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Waterproofing Paint Requirement Calculator

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The rougher the floor, the more adhesive (primer] is required, up to 1.5 times more.

Please check.

  • Laitance (impurities] and dust must be completely removed from the floor surface. If the cleaning is poor, the waterproofing layer may lift from the floor.
  • Avoid application on days when rain is forecast or humidity is 85% or higher. Air bubbles may form during the drying process, reducing waterproofing performance.
  • Corners and areas around drains are prone to cracking, so be sure to reinforce them with waterproof tape or sealant before starting the main work.
  • If the intermediate agent is applied too thickly at once, the inside may not harden. It is recommended to apply it in two stages according to the area.
  • When mixing the waterproofing agent, you must stir thoroughly with an electric mixer for 3 to 5 minutes. If not mixed properly, certain areas will never harden.

How about this calculator?

Waterproof Paint Quantity Calculator, Urethane Roof Waterproofing Quantity Calculation Guide

Rooftop waterproofing work consists of three stages: primer, intermediate coat (main waterproofing layer], and top coat. In particular, the intermediate coat, which determines waterproofing performance, requires precise calculation as the required quantity varies significantly depending on the application thickness. This calculator precisely calculates the weight of paint (kg] required for each stage by taking into account the rooftop floor area, target thickness, and floor condition.

Waterproof Paint Step-by-Step Calculation Formula

Urethane waterproofing is calculated for each stage by applying the formula for the required amount per square meter.

Required amount of intermediate (main waterproofing agent]
Required Weight (kg] = Floor Area (㎡] × Thickness (mm] × Specific Gravity (approx. 1.3]

As the most important waterproofing layer, approximately 4 kg of material is required per square meter for a standard 3 mm application.

Required amount of primer and topcoat
Undercoat (kg] = Floor Area (㎡] × Condition Coefficient / Topcoat (kg] = Floor Area (㎡] × 0.3

The primer is variable depending on the floor condition for adhesion, while the topcoat is calculated proportionally to the area for UV protection.

Detailed Guide to Calculator Input Items

Please check the construction environment and target thickness for accurate quantity calculation.

1. 1. Bottom width / length

Enter the actual width and length of the rooftop floor to be waterproofed in meters (m].

2. 2. Selection of Installation Thickness

Choose from 3mm (Standard/Recommended], 2mm (Simplified], or 1mm (Coating]. We strongly recommend 3mm application for perfect waterproofing.

3. 3. Select Floor Condition

Select Normal for standard floors, and Rough/Aged for floors with a crumbly or aged surface. The primer requirement is increased by 1.5 times for aged floors.

Material Characteristics and Recommended Requirements by Waterproofing Level

division Key roles Consumption per pyeong (kg] note
Hado (Primer] Strengthening adhesion between the floor and the middle layer 0.3 ~ 0.6 Differential application based on floor condition
Intermediate (Urethane] Formation of the actual main waterproofing layer Approx. 4.0 (based on 3mm] Calculated by applying a specific gravity of approximately 1.3
Top coating Moderate protection and UV protection About 0.3 Based on a single thin coat

Expert Know-how and Checklists

This is the key practical point that determines waterproof performance.

  • Check floor dryness (moisture content].

    Please apply the waterproofing layer only after at least 3 to 4 consecutive days of clear weather have passed since the rain, ensuring the ground is completely dry. If you cover the surface while it is still damp, the waterproofing layer may swell and burst.

  • The importance of sub-work

    If the floor is loose, you must apply a generous amount of primer to firmly secure it. If the primer seeps in and disappears quickly, it is recommended to apply it one more time to ensure adhesion.

  • Intermediate construction divided into two phases

    The standard construction method to prevent air bubbles and poor curing is to first apply a thin layer to fill holes in the floor, and then apply a second layer to increase the thickness the next day.

Frequently Asked Questions (FAQ]

  • Q. How many kilograms is 1 mal (set]?
  • A. Intermediate coats are typically sold as 18–20 kg sets, while base and top coats are sold as 14–16 kg sets (base + hardener]. Please be sure to check the set weight when purchasing.
  • Q. Are rooftop railings (parapets] also included in the calculation?
  • A. Yes, to prevent rainwater infiltration, it is safe to prepare materials with a margin of about 10 to 20 percent in the floor area, taking into account the height of the railing.
  • Q. What should I do about cracks in the floor?
  • A. After applying the primer, you must thoroughly fill the gaps with urethane sealant. Do not use regular silicone, as it does not adhere to urethane.