Concrete Honeycomb In Residential Foundations

My clients frequently express concerns about the concrete honeycomb texture that they see on the exterior face of their foundation slab. Of course, their concern is that the presence of honeycombing in the foundation is a structural concern.

In this brief post, I’m going to shed some light on;

1. The origin of concrete “honeycombing” and what causes it
2. Potential effects on your home as a result of honeycombing
3. Common repairs & treatments for concrete honeycombing

Concrete Honeycombing Definition and Causes

The term honeycombing was used in concrete construction to describe the course and rocky appearance on the outer foundation because of its close resemblance to honeycomb nests built by honey bees.

There are many common causes of concrete honeycombing, including;

• Imbalances in the fine material added, allowing larger aggregate (rocks) to consolidate
• Poor cement to water ratio, which can reduce the concretes workability
• Inefficient means of vibration directly after the concrete is poured
• Improper reinforcing bar placement at vertical and horizontal grade beam transitions leading to poor concrete fill
• Adhesion or leakage of concrete at poorly braced form boards
• Low-quality or damaged form boards, which prevents firm contact with the concrete

Is Concrete Honeycombing a Concern?

Honeycombing is mostly a cosmetic condition, and I have yet to encounter a foundation that was showing any signs of adverse performance.

The only time I’ve seen concrete honeycombing be a concern, depending on the specific location of the honeycombing, is when the honeycombing was deep enough to expose the steel reinforcements (rebar) or post-tensioned cable ends. When the steel is exposed on the perimeter of the concrete due to deep concrete honeycombing, corrosion will weaken the steel over time, causing additional spalling and durability loss to the structure.

Concrete Honeycomb Repair Tips

There are two primary ways to repair concrete honeycombing, which will help to cosmetically improve the outer surface of your home’s foundation. In my own home, I chose to apply an acid stain. I had some mild honeycombing on the front of my exposed foundation, and I wanted to blend my exposed foundation wall with the landscaping. I set aside a day and used three 1 gallon cans of stain with a 2-gallon sprayer that I picked up from Amazon.

Another option is to treat the concrete honeycombing by way of a high-strength, non-shrink grout.

If the honeycombing is deep or if the foundation reinforcements are exposed, this is the best option. You’ll want to follow the specific directions provided by the manufacturer, but the basic steps include:

• Isolate the affected area by removing chipping or flaky layers of honeycombing until the suitable concrete is exposed
• Thoroughly clean the area to be repaired and remove all dirt and any loose aggregate
• Wet the cleaned area before applying the high strength, non-shrink grout
• Texture/color should then be matched for aesthetic finish

I hope you enjoyed this blog post. I’ll do my best to keep things updated should new or more beneficial information comes available. Feel free to share, comment, or otherwise engage with me should you have any questions.

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