Concrete honeycomb in the exterior face of your concrete slab is a result of the cement mixture to improperly fill the voids and cavities created by the coarse grained aggregate. The use of the term is derived from the appearance of the slab because it resembles the honeycomb nests created by honey bees.
Concrete Honeycombing Causes
Concrete honeycombing is usually caused by a few common factors, including:
- A lack of integrity at the perimeter form boards at the time the concrete is being poured.
- Improper cement to water ratio that causes poor workability
- Poor consolidation practices or inefficient means of vibration
- Improper reinforcing bar placement at vertical and horizontal grade beam transitions; leads to poor concrete fill.
- Over-sized aggregate or poor sampling
Is Concrete Honeycombing a Concern?
For the purposes of a home inspection, honeycombing is mostly a cosmetic condition that is found only upon the exterior face of the home’s foundation. By and large, honeycombing is left untreated with limited to no adverse affects upon the performance of your foundation. However, depending on the specific location of the honeycombing, it could indicate a more deleterious condition. For instance, if the honeycombing was deep enough to allow moisture into the cavities that house reinforcement or post-tensioned cable anchors, corrosion could weaken the performance of the foundation. Anytime the structural components of your home’s foundation is being damaged corrective measures should be undertaken. In other situations the affected area may extend itself deeper into the mass of the concrete, in which case the only way to confirm the condition and treat it would be by way of a structural engineer. This is a not-too-common condition and unless specifically addressed during a home inspection or specific evaluation, should not be added to your list of concerns.
Concrete Honeycomb Repair
Assuming that your condition is isolated to the exterior face of your foundation a relatively minor repair can be undertaken. The repair itself consists of a few basic steps, but should nonetheless be undertaken by someone that is competent and knowledgeable about the procedure. Common approach includes:
- Isolate the affected area by removing layers of honeycombing until suitable concrete is exposed
- Thoroughly clean the area to be repaired and remove all dirt and loose aggregate
- Wet the cleaned area prior to applying non-shrink grout
- Texture and color should then be matched for aesthetic finish