How Do You Fix Cracks In Clay?

Table of Contents

Introduction

Clay soil is notorious for cracking, which can cause extensive damage to foundations, walls, and landscaping. While clay’s tendency to expand and contract with changing moisture levels makes cracks inevitable in some cases, there are ways to repair cracks to prevent further damage. With proper assessment, preparation, repair techniques, and preventative measures, many common cracks in clay can be fixed successfully and cost-effectively. This guide covers the causes of clay cracking, steps for repairing cracks, methods for preventing future cracks, and when you may need to enlist a professional. With some effort and diligence, you can restore structural integrity, curb appeal, and value to your clay-based property.

Causes of Cracks in Clay

Clay soils are prone to cracking due to their ability to expand when wet and shrink when dry. Here are some of the most common causes of cracks in clay:

Shrink/Swell Cycles – As clay absorbs water, it expands. When it dries out, it shrinks. This repetitive cycle of shrinking and swelling can cause cracks over time.

Tree Roots – Tree roots grow and expand underground, exerting upward pressure on clay soil. This can cause cracks as the clay heaves upward.

Poor Drainage – Poor drainage leads to excessive moisture in clay soil, resulting in expansion and subsequent cracking as it dries.

Settling – If the clay under a foundation or slab settles unevenly, it can cause cracks due to shifting support.

Freezing Temperatures – In cold weather, water in clay can freeze and expand, leading to frost heave. This upward pressure results in cracks when thawing occurs.

Construction Activity – Excavation, drainage issues, vibration from machinery, and changes to the landscape can disturb clay and cause subsidence cracking.

Assess the Damage

Before attempting any repairs, it’s important to fully assess the cracks to understand the extent of the problem. Examine each crack closely and look for the following:

Width of the cracks – Measure the widest part of each crack in millimeters. Hairline cracks less than 1mm wide may not need repair. Cracks wider than 3mm often require more extensive work.
Depth of the cracks – Use a wire to probe the depth and determine if the foundation has shifted. Surface cracks are simpler to repair than deep foundation cracks.
Location of cracks – Note where the cracks originate and end. Cracks near windows, doors, and corners often indicate settling, while cracks in the center can mean upward movement.
Pattern of cracks – Straight horizontal or vertical cracks typically arise from minor causes like poor soil hydration or small foundation movements. Jagged, branching cracks suggest serious issues like an unstable foundation or expansive soils.

Checking for plumb lines and level floors will also reveal if any shifting has occurred. Document the cracks with photos and measurements to monitor any changes over time.

Prepare the Area

Proper preparation is key to repairing cracks in clay effectively. Here are the steps to take:

Clean out any debris, dirt or loose material from the cracks using a wire brush, compressed air or vacuum. You want the inside of the cracks to be clean so the repair material can bond properly.
Widen and deepen the cracks if they are hairline or shallow, using a chisel and hammer. The repair material needs something to grab onto along the sides of the crack.
Bevel the edges of the cracks at a 45 degree angle using a chisel or grinder to help lock in the repair.
Remove any loose or crumbling surface material around the cracks to expose fresh, solid clay.
Wash the cracks out with water to remove dust and allow to fully dry before repairing.

Properly widening, cleaning and drying the cracks will help the repair material fully fill in and bond with the clay for long-lasting repairs.

Fill the Cracks

Once you’ve prepared the area by cleaning out the cracks, it’s time to fill them. There are several options for filling cracks in clay:

Patching compounds – These are specifically designed for repairing cracks and come in caulk tubes or larger buckets. Look for patching compounds made for masonry.
Hydraulic cement – This type of cement sets quickly by chemical reaction with water. It will bind strongly to clay. Mix it with water to create a paste to fill cracks.
Bentonite – This swelling clay material will expand when wet to fill cracks. It comes in powder form, so mix it with water before applying.

Use a palette knife, putty knife or trowel to force the filler material into the crack, pressing firmly to ensure it penetrates fully. Apply slightly more than needed and let the excess remain on the surface until dry. Once dry, sand or scrape the surface smooth and level with the surrounding clay.

Reinforce and Stabilize

Once the crack is filled, you’ll want to add reinforcements to strengthen the area and help prevent future cracking. Here are some tips for stabilizing clay after a crack repair:

Install root barriers like copper mesh or polyethylene sheeting near the foundation. This will prevent tree roots from causing cracks in the future.
Add drainage with perforated pipe along the foundation perimeter. Proper drainage prevents water buildup and hydraulic pressure that can crack clay.
Use helical anchors or pier supports to stabilize the area and provide more support. Anchors can be installed without heavy equipment.
Steel rebar pins can be driven into the clay to reinforce the soil mass. Connect rebar with wire to create a reinforcing grid.
Apply a fiber reinforcement mesh over the crack repair and embed it into thin layers of fresh stucco or mortar.

Stabilizing and reinforcing the area after filling the crack will help prevent cracks from reappearing. This provides long-term structural support.

Protect Against Future Cracks

After repairing existing cracks, it’s important to take preventative measures to protect your clay against future cracking. Here are some tips:

Regular Maintenance

Check the area routinely for new cracks or movement. Small cracks are easier to repair before they expand. Remove any vegetation growing in cracks. Keep gutters and drainage areas clear of debris to prevent water damage.

Improve Drainage

Make sure water flows away from the foundation. Grade soil so it slopes at least 6 inches over 10 feet. Use downspout extensions to direct rainwater away from the house. Install French drains if needed.

Control Vegetation

Keep trees and shrubs trimmed back from the foundation. Their roots can cause clay to swell and shrink. Avoid planting trees with invasive root systems near the foundation.

Stabilize Soil

Adding organic material like compost can help stabilize swelling clays. A soil injection system pumps stabilizing chemicals into the ground. Reinforce soil with geogrids or geo-textiles.

With diligent maintenance and moisture control, you can help prevent cracks from returning and protect your clay foundation.

Hire a Professional

Cracks in clay can sometimes be symptoms of major foundation problems that require professional repair. Here are some signs it’s time to call a foundation repair company:

Cracks wider than 1/4 inch – These large cracks likely indicate significant shifting or settling.
Cracks that rapidly reappear after filling – This points to an underlying problem that needs addressing.
Steps or gaps between floors or ceilings – This shows major structural movement.
Doors or windows out of alignment – Foundation issues are pushing the structure out of shape.
Cracks accompanied by sticking doors or windows – The house frame is distorted.
Multiple cracks throughout interior and exterior walls – Extensive cracking requires an expert evaluation.
Cracks coupled with leaks or damp areas – Water penetration can worsen foundation damage.

For any of these signs, consult a reputable foundation repair company to inspect, diagnose, and provide long-term solutions. They have specialized techniques and equipment to stabilize the foundation and prevent future cracking.

Cost of Repairing Clay Cracks

Repairing cracks in clay can range significantly in cost depending on the severity of the damage and whether you tackle it as a DIY project or hire a professional. For minor cracks, a DIY approach may only cost $20-50 for materials. However, for serious structural cracks, hiring a foundation repair company could cost $300-500 per crack or more for assessment and repair.

Here’s a breakdown of typical costs:

DIY minor crack repairs – $20-50 for hydraulic cement, epoxy fillers, etc.
DIY major crack repairs – $100-300 for materials such as anchors, stabilization mesh, gravel backfill, etc.
Professional assessment – $100-300 per crack
Professional minor crack repair – $300-500 per crack
Professional major crack repair – $500+ per crack

Keep in mind with DIY repairs there is a risk of not properly identifying and addressing the root cause. Hiring a professional for an assessment can save money in the long run by preventing ongoing issues. For expensive foundation repairs, getting multiple quotes is advised.

Conclusion

Repairing cracks in clay can seem daunting, but is doable as a DIY project if you take the proper steps. The keys are assessing the damage to determine the cause, cleaning and preparing the area thoroughly, using flexible fillers and sealants made for clay specifically, and reinforcing or stabilizing the area to prevent future cracking. Pay attention to proper curing times and application instructions for products. Monitor repaired cracks over time and maintain seals. Severe structural issues are best left to professionals. With some persistence and patience, you can repair clay cracks and restore the integrity of your walls or surfaces.

A few tips to remember:

Prevention is ideal – maintain proper moisture levels in clay through drainage and landscaping.
Repairs are often temporary fixes – monitor and maintain them regularly.
Thorough surface preparation is key for good adhesion and effective repairs.
Use the right materials for the job – flexible epoxies and polyurethanes made for clay.
Reinforce repairs with mesh, rebar, anchors, or brackets as needed.
Hire a structural engineer for assessing major foundation or load-bearing wall cracks.

With some diligence and care, you can repair cracks in clay and restore your surfaces. Just take it step-by-step.