How Foundation Problems Can Cause Roof Damage


By Jim Oursler of Granite Foundation Repair

When your roofs are saggy or wavy, it could be a sign that your home is experiencing foundation problems. The relationship between your home's foundation and the roof is simple. The foundation is the support that carries your house. If it begins to fail, then the damage is bound to occur in other different areas, such as the roof. Simply put, if your foundation moves, so does your roof! Usually, roof damage resulting from foundation issues manifests along the ridgeline. It’s here that you’ll notice if your roof is curved or bowed. You may also notice a dip or a hump on the roofline.

Foundation problems that can cause roof damage are as follows:

1. Drainage or undercutting of the foundation
Poor drainage and undercutting are one of the common causes of foundation damage. Poor drainage mostly impacts expansive soils. Clay is a good example of an expansive soil. When in contact with water, it expands.

This expansion leads to foundation heaving. This causes your home’s foundation or concrete slab floor to move upwards. Over time, this leads to foundation cracks. To avoid this issue, a good drainage system is important. Check to see if your gutters and downspouts don’t discharge too close to your home’s foundation. Undercutting of the foundation is where water erodes the soil supporting your home’s
foundation. Common causes of undercutting are as follows:

  • A stream, creek, or river eating away at the soil near or under the foundation
  • Flooding of the home or its foundation
  • Damaged or leaking sewer line
  • Broken water line near the foundation or under it

2. Tree roots and subsidence


Tree roots are common causes of foundation problems. Usually, people think that the rubbing or falling of trees or branches is what causes roof damage. This is seldom the case. The roots are the culprits. To grow, trees require water (moisture) and nutrients. The roots absorb this moisture and lose it to the atmosphere through the leaves by transpiration.

When tree roots absorb moisture from the foundation area, the soil particles shrink. This shrinking is what causes the foundation to drop. When this drop occurs unevenly, damage to the foundation results. This foundation damage also impacts the roof. The roof will appear to be wavy, saggy or humpy.

3. Cracks or damage
Soil movement or shifting can cause the foundation to crack. Not all cracks are created equal, though. Some more serious than others. For instance, if your home’s foundation has cracks that are V-shaped (the top of the crack is wider than the bottom), then you should be worried. An example would be where the crack’s top is 3/8 of an inch wide and the crack’s bottom
is 1/8 of an inch wide. If there is significant foundation movement, you may notice the roof is bowing or sagging.

4. Foundation levels
Ideally, foundations should be level. Unfortunately, not all are. Some were constructed that way while others were as a result of soil shifting or movement. It’s normal for foundations to tilt over time. However, their levelness shouldn’t change. In some rare cases, slabs and foundations may bow or form a shape that appears concave or convex. This may occur in one area of the home or the entire home. Obviously, when a foundation is uneven the floor is also uneven. To test whether a floor is uneven, simply drop a golf ball. If it rolls, then it means your floor is sloping. The faster it rolls, the serious the foundation problem. Also, doors that are self-opening and self-closing doors could signal that your home’s floors are uneven.

5. Settling and heaving


Homes built on soil that is poor or shifting will tend to move or settle somewhat. Settling is normal for new homes. But, if the settling continues past two years, it could signal a problem. If this settling is uneven, the roof will most likely reflect this. Settlement or heaving is especially common in areas with expansive clay soils. During the dry season, the foundation unevenly sinks downwards. During the wet season, the soil swells and heaves up. Typically, this uneven settlement or heaving is what causes roof problems.

Non-Foundation Causes of Roof Damage

Roof sagging or waviness can also be caused by other factors aside from foundation issues. Such factors include:

  • Poor workmanship
  • Improper design or engineering
  • Cracked or damaged rafters or trusses
  • A new roof that is of a heavier material
  • Two or more roofs

While your foundation and your roof are in opposite locations, they are very much connected. If your home’s foundation moves or shifts, then it’s likely your roof will also become wavy or saggy.

If you notice anything unusual with either your roof or foundation, it’s best to have it professionally inspected.