Waterproofing a Rubble Stone Foundation: Homeowners Guide
For professionals in the business of basement waterproofing in Brooklyn, Queens, and Long Island, New York—as I have been for the past 25 years—rubble stone foundations present numerous challenges. Commonly referred to as old stone foundations, river stone foundations, or field stone foundations, these terms are often used interchangeably to describe rubble stone foundations. While there are various types of stone foundations distinguished by the type or size of the stones used, this article encompasses all types and sizes of stone foundations. To simplify, I will use the terms “Rubble Stone Foundation” and “Stone Foundation” interchangeably throughout this article, as “rubble stone” is the most commonly recognized term.
This article focuses primarily on the challenges of repairing rubble stone foundations, in particular, waterproofing rubble stone foundations. However, it will also briefly touch on the complexities of structural work on these foundations. If you’re interested in understanding the intricacies of structural repairs for rubble stone foundations, I encourage you to contact Zavza Seal LLC for expert advice.
Waterproofing Rubble Stone Foundation
The era of stone foundation installation has largely passed. To my knowledge, no construction companies in Brooklyn, Queens, or Long Island, New York actively install stone foundations for houses or buildings today. Poured concrete foundations have become the industry standard due to their superior durability, ease of waterproofing, and overall efficiency. Cinder block foundations, known for their cost-effectiveness, are the second most common choice.
There are several reasons why stone foundations have become a relic of the past, which I will discuss in this article. The primary reasons include the labor-intensive nature and high cost of installation, as well as the inherent difficulty in waterproofing these foundations. Unlike modern materials, stone foundations lack the cohesive, straight surfaces required for effective waterproofing using membranes or liquid rubber.
Rubble Stone Construction: Composition and Challenges
A rubble stone foundation is made up of loose stones bonded together with mortar. While modern mortar materials have improved substantially over the years, it is likely that the mortar used in the construction of your home’s rubble stone foundation is inferior to today’s advanced products.
These foundations primarily consist of two components:
- Stones: Rubble stone foundations were traditionally built using materials like limestone, river stone, or field stone. The strength of these stones is measured in pounds per square inch (PSI), which is significantly higher compared to cinder block or poured concrete foundations. While cinder block foundations typically have a strength of 3,000–3,500 PSI and poured concrete foundations range from 3,500–4,500 PSI, the stones used in rubble stone foundations can range from 6,000 to 20,000 PSI. Additionally, stones are non-porous and naturally resistant to water, meaning they are not the cause of water-related issues in basements.
- Mortar: The mortar, which binds the stones together, often deteriorates over time—especially in foundations constructed over a century ago, many of which predate World War I. Water penetration in these foundations is primarily due to the weakened and compromised mortar.
Structural Characteristics of Rubble Stone Construction
The footing of a rubble stone foundation is typically created by placing larger stones at the base of the foundation. Unlike modern foundations, this method does not provide a cohesive or continuous footing, making it difficult to waterproof effectively.
The Problem with Rubble Stone Construction
The primary challenge with waterproofing a rubble stone foundation lies in the lack of a continuous and solid footing. A fractured base makes it significantly harder to apply waterproofing solutions. Additionally, the absence of a cohesive foundation wall surface creates further obstacles in preventing water penetration. Unfortunately, these challenges do not have easy solutions.
The Solution to Waterproofing Rubble Stone Foundations
The most effective solution for waterproofing a rubble stone foundation—or any foundation—is to excavate the exterior perimeter of the problem area and waterproof it from the outside. This approach addresses the root cause of water intrusion and ensures a more permanent fix.
