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Photograph of a bowed concrete block foundation wall, probably from frost cracking. Drop a plumb line to measure total inwards bulging of this block foundation wall. Horizontal Foundation Cracks

Diagnose cause, severity, collapse risk

Horizontal masonry wall or foundation cracks:

How to recognize, evaluate, diagnose & repair horizontal foundation cracks and signs of foundation damage.

Foundation cracks and movement are discussed by type and location of foundation cracks, vertical foundation cracks, horizontal cracks, and diagonal foundation cracks, and shrinkage cracking.

Foundation cracks, which are signs of foundation damage, can mean very different things depending on the material from which a foundation is made, the location, size, and shape of the foundation crack, and other site observations.

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- Daniel Friedman, Publisher/Editor/Author - See WHO ARE WE?

Causes & Effects of Horizontal Cracks in Foundation Walls

These foundation damage assessment notes presume that you are examining a wall which is entirely or nearly all below-grade level. We describe the common causes of cracks that appear high, in the middle, or lower in the foundation wall.

Watch out: severely buckled foundation walls, particularly those constructed of unreinforced concrete block, brick, or stone, are at risk of collapse.

Such collapses can occur suddenly and precipitously even when the foundation crack or damage has been visible for some time. The result can be a dangerous building collapse causing property loss, injury, even death.

Article Contents

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How Severe is a Horizontal Crack in a Foundation Wall

Severely buckled foundation wall seen from the crawl space (C) InspectApecia.com lash

Opinions vary about just how serious various extents of foundation lean or bulge really are, and the actual risk of collapse depends on additional site conditions such as building, size, shape, impact on structure, separation of building structural conditions, signs of ongoing or recurrent movement, and other factors.

At a conference organized by the author on foundation crack evaluation, expert engineers and architects among the attendees generally agreed that if there is an inwards bulge (or lean) in a block wall or brick wall of one inch or more, the movement is serious and needs expert attention.

Also see FOUNDATION BULGE or LEAN MEASUREMENTS which explains a simple method for determining how much bulge or lean is present in a foundation or wall

then see FOUNDATION MOVEMENT ACTIVE vs. STATIC which helps determine if the foundation movement is ongoing,

and see FOUNDATION DAMAGE SEVERITY for a discussion of just how much foundation movement is likely to be a concern.

Readers should also see our article series at CONCRETE SLAB CRACK EVALUATION since those pages also assist in distinguishing among types of cracking in concrete.

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Horizontal Foundation Cracks Located High on a Foundation Wall

Horizontal crack high in masonry block wall © Daniel Friedman at InspectApedia.com

Horizontal foundation cracks located in the upper third of a concrete block wall (presuming most of the wall is below grade) are most likely to have been caused by vehicle loading or in freezing climates, by surface and subsurface water combined with frost.

In northern climates if we see cracked mortar joints in the top third of a block wall, at about the same depth as the frost line in that area the damage is almost certainly due to frost.

Often outside we'll find corroborating evidence such as drip lines below the building eaves confirming a history of roof spillage against the building, and back inside we may see that the foundation damage is occurring only at the building walls below roof eaves and not at the gable ends of the home.

  • Cold climates- frost, possible displacement inwards
  • Possible vehicle loading, displacement inwards

Our photo (left0 illustrates an example of this foundation wall crack pattern: the masonry block foundation wall shows open horizontal cracking in the second mortar joint from the wall top.

To further understand this crack, it would be useful to notice outside just where the backfill soil height is with respect to the wall top.

Typically when we see a crack high in the wall like in this photo its cause is one of the bulleted items listed just above: frost loading or vehicle loading.

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Horizontal Foundation Cracks Located at Mid-wall Height on a Foundation

Block foundation wall mid-wall crack damage © Daniel Friedman at InspectApedia.com

Masonry block or stone walls which are cracked and/or bulging inwards at mid height on the wall are likely to have been damaged by vehicle traffic or earth loading.

  • Possible vehicle loading

     (look for a driveway near the wall or site history involving movement of heavy equipment near the wall)
  • Backfill damage -

    excessive height or premature backfill before the first floor framing was in place.
  • Hillsides -

    earth loading or earth loading exacerbated by water or frost
  • Areas of wet soils -

    likely to be earth-loading or earth loading exacerbated by water or frost

Our block wall horizontal crack photo just above shows these conditions.

Provided that an outside inspection confirms that the soil backfill height is close to the top of this foundation wall, finding horizontal cracking in the middle third of the wall, below the frost line for the area in which this building is constructed, argues that the crack is not caused by frost or freeze damage but more likely is caused by earth loading exacerbated by the added weight of wet soils or possibly those conditions combined with vehicle loading.

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Horizontal Foundation Cracks Located Low on a Foundation Wall

The forces exerted by soils against a foundation wall increase geometrically as we move from surface level of the soil against the wall to the areas near the bottom of the wall. In other words, earth pressure is greatest at the bottom of the wall.

This fact helps us distinguish between frost or water-related cracking and simple earth loading in some cases since a wall which has become dislocated laterally only at or near its bottom is likely to have been damaged by earth loading.

  • Earth Loading, especially if in an area of dense or wet soils - the total force of soil pressure against a foundation wall increases as we move down from the soil surface towards the bottom of the wall and its footing.
  • Horizontal dislocation of a masonry block or brick wall may appear first as a crack and then later as horizontal movement as a wall is pushed inwards by earth or wet soil pressure.

Where a floor slab helps hold the wall footing in place against horizontal movement, earth loading pressures against the foundation wall are more likely to cause inwards movement and cracking in the mortar joints above the floor slab.

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Causes of Horizontal Cracks in an Attached Garage Foundation

Construction methods for attached garages (as opposed to a garage located under a home and adjoining its basement) may create some special opportunities for foundation cracks:

  • Shallow garage footings:

    The garage foundation footings are less deep than the house footings, exposing the foundation to other risks of frost or settlement damage and movement.
  • Garage additions:

    The garage may have been added after original construction, creating newly-disturbed soils around the foundation and footings that have settled more recently than that of the original home.
  • Garage slab settlement and cracking:

    A garage foundation is often constructed as a concrete footing and a low masonry block wall, followed by dumping fill inside this structure to raise the level of the garage slab to the desired height.

    A common construction error is the omission of adequate soil compacting before the garage slab is poured. A related common construction shortcut for these "raised slabs" (on fill, higher than and not resting on the garage wall foundation footings), is the omission of pins connecting the slab to the garage foundation wall at its elevated position.

    The result of these details is that as the soils below the slab settle and compact the slab can move and settle significantly. Depending on the amount of garage floor slab reinforcement (wire or re-bar or none), the slab may crack as well as tip and settle.

    How does garage slab settlement crack the garage foundation walls? The weight of a garage floor slab, combined with the weight of vehicles in the garage, compresses the soil below the slab.

    Soil pressure includes an outwards force which can cause horizontal cracks in a masonry block garage foundation wall. Look for these cracks outside the garage and above grade-level.
  • Detecting soil voids below a garage slab

     is quite possible using this "ghost busters" technique: drag a heavy chain across the floor and listen to the sound it produces.

    If the chain moves across an area of soil void you'll hear a change in pitch in its sound, typically dropping lower.

    This is not a technique for every building inspection but it is useful when evaluating garage floor slab movement, tipping, cracking, or foundation cracks.

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Where are Horizontal Foundation Cracks Visible?

Frost and earth load cracking damage to a foundation wall © Daniel Friedman at InspectApedia.com

Horizontal foundation cracks are usually visible only from inside a basement or crawl area unless building is all masonry.

Occasionally horizontal cracks may be visible above-grade on a building exterior or interior wall, as we illustrated in our repair advice field report described below.

Lateral or horizontal movement of a masonry foundation wall inwards from earth pressure will often be seen at the first mortar joint above a basement or crawl space slab. Remember that the slab itself may be holding the very first course of masonry blocks or brick in place.

This is a useful detail to keep in mind if you are using a plumb line and measuring tape to document the total amount and location of wall movement.

The bottom course of concrete blocks or bricks, held in place by the floor slab, can usually be taken as a baseline of zero movement, from which other measurements to the plumb line are compared over the height of the wall.

Our photo (left) illustrates severe bulging damage to a concrete block foundation wall where a combination of water, frost, and earth loading are collapsing the foundation wall. The "jackleg" repair attempt shown by multiple diagonal braced 2x lumber is at best a stop-gap measure.

The wall will need to be rebuilt and the outside water and drainage problems corrected for this structure to survive.

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Horizontal Masonry Wall Crack Cause, Diagnosis, & Repair Advice

Horizontal cracks in reinforced brick or concrete block walls and in poured concrete walls can occur because of

  • Wall movement

    such as bending or loading (footing settlement, tipping, leaning, frost pressure, earth pressure, etc.)

    See HORIZONTAL MOVEMENT IN FOUNDATIONS
  • Exfoliating rust pressure

    from rust caused by water leaks into the wall structure, particularly where steel mesh or re-bar are close to the wall surface or are for other reasons exposed to water leaking into the wall. We also find this rust damage to masonry walls of all types at steel lintels over windows and doors

    Also see BRICK FOUNDATIONS & WALLS
    and

    Also see BRICK STRUCTURAL WALLS LOOSE, BULGED
  • Shrinkage cracks

    - may run in any direction, including roughly horizontal, but tend to be discontinuous and not straight, and tend to occur more at natural points of variation in stresses in the concrete wall (or floor) such as at penetrations or changes in wall height, width, thickness, etc.

    See SHRINKAGE CRACKS in CONCRETE

Watch out: while many horizontal cracks are of only cosmetic significance, others may be a source of leaks (and further damage) into the wall or water intrusion into the building, and more seriously, significant horizontal cracks diagnosed as caused by wall buckling or bending or movement are likely to require structural repair or reinforcement, or in extreme cases like that shown in our page to photograph of a buckling masonry block wall, foundation wall reconstruction.

 

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Continue reading at HORIZONTAL MOVEMENT IN FOUNDATIONS or select a topic from the closely-related articles below, or see the complete ARTICLE INDEX.

Or see HORIZONTAL FOUNDATION CRACK SEVERITY FAQs - examples of horizontal foundation wall cracks & questions & answers about that damage, posted originally on this page.

Or see these

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HORIZONTAL FOUNDATION CRACKS at InspectApedia.com - online encyclopedia of building & environmental inspection, testing, diagnosis, repair, & problem prevention advice.


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