Getting a new driveway installation is a significant home improvement project that can greatly enhance both the functionality and curb appeal of your property. Whether you’re looking to replace an outdated or damaged driveway or you’re adding a new one to a recently developed property, the process involves several important steps, considerations, and decisions. Here’s an in-depth look at some Q & A's that we address quite often as a Beaverton driveway contractor.
Here are a couple of questions as concrete contractors we get asked A LOT!
Can you pour concrete over concrete to level it out?
Yes, but.....
Crack Propagation: Concrete naturally cracks under stress, and if the old slab already has cracks, a new, unreinforced concrete layer is likely to crack in a similar pattern, as the deformation will concentrate at those pre-existing weak points. This is why you might see the new layer cracking right above the old cracks—essentially, the cracks in the old concrete "guide" where the new concrete will fail, much like bending a cracked glass plate.
Thickness of the New Pour: Pouring a very thin new layer (e.g., 4-5 cm) over an old slab can seem tempting, but it's not ideal because it won't offer enough strength to resist cracking. Typically, for a new floor, around 15-20 cm of doubly reinforced concrete is recommended, depending on the conditions. Thin, unreinforced layers over an existing slab will not provide adequate durability and can fail prematurely.
Reinforcement: Adding reinforcement (e.g., steel bars) can help improve the durability of a thinner layer, but as you mentioned, the reinforcement will rust over time, especially in a thin concrete slab. This is a short-term fix and might be acceptable if you're planning to sell the house soon.
Fiber-Reinforced Concrete: Using a thin (5 cm) layer of fiber-reinforced concrete, as you suggested, could be a creative solution. The mesh layers of fiberglass in the concrete can help distribute stresses more evenly and prevent cracking, as long as it's done correctly. This method is quite labor-intensive, but it's an innovative way to reinforce thin concrete layers without relying on traditional rebar. The key challenge here, as you pointed out, is managing the curing process and avoiding deformation during the application.
Paving Over the Old Floor: One of your final suggestions is to pave over the old concrete slab with street-grade pavement stones. This approach offers a number of benefits: it avoids the risks of settlement cracking, allows for drainage, and is relatively low cost, especially if you can source used stones. It also gives a more aesthetically pleasing finish and is a solution that doesn't rely on bonding or reinforcing concrete directly.
Ultimately, the best solution will depend on the long-term goals for the space and how much time and effort you’re willing to invest. If you want something that lasts, a solid, properly reinforced concrete pour is ideal. But for more temporary fixes, the fiber-reinforced layer or even the pavement stone approach could be good alternatives.
How can I fix cracks in my old concrete driveway without replacing it completely (and having to pay someone)?
Concrete Movement and Cracking: Concrete, though strong and rigid, needs to expand and contract with temperature and moisture changes. Without proper allowances (like expansion joints), these movements can cause cracks. Once a crack forms, it can allow water to seep through, which weakens the soil beneath the slab.
Soil Erosion and Voids: The cracks allow water to flow under the concrete, and if the slab isn't on a proper drainage base, the soil becomes weakened. Over time, this leads to the formation of voids beneath the slab, causing it to shift and eventually break under weight, like vehicles driving over it.
Solution:
Filling the Cracks with Sand: By using fine-grade children's play sand, you’ve addressed the issue of water infiltrating the cracks and further eroding the soil underneath. The sand fills the cracks and voids, helping to re-support the slab. You recommend dry sand because wet sand won't flow easily into the cracks, and vibration (from a mallet) and brushing (with a broom) help settle the sand into the voids.
Sealing the Cracks: After filling the cracks with sand, you use a liquid cement crack filler to seal the surface cracks. While this doesn't "heal" the cracks, it prevents further water infiltration, stopping new cracks from forming and halting the movement of the slab. This effectively stabilizes the concrete and prevents the worsening of the damage.
Results:
Long-Term Effectiveness: You’ve found that your driveway, after using this method, stopped moving and prevented further cracking for six years. While this doesn’t fix the existing cracks, it addresses the root cause of further deterioration—water weakening the underlying soil.
Practical and Cost-Effective: The method you described is relatively simple, uses affordable materials (sand and crack filler), and requires minimal equipment. This makes it an appealing solution for homeowners facing similar issues.
Limitations:
Temporary Fix: While the method can slow further cracking and stabilize the slab for some time, it’s a temporary solution. The underlying causes—water infiltration, soil erosion, and settlement—are still at play. Over time, more cracks may appear, especially if the soil underneath is still unstable or poorly drained.
Works Best for Smaller Cracks: This method seems more suited to cracks that have already formed and are not too large. It's also useful for smaller voids under the slab, where the sand can effectively settle and provide support. Larger voids or deep cracks may require more extensive repairs or even re-leveling the concrete.
These are good short-term solution to slowing further damage to a concrete slab, especially in driveways and sidewalks. By addressing the issue of water infiltration and reinforcing the slab from beneath with sand and sealing the surface with crack filler, you've managed to prolong the lifespan of your driveway. It’s a smart way to buy time until more extensive repairs, like re-pouring or re-leveling, are necessary—or, in some cases, it might be enough to maintain the driveway in usable condition for many years.
My cement driveway is 24 years old and crumbing. Is it cheaper to replace it with cement or asphalt?
Asphalt (Blacktop):
Cheaper and Faster: As you rightly pointed out, asphalt is cheaper and quicker to install than concrete. It requires less preparation and labor to lay down, making it an attractive option for many homeowners on a budget or for projects with tight timelines.
Less Durable: Asphalt, however, tends to have shorter lifespan and less durability compared to concrete. It’s more susceptible to wear and tear from traffic, weather, and environmental factors. The edges of asphalt roads often deteriorate over time because they lack the rigidity and long-lasting strength of concrete. Asphalt also tends to soften and degrade more quickly in hot weather.
Potholes and Maintenance: One of the most common issues with asphalt is the formation of potholes, which happen due to the material's tendency to crack and break down over time. These potholes require frequent repairs, adding to long-term maintenance costs. Asphalt also tends to crumble along edges and seams, creating a less aesthetically pleasing and functional surface over the years.
Best for Low-Traffic Areas: Given its lower durability, asphalt is a good option for areas with light traffic or less weight, such as foot paths, pads under boats or RVs, and other temporary or low-demand applications.
Concrete:
Long-Lasting and Durable: Concrete has a much longer lifespan than asphalt. As you mentioned, modern concrete mixes can easily last 20 years or more with minimal maintenance. Concrete is less prone to cracking under heavy loads, and it performs better in extreme weather conditions—whether it’s freezing winters or hot summers.
Aesthetics and Variety: Concrete has evolved in terms of aesthetic variety. The newer acid wash stains you mentioned can give concrete a much more polished, decorative finish, making it an attractive choice for driveways, patios, and other visible areas. Concrete can also be textured, stamped, or colored to mimic materials like stone or brick, allowing for more customization compared to asphalt.
Airport Runways as an Example: Your observation about airport runways being made from concrete is spot-on. Airports require a surface that can withstand massive loads (like airplanes), extreme weather, and long-term wear, making concrete the obvious choice for durability and strength.
Maintenance and Cost-Effectiveness: Although concrete has a higher initial cost than asphalt, over time, it tends to be the cheapest in terms of maintenance and longevity. Asphalt requires periodic repairs, resealing, and resurfacing, while concrete, once properly installed, needs little maintenance besides cleaning and occasional crack filling (if any). Over the course of several years, the total cost of a concrete driveway can be significantly lower than asphalt, particularly if the homeowner values low maintenance and long-term durability.
Choosing Between Asphalt and Concrete:
Budget Considerations: If cost is the primary concern and you’re willing to accept more frequent repairs and shorter lifespan, asphalt is the more economical choice in the short term. It’s great for low-traffic areas or temporary surfaces.
Long-Term Value: If you're looking for something that lasts and requires less maintenance in the long run, concrete is the better option. Over time, it provides better value despite the higher upfront costs. With modern concrete mixes and finishes, you also get aesthetic options that can enhance curb appeal and boost the property's value.
Specific Use Cases: For heavier use areas like driveways that will endure cars, trucks, or even RVs, concrete is the more durable option. Asphalt works well in situations where cost is a bigger priority or the surface won’t be subjected to heavy loads or extreme conditions.
Both asphalt and concrete have their place, and the decision largely depends on budget, desired longevity, and the intended use of the paved surface. Asphalt is excellent for lower-cost, quicker installations in areas with light traffic, while concrete, though more expensive initially, offers a longer-lasting, low-maintenance, and highly durable surface. In many cases, concrete can indeed end up being the most cost-effective option over the long run, especially for driveways that need to withstand years of use.
How do you level a concrete floor that slopes?
1. Determining the Slope:
Assessing the Slope: The first step is always to measure the existing slope using a self-leveling laser or a similar device. This helps determine how much correction is needed. A small slope may not require drastic measures, while a significant slope demands more careful planning.
Flat vs. Level: It's important to note that while floors should be flat for usability (especially for laying tiles, flooring, etc.), they don’t always need to be perfectly level unless the intended use of the room requires it (e.g., water drainage in a bathroom or kitchen).
2. Mild Slopes:
For minor slopes, a self-leveling compound is often sufficient. These are usually poured wet over the floor, and the compound naturally finds its level, filling in low spots. Once it dries, the floor is flat and stable. This is a relatively straightforward and cost-effective solution for small unevenness in a floor.
3. More Extreme Slopes:
Severe Slope Adjustment: If the slope is significant (like in a basement or garage), a more intensive approach is needed:
Pea Gravel and Concrete: As you mentioned, for a sloped basement, bringing in a dump truck of pea gravel followed by a concrete pour could fill in the low areas. The gravel serves as a stable base to raise the floor level, and a concrete layer is then added on top. This method works well in spaces with extreme slopes (e.g., 7 inches or more).
Professional Leveling: For large or complex leveling jobs, bringing in a professional company that uses laser-leveled screed systems can be a good option. These systems can level the floor with high precision, ensuring an even finish. While more expensive, this approach guarantees a perfect result, especially for large rooms or high-traffic areas.
4. Garage Floor Leveling:
Concrete Slurry: Garage floors are often tricky because they need a lot of concrete to level out the slope, but using a lot of gravel or rocks is usually undesirable. One way to address this is by pouring a concrete slurry over the entire floor, which provides a smooth, even finish without the bulk of traditional concrete pours.
Retaining Wall: If the slope is severe, you may need to build a retaining wall around the garage door to prevent the slurry from spilling out. In some cases, this can mean a complete overhaul of the wall and entryway, which is more labor-intensive but necessary for a clean, professional look.
5. Alternative Methods:
Suspended Floor with Wood Stringers: For certain applications, like garages, another option you’ve used is to suspend the floor by creating a framework with wood stringers and shims. This method can work well for smaller, less extreme slopes and where you want a relatively quick and simple fix. The floor can be suspended at the correct height, and shims are used to level it out.
6. Choosing the Right Approach:
Assessing Severity: The key takeaway is that you need to assess the severity of the slope in your project before choosing a solution. For minor slopes, a simple self-leveling compound is probably sufficient. For more extreme slopes, consider the cost and complexity of options like professional services, concrete slurry, or creating a suspended floor.
Tackling It Accordingly: If you’re dealing with a small, manageable project, DIY methods like pouring leveling compounds or using shims can work well. For larger, more complex jobs, it’s best to consult professionals who can provide a higher-quality, long-term solution.
Floor leveling requires a clear understanding of the slope and its impact on the space. Minor slopes can usually be fixed with self-leveling compounds, while more severe cases might require additional material (like pea gravel) or professional-leveling systems. For specific spaces like garages, a slurry pour may be ideal, and in other cases, using wood stringers to suspend the floor could be a viable solution. Whatever the method, always assess the project’s severity before deciding on the approach.
Let us know what you think!
Thanks for learning with your local Portland and Beaverton driveway contractors.
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