PERIMETER/FLOOR AREA 

We have already seen that the plan shape directly conditions the enclosing walls. The Perimeter/Floor area Ratio allows us to compare different plans to establish the more economical proposal.

The lower the ratio, the more economical will be the proposal. Circular buildings have the best ratio but savings are more than offset by the higher cost of circular work.

Let us once again look at a practical example:

Assuming that both buildings have an identical floor to ceiling height of 3.00m then the:

PERIMETER/FLOOR AREA RATIO FOR:

BUILDING A

= AREA OF ENCLOSING WALLS ÷ TOTAL FLOOR AREA
= 50m x 3m ÷ 100m²
= 1.50

BUILDING B

= AREA OF ENCLOSING WALLS ÷ TOTAL FLOOR AREA
= 40m x 3m ÷ 100m²
= 1.20

It should be borne in mind that the perimeter cost can be in the order of 20% to 30% of total cost and an external wall is normally almost twice as expensive as an internal partition.

Once again we should keep other design criteria in mind but the Perimeter/floor area ratio does allow the more experienced client to state the optimum ratio (from analysis of similar buildings erected in the past) as part of the design criteria during his brief to the Architect.

Fullness on Plan

Circulation Space