Seasonal temperatures and varying precipitation may cause cracking in your sidewalks and driveway. Frost penetration can also cause heaving or settlement and change the direction of surface drainage. Sometimes, damaged areas return to their original position in warm weather. In most cases, these issues are beyond the control of the builder.
Your driveway was constructed for use by light vehicles—not for heavy trucks or equipment, even for a short period of time. Seal your concrete annually to increase its longevity.
Why is my concrete damaged?
Concrete is a mixture of stone and sand called ‘aggregate’ combined with water and cementing materials. As concrete is placed and finished, the aggregate settles into the paste, causing a thin layer of paste to rise above the aggregate. The paste layer can separate from the main body of the concrete. When the fine, top layer of the paste peels away, the concrete is said to be ‘mortar flaking.’ When the separation occurs as circular/oval pieces across several sections of aggregate, it’s called ‘spalling.’ When the separation occurs as small holes above a piece of aggregate, it’s called ‘pitting.’
Surface impact, weathering and freeze/thaw cycles are the most common causes of flaking, spalling and pitting. Salts and de-icers can also cause spalling and pitting. In some cases, improperly-cured concrete or the corrosion of rebar can also cause separation. In rare cases, the aggregate can be contaminated by materials that expand when wet or heated (e.g. ironstone or organic matter) and cause pitting. Sometimes, the contaminated material can also pop out and leave a hole or raised spot in the concrete.
Quality mix and proper installation and curing will significantly reduce the likelihood of these defects and are in the hands of the builder. The following measures will increase your chances of a successful concrete installation:
- Use air-entrained concrete mixes with a low water-to-cement mix ratio
- Delay finishing until the water sheen on the concrete surface is gone
- Edge the concrete near forms
- Use isolation joints and construction joints where appropriate
- Do not power-trowel concrete subject to freeze-thaw cycles and de-icing chemicals.
How can I protect my concrete?
The application of a breathable surface sealer can reduce damage caused by de-icing and road salts. Silane and siloxane are the two most common sealers. These sealers can penetrate concrete as deep as three millimeters while still allowing the concrete to breath. This prevents vapour pressure from building up between the concrete and sealer. Because the sealer is embedded within the concrete, it’s more durable to abrasive forces and ultraviolet deterioration, providing longer-lasting protection.
Treatment and re-treatment should be carried out according to manufacturers’ directions but some guidelines apply to all sealers:
- Wait at least 28 days before applying sealer to new concrete
- Sealer should only be applied to clean concrete left to dry for at least 24 hours at temperatures above 16°C
- Penetrating sealers cannot fill surface voids that are filled with water
- Concrete should be clean
- Concrete placed in late fall should not be sealed until spring because the sealer may cause the concrete to retain water and increase the likelihood for freeze-thaw damage.
Basement walls are subjected to many stresses. For example, the base of the wall (below grade) maintains a fairly uniform temperature but the portion above grade is exposed to seasonal temperature variations. These temperature changes can cause the wall to shift or crack.
How can I keep water from penetrating my concrete foundation walls or floor?
Moisture is always present in soil. The amount of moisture will increase in the spring when snow begins to melt and during heavy or prolonged rains. Builders take measures to ensure water does not accumulate against the foundation walls or under the basement slab. Moving surface water away from the foundation is the best way to protect your home from water penetration.
Unless there is an unusual amount of water accumulating against the foundation (such as in a severe rainstorm or from poorly maintained grade around the foundation), large amounts of water should not flow into the basement.
However, concrete is a porous material and any coatings applied to the walls to repel water do not go under the footing the wall rests on. In this space, small amounts of water may be transferred through the concrete and show up as dampness on the inside of the concrete wall.
Make sure you are prepared to manage water if it does enter the basement. Check your sump pit and pump in the spring and fall to ensure the pump is operational, the power cord is in good shape, the pipes are connected and the pump turns on when the float is lifted.
As a homeowner, you are responsible to make sure systems put in place by your builder are maintained and working as intended to prevent unnecessary water damage to your property. Refer to the Surface Water Management Guide for reminders of what you can do to reduce the risk of water damage to your home.
Why is my basement floor damp and how do I reduce the moisture?
Concrete basement floors sometimes feel damp to the touch. This damp feel is due to one of two factors: First, the amount of water present in new concrete. After being poured, concrete contains an amount of water that will evaporate to the inside of the basement and possibly create a damp floor. Avoid placing materials such as carpet or boxes directly on the floor for the first year after a basement floor is poured.
Second, there may be small voids in the concrete that act like tiny straws, drawing small amounts of water from the soil into the basement slab. The rate of this movement depends on the amount of moisture under the slab, the relative humidity of the basement and the porosity of the concrete. If the basement is very dry and the ground is very wet, the flow of water will be quicker.
You can stop this flow of water by breaking the connection between the source of moisture under the slab and the slab itself. Builders use measures such as granular fill, polyethylene membrane or foam insulation underneath the basement floor slab to create this break.
If the dampness persists, consider installing a de-humidifier or increasing the amount of ventilation in the area. Moving surface water away from your foundation will also reduce opportunities for water penetration.
Before you apply any finish over a concrete floor (paint, carpet, solid flooring), make sure the concrete is dry.
Floor drains are usually located next to the furnace to help remove water spilled on the basement floor and, in some cases, for the drainage of water condensation from the chimney of a high efficiency furnace.
To prevent sewer gas from entering your home through floor drains, make sure water is always present in the drains. To test if your drains have water in them, pour a little water into the drain and listen. You should hear if the water hits more water or if it hits the bottom of the trap. Every few months or if you smell sewer gas, pour a bucket of water down the drain to re-establish the water seal.
Some cracking in a garage slab is common and will not impact the floor’s performance. Contractors may cut control joints to provide a line for the cracking to follow.