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Calcimator

Plaza Waterproofing Calculator

Waterproofing assembly for pedestrian plaza over occupied space.

About this calculator

Total Project Cost combines waterproofing cost (membrane, slope layer, protection board, drainage, drain assemblies, and expansion joints) with a separate finish-layer cost that depends on Finish Type. Finish Type is a binary switch with a large effect: pavers on pedestals (1, the default) cost roughly 50% MORE than a concrete topping slab (2) at this calculator's default plaza size, because per-pedestal hardware plus paver material runs higher per square foot than a 4" concrete topping slab in this model. Traffic Type (1= pedestrian, 2=light vehicular, 3=heavy vehicular) changes both membrane thickness (120/180/ 215 mils) and its per-square-foot cost, and the two move together in the same direction -- heavier traffic always costs more, with heavy vehicular running roughly 22% above pedestrian at this calculator's defaults.

Plaza Length and Plaza Width both move essentially every output (membrane area, slope layer volume, drainage composite, and every cost figure) since Plaza Area is their product, though Plaza Length has a somewhat larger effect than Plaza Width at this calculator's default 100x60 ft plaza, since the plaza is not square and the perimeter-driven membrane turn-up scales slightly differently with each dimension. Number of Drains and Expansion Joints (linear ft) both move cost only modestly relative to plaza size or finish/traffic type -- through drain assembly cost and expansion-joint treatment cost, respectively.

Inputs

ft
ft

Results

Membrane area (sq ft)

7,311

Membrane thickness (mils)120
Slope layer (cu yd)111.1
Drainage composite (sq ft)6,300
Waterproofing cost ($)$90,043.00
Total project cost ($)$169,543.00
Cost per sq ft ($)$28.26
How to Use This Calculator
  1. Enter Plaza Length (ft) and Plaza Width (ft) — the total occupied-space deck area to be waterproofed.
  2. Select Traffic Type (1=pedestrian, 2=light vehicular, 3=heavy vehicular) to determine membrane thickness requirements.
  3. Enter Number of Drains and Expansion Joints (linear ft) requiring waterproof detailing.
  4. Choose Finish Type (1=pavers on pedestals, 2=concrete topping slab) to complete the assembly cost estimate.
  5. Review Membrane Area (sq ft), Membrane Thickness (mils), and Slope Layer (cu yd) for material ordering.
  6. Use Waterproofing Cost and Total Project Cost to validate the budget before design development.

How the result changes with Plaza length (ft)

Plaza length (ft)Membrane area (sq ft)
503,783
755,547
15010,839
25017,895

What each input means

Plaza length (ft)
Length of the plaza deck area.
Plaza width (ft)
Width of the plaza deck area.
Traffic (1=ped, 2=light veh, 3=heavy)
1 = Pedestrian only. 2 = Light vehicular (cars). 3 = Heavy vehicular (trucks/fire apparatus).
Number of drains
Plaza drain assemblies. Rule of thumb: 1 per 1,000 sq ft minimum.
Expansion joints (linear ft)
Linear feet of expansion/control joints requiring waterproof treatment.
Finish (1=pavers, 2=topping slab)
1 = Pavers on adjustable pedestals. 2 = Concrete topping slab.

What each result means

Membrane area (sq ft)
Total waterproofing membrane including flashings and waste.
Membrane thickness (mils)
Recommended membrane dry film thickness based on traffic loading.
Slope layer (cu yd)
Lightweight concrete or tapered insulation for drainage slope.
Drainage composite (sq ft)
Geocomposite drainage layer area.
Waterproofing cost ($)
Membrane, slope layer, protection, drainage, and drains.
Total project cost ($)
Complete assembly including finish surface.
Cost per sq ft ($)
Total project cost per square foot of plaza.

How this is calculated

Worked example, using the default values

  1. Identify Input Parameters
    4 parameters
    Plaza length (ft) = 100, Plaza width (ft) = 60, Traffic (1=ped, 2=light veh, 3=heavy) = 1, Number of drains = 6 = 6 input(s) provided
  2. Calculate Membrane area
    Membrane area = totalMembraneArea * 1.12
    7311 = 7311
  3. Calculate Membrane thickness
    120 = 120
  4. Calculate Slope layer
    Slope layer = (plazaArea * (avgSlopeDepthIn / 12)) / 27
    111.1 = 111.1

Engine last updated . Checked against 2 independently-derived tests — how we verify calculators. Built by Paul Gunder, a software engineer, not a licensed financial, medical, or legal professional.

Frequently Asked Questions

Is a topping slab always cheaper than pavers on pedestals?

At this calculator's default 100x60 ft plaza, yes -- pavers on pedestals (Finish Type 1) cost roughly 50% more than a concrete topping slab (Finish Type 2), because the per-pedestal hardware plus paver material runs higher per square foot than a 4" concrete topping slab in this model. Pavers do offer easier future access to the waterproofing membrane below for repairs, which this cost figure doesn't capture.

How much more does heavy vehicular traffic cost than pedestrian-only?

Roughly 22% more in Total Project Cost at this calculator's defaults. Traffic Type changes both the required membrane thickness (120 mils for pedestrian, up to 215 mils for heavy vehicular) and the per-square-foot membrane cost, and both move in the same direction as traffic loading increases, so the two effects compound rather than offset.

Do Plaza Length and Plaza Width affect cost the same way?

Nearly, but not exactly -- both scale essentially every output since Plaza Area is their product, but Plaza Length has a somewhat larger measured effect than Plaza Width at this calculator's default 100x60 ft (non-square) plaza, because the perimeter-driven membrane turn-up area scales slightly differently with each dimension when the plaza isn't square.

Do drains and expansion joints matter much for the budget?

They move Total Project Cost, but only modestly compared to plaza size, traffic type, or finish type. Each additional drain adds a fixed per-assembly cost, and each additional linear foot of expansion joint adds a fixed per-foot treatment cost -- real, but small next to the effect of doubling the plaza's footprint or switching finish types.

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