1510
ENGINEERING

What if your foundation crack has water seeping through, but it’s just a tiny bit, and it doesn’t really bother you? Do you really need to fix it? If it were my house, I would fix it. If your foundation does have steel reinforcement, the water will corrode that steel as it runs through the crack. You also risk the tiny seep of water increasing in volume during a particularly wet season.

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If you have a problematic crack, it’s difficult to say exactly what the fix is without evaluating your house. Typically, I recommend correcting all grading around the house so water runs away from the foundation, fixing all gutters and downspouts to direct water away, and then epoxy injection into the crack to stabilize it. Again, it depends on your specific situation. If you have soft or expansive soils, you might also need to stabilize the foundation with helical piers or various other stabilization methods. I'm happy to come take a look at your problematic foundation crack - Contact Us or you can book an appointment directly, click Book Online.

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Cracks in a Concrete Floor or Garage Floor

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As we reviewed in the last section, concrete is almost sure to crack due to drying shrinkage, and this effect is even more pronounced in concrete slabs, so much so that we add crack control joints to try to control the crack locations. A crack control joint is a groove, tooled in while the concrete is soft or cut with a saw a few days after the pour. The concrete slab is thinner and therefore weaker at the crack control joint, and so it should crack there. If we didn’t use crack control joints, the slab would crack along jagged alignments in random locations, an unsightly cosmetic issue that we seek to avoid. Concrete doesn’t always crack along the crack control joints, especially if the slab doesn’t have a uniform thickness, or has points where the drying shrinkage stress is concentrated, like outer corners, posts, plumbing terminations, etc. 

As long as the concrete slab stays flat across a crack, the crack is cosmetic and not a structural issue. If you have poor subgrade soils and the slab is heaving or settling across the shrinkage drying crack, then that is a serviceability concern and may need to be addressed. Serviceability means the slab is not meeting all its service criteria- in this case, it’s no longer providing a flat floor. A serviceability issue is not necessarily a structural issue, but may still need to be corrected if the owner chooses to do so. Minor settling or heaving that results in a serviceability issue can be easily corrected by injecting grout or foam beneath the slab to restore the slab's flatness. 

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If the concrete slab has cracks resulting from significant subsidence or heaving, I would consider that a structural issue, as it indicates serious subgrade movement. A qualified professional can differentiate between shrinkage drying cracks and cracks due to subsidence or heave, but in general, cracks due to subsidence or heave will originate around the area with the most movement and branch out. Because they result from serious subgrade movement, grout or foam injection isn’t a viable repair method for these slabs. A proper repair will usually involve partial or complete removal of the slab, assessment of the subgrade soils, remediation of the subgrade soils through drainage or other means, and then repouring the affected slab areas. If you've got a crack in your concrete slab and want an engineer to take a closer look, you can book an appointment directly, click Book Online.

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Cracks in a wall

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Most homes in Colorado, I would guess probably greater than 95 percent, are wood-framed structures, so I’ll address interior cracks in a wall with the assumption that the house is conventional light framing. With a conventionally framed house, the cause of drywall and plaster cracks typically falls into three categories:

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Issue With the Drywall or Plaster (Low Concern Category) - This category covers any issue with the drywall or plaster itself, and the cause of the crack isn’t related to the framing or structure. For example, the plaster has a broken lath strip, which causes a crack, or the drywall has a poorly completed tape joint, which causes a crack. These cracks are fairly easy to fix by repairing the drywall or plaster, so they are of lower concern than a deeper moisture or structural problem.

 

Moisture Issue Causing the Framing to Swell (Medium Concern Category): Changes in moisture of the framing lumber cause minor dimensional changes, leading to drywall or plaster cracks. These moisture issues can typically be addressed with minor repairs to the roof, flashing, siding, or exhaust ducts, so cracks resulting from these issues are of medium concern.

 

Settlement / Subsidence or Heave of the House (High Concern Category): Settlement or heave of the house resulting in movement of the framing- if you have any settlement (sinking) in your house, whether it be at the foundation itself or in the framing components, this will result in movement in the framing lumber, further resulting in drywall or plaster cracks. The same is true if you have expansive soils that cause portions of the foundation to heave (lift up). These structural issues can be difficult and expensive to repair, so cracks resulting from them are a major concern.

So, how can you tell what the underlying cause of your drywall or plaster crack is? It’s tricky to determine the cause of a wall crack- we’ll want to work backwards through a process of elimination before attempting a repair. While there’s no substitute for having it evaluated by a qualified professional, if you can verify that settlement and changes in the framing moisture aren’t the cause, then you can repair the crack, and it’s unlikely to return.

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Settlement / Subsidence or Heave Cracks: Settlement cracks in a wall will form if there’s enough movement in the home's foundation or framing that the wall surface cracks.  Settlement is a general term that is used when a portion of the house is sinking, whether it be sinking in just the foundation, the framing, or both. Subsidence is a more specific term that typically refers to sinking in the foundation only. Heave occurs when expansive subgrade soils cause a lifting action. For simplicity, I’ll use "settlement" to refer to all these actions. When evaluating the cause of a wall crack and before repairing it, we want to eliminate settlement as a possible cause. If you repair a crack caused by settlement, the repair is a waste of time and money, as the crack will almost certainly return as the house continues to settle. Settlement is not normal in a house, regardless of age; a new house should not be settling. We can usually identify settlement because the floor and ceiling will be out of level in the area of the house that is sinking or heaving. For my inspections, I use a laser level and measure how level the floor and ceiling are in the area of the crack. If there is a pronounced dip in the area of the crack, the cause is settlement, and that needs to be addressed, as the crack in the wall is just a symptom of the settlement issue. The settlement could have a variety of causes, like an unsupported load in the framing or a foundation issue, and should be evaluated by an engineer. If you think you have a settlement issue, 1510 Engineering has inspected and designed repairs for countless settlement problems. We’re ready to assist with your house- Contact us or book online today.

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Moisture of the framing lumber: If the wall surface crack isn’t caused by settlement, the next item to eliminate is changes in moisture in the framing lumber. Changes in moisture of the framing lumber cause minor dimensional changes. When the moisture level in wood fibers increases, the lumber will naturally swell, while drying the lumber and thus decreasing the moisture level will cause the lumber to contract. This effect is often seen in seasonally sticking doors, where the door lumber picks up additional moisture from the surrounding air in the summertime, the door fibers swell, and the door slightly increases in size, causing it to stick in the frame. Changes in moisture in your house's framing can cause similar dimensional changes, with movement in the framing lumber resulting in drywall or plaster cracks. Rarely, minor cracks resulting from these moisture changes can occur in newer houses, as the framing lumber dries out in our dry Colorado climate. The first step to eliminating moisture as the cause of a crack will depend on where the crack is located- wall, ceiling under floor, or ceiling under attic. If the crack is in a wall or ceiling under a floor, check the wall/floor cavity for any signs of a leak allowing rainwater or snowmelt to drip in, or a bath fan or dryer vent leak expelling humid air into the cavity. If the crack is in a ceiling under an attic, check the attic and make sure it’s properly ventilated, no roof leaks, and no leaking ducts from dryer vents or bath fans, as these can dump humidity into the attic. If you’ve discovered something that indicates moisture has been entering the wall cavity, floor cavity, or attic, this will need to be addressed before you repair the crack.

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Issue with the drywall or plaster itself: You’ve eliminated settlement or moisture as the cause of your wall crack, so it’s most likely just an issue with the drywall or plaster itself. Perhaps the wall got bumped and cracked- I’ve seen playing kids or movers crack a wall. Perhaps the crack is drying shrinkage in the plaster and has been there for decades. You should be able to repair the crack, and it’s unlikely to return. 

 

This write-up has been rather technical and really only scratches the surface of these problems; they can be very nuanced. If you would like to learn more, book an appointment with me, and I’ll review your home, click Book Online. Then we can have a detailed discussion about solutions to the concerns you have with your home. I look forward to the opportunity!