Most buildings will develop cracks over their lifetime. Newer homes, 0-30yrs old, are less likely to have cracks. If significant cracking is observed in these homes further investigation may be needed as this is often a sign of structural problems. Older buildings will likely have cracks due to normal aging.

Concrete Foundations and Slabs

Concrete almost always develops cracks. These cracks are often due to shrinkage as the concrete dries and hardens, as well as temperature differentials within the concrete. Cracks less than 1/16th of an inch in a random pattern are normal shrinkage cracks. To help minimize and control cracks, control joints may be installed. Control joints are normally installed on slabs greater than 20’ square.

Problems due to cracks arise when the floor is not flush on either side of the cracks, and with wider cracks. Wider cracks may be a sign of soil settlement, insufficient reinforcing in the concrete, or an improper concrete mixture.

Concrete Walls

Concrete walls commonly develop vertical cracks as the soil under the foundation settles. In most cases, the crack is somewhat wider at the top than the bottom. If a crack is visible on the inside of the wall but not the outside, or is wider on the inside face than the outside face of the wall, this may indicate a structural problem in which the foundation wall is moving inward. If the wall surface is not flush on either side of the crack, this may also indicate movement. In these cases further structural investigation is required.

Cracks around openings such as windows and doors are also fairly common. These cracks are normally diagonal running from the corner of the opening towards the ground. If the cracks are large (1/8th inch wide or greater), further investigation may be required.

Concrete Block Foundations

Normal cracks in a concrete block foundation generally follow a step-like pattern, following the joints in the wall. This type of crack is not usually a structural problem.

As with concrete walls, cracks that are not visible or are narrower on the outside face than the inside face are indicative of inward movement and should be investigated further. Additionally, horizontal cracks often indicate inward movement of the wall and should be investigated.

Concrete block foundations perform best when reinforced both horizontally and vertically.

Concrete Block Walls Above Ground

Above ground concrete block walls are typically combined with a slab-on-grade floor with a perimeter footing which extends to below the frost depth for the given building location. The perimeter footing helps reduce the chance of cracking in the above ground walls from movements due to temperature changes. When cracked, the walls are likely to suffer from weather related deterioration.

Cracks less than 1/16th of an inch are common in above ground walls. Larger cracks, usually in a step-like pattern, may require further investigation.

As with below grade concrete block walls, the best performance is observed when proper horizontal and vertical reinforcing is provided.

Weather Tightness

The most significant result of cracking in walls, both above and below grade, is the loss of weather tightness. Proper flashing and water proofing is important for all structures. Additionally, all cracks should be kept sealed.

Wood Framing

Wood will dry out some over time, much like concrete. As a result, its shape changes over time. For this reason, some cracking and distortion of the wood is common. Normal cracks are usually seen in corners, and along the joints between a wall and ceiling. Diagonal cracking and cracking in the center of the wall are usually indicative of structural movement. The reasons for this type of cracking will vary somewhat depending on the location of the wall.

Exterior walls with cracks are likely due to foundation settlement, there will likely be cracks in the foundation as well which further indicates settlement. If the house is very new, or the cracks are growing further investigation may be warranted. If the cracking is observed on an exterior load bearing wall, the capacity of the load bearing elements may be insufficient, or the supporting members and foundations may be inadequate.

If the cracks are observed on an interior load bearing wall, as noted above, this is likely due to insufficient members. If the cracks are on non-load bearing interior walls, there may not be sufficient framing directly under the wall. It is important to place a minimum of 1 joist (usually 2 or more are used) directly below any interior wall whether load bearing or not, and not to rely on the plywood or sheathing used.

Visible Sags

Some sagging in an older home is to be expected as over time the grain structure of the wood relaxes. In a new home, any sagging is likely a sign of structural deficiency. To check for sagging look at the ridge line, tops of openings and along the main girder in the basement or first floor if the house is on a slab.

To summarize, small cracks are to be expected in most houses. If the cracks continue to grow or indicated inward movement there may be a structural problem. As a building ages, more cracks are likely to appear and the framing, mainly wood, is likely to sag.

In any case where questions are raised or you are uncertain, an engineer should be consulted.

Crawl Spaces

Homes are generally constructed over a full basement, a crawl space, or slab-on-grade. Where it isn’t possible to have a basement a crawl space is a good compromise enabling for utility space under the floor. Additionally, they are preferred where it would be difficult to maintain a dry basement, mainly in wet soil conditions.

There are many common problems associated with crawl spaces. Below is a list of the most common issues:

Moisture/Condensation – Moisture tends to accumulate in crawl spaces. If not constructed properly this may result in rot, mildew or insect infestation. Condensation may be prevented or controlled by the following:

1. Adequate Ventilation – Proper ventilation will greatly reduce the accumulation of moisture and condensation in a crawl space. Vents should be installed to provide air flow and kept open throughout the year. In cold months where freezing is a risk the vents may be closed for brief periods of time. If the vents do not provide enough ventilation, fans coupled to a humidistat can be installed.
2. All wood in contact with the ground, concrete, or concrete blocks should be pressure treated. This provides the wood with a greater resistance to moisture.
3. Crawl spaces over dirt floors should be covered with 6 mil polyethylene. To prevent tears and damage the polyethylene can be covered with sand or other materials. The joints of the polyethylene should be overlapped by a minimum of 12 to 24 inches.

Water Accumulation - Another typical problem, water accumulation will result in the same problems as moisture/condensation. To minimize water accumulation, good drainage is a must. The ground should slope away from the house to minimize water penetration. If this is not sufficient, crushed rock may be introduced to funnel the water to a sump pump.

Access – It is important to be able to access the crawl space through a hatch in the floor and/or an outside entry. Periodic inspections of the crawl space will help ensure there is no damage to the framing.

Mechanical Equipment Deterioration – One of the benefits of a crawl space is having a place to locate the mechanical equipment out of sight. If moisture collects in the crawl space the equipment will deteriorate. This is another reason to have a well ventilated and water proofed crawl space.

Insulation – There are 2 main locations for insulation in a crawl space. Either around the perimeter or on the underside of the floor. Both have advantages and disadvantages. Perimeter insulation offers more protection against freezing pipes and keeps the framing accessible for inspection. However, it creates a greater area to heat. Insulation under the floor framing reduces the area to heat, but reduces visibility of the framing for periodic inspection.

Minimum Clearance - Most current building codes require a minimum of 18 inches of clearance from the underside of the first floor framing to the floor of a crawl space. For practical application, the crawl space should have 30 inches or more between the floor and the underside of the first floor framing. When less space is offered it increases the chance of damage to the members from insects and moisture and makes it more difficult to perform visual inspections.