)

• Programme (how quickly floors can be cycled, curing times, lead times)

• Preliminaries (site management, cranes/hoists, welfare, temporary works)

• Risk (design coordination, tolerances, supply chain)

For multi-storey developments, the most common comparisons are:

• Reinforced concrete (RC) frame: Can be very fast to erect but can be costly in comparison to other options.

• Traditional blockwork and vertical ties: Very slow but can be very competitive in terms of cost, however one must consider the programme elongation in comparison to RC/steel/pre-cast. It is a very labour-intensive option. It is an option that is being phased out.

• Pre-cast walls and hollowcore slabs: can be fast to erect and competitive when the programme savings are considered.

• Steel frame: can be fast to erect, but lead times, fire protection, and coordination can shift the overall cost.

A good frame analysis doesn’t just compare “structure cost”. It compares the total effect on the project - especially the knock-on impact on time and preliminaries.

Cost headings developers forget (and why they matter)

These are the headings that frequently get under-allowed at feasibility stage:

• Enabling works: demolition, site clearance, remediation, temporary works, hoarding, surveys, and early diversions.

• Utilities and services: ESB/Irish Water connections, upgrades, diversions, substations, wayleaves, and lead times.

• Drainage and attenuation: on-site drainage complexity, attenuation tanks, pumping, outfalls, and testing.

• Access and logistics: road openings, traffic management, delivery restrictions, crane strategy, storage constraints, neighbour interfaces.

• Statutory requirements and contributions: local authority requirements, planning conditions, bonds, and any applicable contributions.

• Inflation and market movement: tender price inflation, volatility in key packages, and procurement timing.

• Finance/time-related costs: preliminaries driven by programme length, plus the cost of delay (extended overheads, professional fees, rework, and opportunity cost).

If these headings aren’t modelled early, feasibility can look healthy until the first “real” cost plan or tender returns — and then the scheme has to be redesigned under pressure.

How a QS builds a feasibility cost plan (and uses sensitivity ranges)

A QS feasibility cost plan is a structured model that links design decisions to cost outcomes. Typically it includes:

1. Scope definition

What’s included and excluded, what’s assumed, and what’s still unknown.

2. Elemental cost plan

Costs broken down by building elements (substructure, frame, envelope, MEP, finishes, external works) rather than a single blended rate.

3. Project-specific allowances

Enabling, services, drainage, logistics, statutory items, and risk allowances.

4. Preliminaries and programme logic

A preliminaries model that reflects the likely programme, site constraints and procurement route.

5. Risk and contingency

Not a “flat % for everything”, but a contingency aligned to what’s actually unknown.

6. Sensitivity ranges

Instead of one number, you get a range (e.g., low/base/high) based on key drivers such as frame choice, specification, programme length, and services scope.

Sensitivity is what makes a feasibility plan decision-ready. It answers questions like:

• What happens if the programme extends by 8–12 weeks?

• What if services upgrades are required?

• What if we shift from RC to steel, or change the façade specification?

When to run feasibility cost planning

Developers get the most value when feasibility cost planning is done early and updated at key decision points:

• Pre-offer / pre-acquisition: to stress-test the land deal and identify major cost risks.

• Pre-planning: to align design intent with a realistic budget before the scheme hardens.

• Pre-tender: to ensure the tender pack is complete, allowances are realistic, and the procurement strategy matches the market.

Final thought

Feasibility isn’t a one-off spreadsheet — it’s a living model that should become more accurate as the design develops. The earlier you build a proper cost plan (with clear assumptions and sensitivity), the fewer “surprises” you’ll face when the project meets the real world.

If you’re assessing a multi-storey opportunity and want a feasibility cost plan that stands up to scrutiny, a QS can help you model the right headings early — and make decisions with confidence.