# Why Your Exterior Door Selection Could Lead to Indoor Flooding: The Low vs. High Door Threshold Case Study

**Location/Showroom Focus:** Warren Windows & Doors Architectural Showroom  
**Presenter:** Paula (Sales Specialist – Sales05@warrenwindow.com)  
**Topic:** Exterior Door Threshold Selection, Weatherproofing, Rain Protection & Architectural Door Design  

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### EXECUTIVE SUMMARY: THE DANGERS OF IMPROPER DOOR THRESHOLD SELECTION

When designing or renovating a property, door thresholds are often treated as an aesthetic afterthought. Homeowners, builders, and designers frequently opt for sleek, low-profile, or flush thresholds to achieve a seamless transitions between indoor living spaces and outdoor patios or balconies. However, when severe weather strikes—such as sudden torrential rains, flash floods, or typhoons—an improperly specified threshold can transform your entryway into an inlet for water.

In this practical case study filmed live during a heavy rainfall event at the Warren showroom, Paula breaks down the structural differences between door threshold profiles and reveals why selecting a high threshold for exposed exterior doors is critical to protecting your interior flooring, foundation, and interior investment.

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### BREAKDOWN OF EXTERIOR DOOR THRESHOLD TYPES

Exterior doors are classified by their threshold height and structural profile. Choosing the correct type depends on location, elevation, structural overhangs, and climate conditions:

1. **No-Threshold / Flush Thresholds (0 mm):** - *Best For:* Interior transitions, covered hallways, and interior room dividers.
   - *Risk Level:* High for exterior application. Offers virtually zero barrier against wind-driven rain or rising water.

2. **Low Thresholds (~2 cm / 0.78 inches):** - *Best For:* Barrier-free accessibility (ADA compliance), mobility access, or fully covered exterior patios.
   - *Risk Level:* Moderate to High. As demonstrated in our showroom case study, low thresholds can easily be overwhelmed if outdoor drainage systems clog or ground level terrain tilts toward the entrance.

3. **Medium Thresholds:** - *Best For:* Standard sheltered residential entryways with moderate overhangs.
   - *Risk Level:* Moderate. Provides improved air and water sealing compared to low profiles, but may still fail during extreme storm conditions or prolonged heavy rainfall.

4. **High Weathered Thresholds (Heavy-Duty Weather Seals):** - *Best For:* Main exterior entrances, villa doors, patio doors exposed to severe weather, typhoons, and wind-driven rain.
   - *Risk Level:* Low. Engineered with raised barriers, internal thermal breaks, and sloped drainage profiles to stop water infiltration dead in its tracks.

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### LESSONS FROM THE SHOWROOM FLOOR: A REAL-WORLD CASE STUDY

During a sudden torrential downpour accompanied by severe thunderstorm conditions, the drainage capacity outside our showroom became temporarily overloaded due to accumulated runoff and debris blockages. Because the showroom entrance was installed with a low threshold profile (approximately 2 cm in height), rainwater rapidly surpassed the threshold barrier, leaking directly into the interior showroom floor.

Our team had to manually scoop and mop water to prevent structural damage. While the showroom floor is constructed from water-resistant marble, consider the alternative:

> **What happens if your home features hardwood, laminate, or engineered timber flooring?**
> Water penetration over a low threshold will warp wood panels, breed toxic mold under subflooring, rot structural door framing, and lead to thousands of dollars in emergency restoration costs.

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### HOW TO CHOOSE THE RIGHT THRESHOLD FOR YOUR HOME OR PROJECT

When specifying exterior doors with your architect or contractor, follow these three rules to ensure long-term weatherproofing:

#### 1. Evaluate Ground Elevation and Slope
If the exterior ground level is equal to or higher than your indoor flooring level, water will naturally pool toward your doorway during heavy storms. Never install a low threshold in low-lying terrain without a high-capacity trench drain system.

#### 2. Factor in Local Climate and Exposure
If your geographic region experiences seasonal typhoons, hurricanes, or severe rainstorms, high weathered thresholds are mandatory. Exposed facades without wide roof overhangs demand elevated sill barriers.

#### 3. Match Threshold Material & Sealing Systems
High-performance exterior aluminum doors should feature thermal break thresholds paired with high-grade EPDM rubber gaskets, drip caps, and multi-point locking systems. A properly sealed high threshold ensures water tightness without compromising energy efficiency or structural insulation.

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### KEY TAKEAWAYS & BUYER CHECKLIST

 **Low thresholds look great, but offer minimal water protection during extreme rain.**
 **High thresholds provide superior weatherproofing, blocking wind-driven rain and floodwaters.**
 **Hardwood & parquet flooring require high thresholds to avoid costly water damage.**
 **Always consult door specialists to match threshold specs with site elevation and local climate.**

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### ABOUT WARREN WINDOWS & DOORS
Warren Windows & Doors is a premier manufacturer of high-performance aluminum window and door systems designed for residential and commercial architecture. Our product lineup includes passive house windows, thermal break aluminum doors, curtain walls, and storm-resistant patio door systems.