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. How to Diagnose & Evaluate Horizontal Foundation Cracks

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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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Horizontal crack high in masonry block wall (C) Daniel Friedman

These foundation damage assessment notes presume that you are examining a wall which is entirely or nearly all below-grade level.

Horizontal Foundation Cracks Located High on a Foundation Wall

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.

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.

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

Block foundation wall mid-wall crack damage (C) Daniel Friedman

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.

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

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.

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.

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:

Where are Horizontal Foundation Cracks Visible?

Frost and earth load cracking damage to a foundation wall (C) Daniel Friedman

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 draingage problems corrected for this structure to survive.

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

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 mroe 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.

Reader Question: Is this horizontal crack serious? Hairline horizontal crack evaluation request

Horizontal crack evaluation in masonry wall (C) InspectAPedia

My house is 20 years old and sits on a slope. I found a horizontal crack last weekend when I was out in the back yard. Normally I stay indoors and don’t go out to back yard.

I can’t say when the crack started. I think it is probably recent because the horizontal dark line is obvious. I start looking on internet. I love your website. A lot of info and very knowledgeable. Therefore I wonder if you can help giving some advices. I am scared right now.

Here are some details. The first picture was taken from the backyard. You can see the back of the house sits on a big wall of concrete. Actually, the whole house sits on concrete. The concrete thickness in the front of house is thin, and it gradually become thicker. The concrete wall is about 10 feet high in the back of the house as the picture shown.

There is a dark color horizontal crack. The dark color looks like caused by the moisture coming out of the crack. The crack starts from half way on one side of the house, runs across the back, and ends around the half way of the other side of house.

The second picture shows the close look of the crack. It is not big. I don’t know if it is hardline wide.

Could you please give me some opinions? I already scheduled visits with a few foundation repair companies. I hope you can provide me an independent assessment on how to fix it.


Horizontal wall crack closeup gives clues (C) InspectAPedia

A competent onsite inspection by an expert usually finds additional clues that would permit a more accurate, complete, and authoritative answer than we can give by email alone.

You will find additional depth and detail in articles at our website. And I'm in the dark about your comments about varyijng concrete thickness.

That said I offer these comments:

It's not clear if the cracked wall is reinforced poured concrete (lower risk) or a cement parge-coated concrete block foundation wall (higher risk). It's also not clear from the photo the extent of wall movement and bending - factors that along with rate of change, site conditions, and building construction methods would define the risks involved.

What I can see in your masonry wall crack photos includes:

A competent assessment requires an onsite inspection by an expert in foundation repair - perhaps an experienced mason or a structural or civil engineer who has specific experience with residential foundation wall troubleshooting and repairs.

An expert will look at the size, pattern, location, of the crack, the extent of wall bending (more than an inch is likely to be a more urgent concern), crack and movement history, site factors, and similar items in forming an opinion.

I realize that we don't want to waste an expert's time and our own money on an inspection and analysis that may not be necessary, and also that lots of "experts" find it safer for themselves to spend more of your money by calling for measures that may not really be appropraite.

In general, I would expet (OPINION) that an experienced building inspector, home inspector, or one of the foundation experts I listed above would, on seeing a wall like the one in your photos, figure that if the wall is close to perfectly vertical and there is no sign of rapid ongoing movement, a hairline crack is low enough risk that you could reasonably hold off on heroics and watch the wall and crack for signs of further movement.

It would make sense also to keep surface runoff and roof spillage (the downspout in your photo and the gutter above if it's clogged) away from the building foundation wall. It might make sense to include in your evaluation the condition of the brick veneer as well - as it looks as if water has run down the building wall.

Take a look at both

Reader Follow-Up: more details about the fine horizontal crack found in the wall photographed above

I finally found pictures from last year showing the horizontal line was already there.  So this is not new.  Yesterday two foundation repair companies came.  Both of them didn’t see anything wrong inside and outside.  There is no crack inside.  Floor is almost flat using test tool.  Drainage is ok.  Foundation is fine.  They can’t tell what was causing this horizontal crack line.  Both of them guessed this crack might be caused by cold pouring joint.  The hairline crack is a straight horizontal line starts from one side of the house, all across the back, and to the other side of house.  They offered a few tips to direct water away from the house.  They both told me nothing to worry about.  Just keep an eye on it.

They showed me that the concrete is parge coated.  I pointed out a spot to one of the inspectors.  It looks like some rust is leftover below a small parge coat crack.  You can see it in the picture.  He said that’s the spot of rebar.  He also showed me a few other spots which has rebars inside.

I feel ok now.  What should I do next?  Do I need to confirm this is really cold pour joint leak(which I don’t know how), or just keep an eye on it?

Sorry for confusing you about the thin/thick.  I should say the concrete retaining wall/foundation is shorter near the front of the house, and taller near the back of the house.

Reply: leaks into a concrete, brick, or block masonry wall can cause rust damage cracking or frost cracking

You confirm for sure that this is a poured concrete foundation wall.

Exfoliating rust damage at steel reinforcing mesh in brick veneer wall (C) Daniel Friedman

I noted earlier that your photo showed what looked like water stains on the exterior wall, also suggesting water was running down the wall.

If a building foundation wall is reinforced poured concrete and if water was leaking into the wall, I noted in my earlier message that water running down a masonry wall where re-bar or reinforcing steel mesh is close to the wall surface or where cracks (say shrinkage cracks or others) admit water into the wall, rust can cause further wall cracking as the pressure exerted by exfoliating rust along steel reinforcement is quite powerful.

This rust damage pattern in foundation walls is more common in brick or block structures (such as shown in our photo at left).

I also note that because steel mesh or re-bar placed in a masonry wall structure are rather straight, water and thus rust damage to the wall, if caused by water intrusion where steel reinforcement has been wet from leaks on or into the wall, tends to cause cracking that is rather straight-line.

Frost cracking that follows water leaks into a masonry wall is more likely to be horizontal in a block or brick wall but might be horizontal in a poured concrete wall if water is entering at a crack where steel reinforcement is close to the wall surface.

Concrete parge coating may have been added to cover up prior rust or water damage to the foundation wall

It is common to see concrete parging coating a concrete block foundation wall. It is less common to see concrete parge coating on the exterior of a poured concrete wall. One might speculate that if found the parging may have been added on a conctrete wall it might have been done by a prior owner for cosmetic reasons, to cover spalling or rust-caused cracking in the wall surface.

If the prior owners did not realize that wall damage was being caused by roof runoff spilling down the wall surface, even though the wall was parge-coated to cover up old damage that same problem might be expected to recur.

Your onsite inspectors confirmed (by implication in your message not by explicit remark) that there is no significant movement in your wall - leaning, bending, bowing, etc.  That in turn means you're not facing an urgent costly structural repair.

  1. Fix the causes of roof gutter overflow/spillage that sends roof runoff water down the wall (suggested by your first photo)
  2. Cosmetic repairs to the parging would be fine and might help keep water out of the crack. Any "patch" type repair such as using masonry caulk or even concrete patch will look just like that - like a patch. To not see the repair at all you'd need to either patch and then paint the wall surface (which means re-painting from time to time in the future) or re-parge-coat the wall anew - a more costly alternative.

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.

Watch out: To be used properly, this information must be combined with specific on-site observations at the particular building in order to form a reliable opinion about the condition of that building's foundation. Anyone having concern regarding the structural stability, safety, or damage of a building, foundation or other components, should consult a qualified expert.

Foundation Movement Articles


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