APS, the outline design stage: deliverables, cost estimate and first commitment on cost

APS follows the client's approval of the concept design. It deepens the project on three fronts at once: architectural, in the precision of the drawings; technical, in the choice of construction systems; and economic, in the structuring of the estimate.

It is at the end of APS that a design team under loi MOP enters its commitment to a provisional forecast works cost, with a contractual tolerance. That commitment is a legal act of some weight: it governs the construction stage fees should there be an overrun for which the design team is answerable.

• ℹ Floor plans, sections and elevations at 1:100 to 1:200: precise enough to characterise the project architecturally. Openings are located, floor-to-ceiling heights are stated, circulation is drawn.
• ℹ Outline description: a description by trade of the materials and methods envisaged, for instance reinforced concrete frame, accessible flat roof, thermally broken aluminium joinery, external wall insulation.
• ℹ Preliminary fire safety note: where the project is a public-access or high-rise building, a preliminary note is produced to anticipate the regulatory constraints.

• ℹ APS estimates for the technical packages: the structural, mechanical and electrical consultants produce their estimates in step with the architectural assumptions that have been settled.
• ℹ Target cost by technical package: an internal working document confirming that the package envelopes hold together within the overall envelope.

The APS estimate is the economic centre of the stage. It is structured by trade or by functional element, unlike the ESQ, which used global ratios per square metre. That structure makes the cost items visible and allows trade-offs to be prepared if the envelope is exceeded.

A typical APS estimate structure

Earthworks and external services: excavation, foundations, external networks, landscaping. 5 to 12 % of the works cost depending on the site.

Structural works: reinforced concrete frame, loadbearing masonry, roof structure, ground-bearing slab. 25 to 35 % of the works cost.

Roofing and waterproofing: flat roof, pitched roof, rooflights. 3 to 7 %.

Façades and external joinery: renders, cladding, external wall insulation, aluminium, timber or PVC joinery. 8 to 15 %.

Plasterwork, insulation and partitions: internal partitions, linings, suspended ceilings. 6 to 10 %.

Internal joinery and fitted furniture: internal doors, cupboards, kitchen fit-out. 3 to 6 %.

Floor and wall finishes: tiling, timber flooring, paint, wall tiles. 5 to 9 %.

Mechanical and plumbing: heating, ventilation, cooling, hot water, sanitaryware. 8 to 15 %.

Electrical, power and data: distribution boards, cabling, lighting, data, security. 6 to 12 %.

Lift, where applicable: 50,000 to 80,000 € excluding VAT per lift depending on configuration.

The accuracy of an APS estimate is in the region of ±15 to 20 %. That is markedly better than ESQ, but it remains wide. The technical choices sharpened at APD will bear directly on the final cost.

Under loi MOP, the end of APS marks the design team's first formal commitment on cost. That commitment to a provisional forecast cost carries a tolerance, generally ±10 % at APD and as much as ±20 % at APS depending on the contract.

If the final works cost exceeds the definitive forecast cost, settled at APD, beyond the contractual tolerance and for reasons attributable to the design team, penalties can be applied to the construction stage fees, on the direction of the works in particular. It is therefore fundamental that the APS estimate be realistic rather than optimistic.

ℹ The trap of an under-stated APS estimate An APS estimate deliberately set low, to reassure a client or to win a commission, sets off a cascade. At APD the measured quantities reveal the gap against the APS envelope, forcing either a change of design or an admission of overrun. At tender the contractors' bids confirm the gap, producing friction with the client, a renegotiated appointment, sometimes an abandoned project. And in construction, if the project proceeds on an insufficient envelope, the specification is cut, the finishing trades are degraded, and disputes follow. An honest APS estimate is the construction economist's first act of professionalism.

On refurbishment work, APS begins after the technical surveys of the existing building: structure, asbestos, lead, existing electrical installations. Those surveys are not part of the core appointment and must be commissioned separately by the client.

An APS estimate on a refurbishment is structurally more uncertain than on new build. The hazards of an existing building, what is discovered once work starts, the real state of the structure, the presence of hazardous materials, can generate costs nobody could foresee. The contingency must be larger than on new build, generally 10 to 20 % of the works cost.

The APS estimate is the most time-consuming cost deliverable of the design stages. Producing it requires a fine knowledge of prices trade by trade, kept current, and the ability to structure a document a client can actually use to make trade-offs.

ℹ Quostra, the construction economist on demand Cost estimates, pricing schedules, developer appraisals, summary notes. The deliverables that take you days today, taken on by a dedicated economist. You have better things to do. Submit your project and an economist takes over. → quostra.com

Sources: Léonard Hamburger, Maître d'œuvre Bâtiment, 3rd ed., Eyrolles, 2016 · MIQCP fee guide.