How To Look At A House

McGarry and Madsen's home inspection blog for buyers of  

site-built, mobile/manfuactured and modular homes

There's cracks running along the home's concrete tie beam. What's wrong?

Wednesday, July 11, 2018

You likely have concrete “spalling,” which is caused by moisture penetrating the layer of concrete covering the reinforcing steel in the beam, column, or foundation pier. Over time, the steel begins to rust inside the beam and, because rust is slow but very powerful expansive process, cracks appear at the surface over the reinforcing steel.

     It‘s a progressive deterioration, because the open crack allows more moisture to accelerate the corrosion--formally known as ferrous oxide scale--which opens the crack further. Eventually small chunks of concrete begin falling out and, if left without repair long enough, structural failure follows.  


  Spalling is more prevalent along the coast, where a salt mist gets blown over the surface of the beam from the ocean breeze. It starts appearing in oceanfront homes in Cedar Key as early as 20-years after construction, but occurs eventually at inland homes--just much later.

   Any exposed area of steel-reinforced concrete can develop spalling, including floor slabs and precast components like window sills (example shown below).

  Oceanfront exposure is actually only one factor that allows spalling to begin. Too little concrete coverage over the steel (less than about one-and-a-half inches), poorly placed concrete with air pockets in it, and an upset of the natural alkalinity of the concrete can all set spalling in motion. In the photo below, corrosion of reinforcing steel that has been set too close to the bottom of a concrete second floor walkway has started to pop off chunks of concrete below it. The cantilevered slab has temporary supports in place while it awaits repair, because of the loss of structural integrity.

   Even a concrete slab on the ground can develop spalling if the steel mesh is pulled up too close to the surface, as in the photo below. 

  The fix is simple but labor-intensive: each crack line has to be jack-hammered open to expose the surfaces of the steel reinforcing bars. The rust is then cleaned away with a chemical solution like Ospho®, shown below, and stiff brush, coated with an anti-corrosion solution, and then a special concrete/mortar mixture is packed into the damaged area and smoothed out along the surface. 

    Also, see our blog post What would cause long horizontal lines of brick mortar to fall out?

• • • • • • • • • • • • • • • • • • • • • • • • • • • • 

To learn more about exterior walls and structures, see these other blog posts:

What is the average lifespan of a house foundation?

What causes vertical cracks in fiber cement siding planks?

What causes raised white lines of residue on a block wall that are crusty and crumbling? 

What is the difference between soil subsidence, heave, creep, and settlement? 

How much ventilation is required for the under-floor crawl space of a home? 

How can I tell if a diagonal crack in drywall at the corner of a window or door indicates a structural problem?

What causes the surface of old bricks to erode away into sandy powder? 

What are the pros and cons of concrete block versus wood frame construction?

Should I buy a house with a crawl space? 

Why is my stucco cracking?

How do I recognize serious structural problems in a house?

 What causes stair-step cracks in a block or brick wall?

What causes a horizontal crack in a block or brick wall? 

What is engineered wood siding?

Should I buy a house that has had foundation repair? 

What is a "continuous load path”?

Should I buy a house with asbestos siding?   

How can I tell if cracks in the garage floor are a problem or not? 

What do you look for when inspecting vinyl siding?

Why is housewrap installed on exterior walls under the siding? 

How do I recognize serious structural problems in a house?

Why did so many concrete block homes collapse in Mexico Beach during Hurricane Michael? 

How can I tell if the concrete block walls of my house have vertical steel and concrete reinforcement?

Should I buy a house with structural problems? 

What are those powdery white areas on my brick walls?

What causes cracks in the walls and floors of a house?

How can I tell if the exterior walls of a house are concrete block (CBS) or wood or brick?

What are the common problems of different types of house foundations? 

• What are the warning signs of a dangerous deck?

How can I tell whether my house foundation problems are caused by a sinkhole or expansive clay soil?

        Visit our EXTERIOR WALLS AND STRUCTURE page for other related blog posts on this subject, or go to the INDEX for a complete listing of all our articles.

Water Heaters

Water Heater Age

"What Are The

Signs Of..."

Septic Tank Systems

Structure and Rooms

Plumbing Pipes

Termites, Wood Rot

& Pests

Sinkholes

Stairs

When It First

Became Code

"Should I Buy A..."

Park Model Homes

Site

Shingle Roofs

Safety

Stucco

Remodeling

Wind Mitigation

Roof and Attic

"Does A Home

Inspector...?"

Pool and Spa

"What Is The Difference Between..."

Radon

Brick

Plumbing

Concrete and

Concrete Block

Metal Roofs

Foundations

Modular Homes

Rain Gutters

Mold, Lead & Other Contaminants

Condominiums

Older and

Historic Houses

Crawl Spaces

Mobile-Manufactured Homes

Building Permits

Life Expectancy

Clay Soil

Insurance

Floors

Insulation

Toilets

Exterior Walls

& Structures

Generators

Common Problems

HUD-Code for

Mobile Homes

Garages and Carports

Flat (Low Slope) Roofs

Electrical Panels

Sprinkler Systems

Electrical Receptacle Outlets

4-Point Inspections

Hurricane Resistance

Frequently Asked Questions (FAQ)

Home Inspection

Heating and Air Conditioning

Building Codes

Fireplaces and Chimneys

Inspector Licensing

& Standards

Energy Efficiency

Washers and Dryers

Electrical

Kitchens

Doors and Windows

(placeholder)

Cracks

Electrical Wiring

Click Below  

for Links

to Collections

of Blog Posts

by Subject

Plumbing Drains

and Traps

Appliances

Smoke & CO Alarms

Aging in Place

Top 5 results given instantly.

Click on magnifying glass

for all search results.

Bathrooms

Lighting

AFCI, CAFCI,

DFCI, & GFCI

Sinks

Air Conditioner & Furnace Age/Size

Attics

Electrical Switches

Siding

Search

This

Site

Water Intrusion

Electrical - Old

and Obsolete

(placeholder)

Foundation Certifications

Tiny Houses

About Us

(placeholder)

Wells