What to Put Down Before Building a Deck: A Comprehensive Guide

Building a deck is an exciting project that can significantly enhance your outdoor living space. However, before you start hammering and screwing, it’s crucial to lay the proper foundation. What you put down before constructing your deck directly impacts its longevity, stability, and even your enjoyment of it. This comprehensive guide will walk you through the essential steps and materials needed to prepare the ground beneath your new deck.

Table of Contents

Understanding the Importance of Proper Preparation

The ground beneath your deck isn’t just empty space. It’s a dynamic environment susceptible to moisture, weed growth, and even pest infestations. Ignoring this space can lead to a host of problems down the road, including:

Structural Instability: Uneven ground or insufficient support can cause your deck to sag, warp, or even collapse over time.
Weed Infestation: Weeds growing up through the deck boards are unsightly and can damage the structure.
Moisture Damage: Trapped moisture can lead to rot, decay, and mold growth, shortening the lifespan of your deck.
Pest Problems: Insects and rodents can find shelter under your deck, causing damage to the wood and potentially entering your home.

Therefore, investing time and effort in proper ground preparation is an investment in the long-term health and beauty of your deck.

Initial Assessment and Planning

Before you even consider what materials to put down, you need to assess your site and plan accordingly.

Site Inspection

Start by thoroughly inspecting the area where you plan to build your deck. Consider the following factors:

Soil Type: Is it clay, sand, or a mix? Clay soils retain more moisture, while sandy soils drain quickly. This will influence your drainage solutions.
Slope: Is the ground level or sloped? Sloped ground may require more extensive excavation and leveling.
Existing Vegetation: What kind of plants are currently growing in the area? You’ll need to remove them thoroughly.
Proximity to Your Home: How close will the deck be to your house? This can affect building codes and drainage requirements.
Underground Utilities: Always call your local utility companies before digging to avoid damaging underground lines.

Planning Your Deck Design

Your deck design will also influence your ground preparation strategy. Consider the following:

Deck Height: A low-to-the-ground deck will require different preparation than an elevated deck. Low-profile decks may need better weed control and moisture barriers.
Deck Size: The larger the deck, the more material you’ll need to cover the ground underneath.
Deck Material: The type of decking material you choose (wood, composite, etc.) can also affect your ground preparation needs.

Essential Steps for Ground Preparation

Once you’ve assessed your site and planned your deck design, you can begin the ground preparation process.

Clearing the Area

The first step is to clear the area of all vegetation, debris, and obstructions. This includes:

Removing Plants: Dig out all plants, including their roots. Herbicide can be used, but be sure to follow the manufacturer’s instructions carefully and choose a product that won’t harm your soil.
Removing Debris: Clear away any rocks, branches, leaves, or other debris.
Removing Topsoil: In some cases, you may need to remove the top layer of topsoil, especially if it’s rich in organic matter. This will help prevent weed growth.

Leveling the Ground

Leveling the ground is crucial for ensuring a stable and even deck surface.

Excavation: If the ground is uneven, you may need to excavate some areas and fill in others. Use a shovel, pickaxe, and wheelbarrow to move soil as needed.
Compaction: Once the ground is level, compact the soil using a hand tamper or a plate compactor. This will help prevent settling and ensure a solid base.
Checking for Level: Use a level and a long, straight board to check for level in all directions. Make any necessary adjustments.

Creating Proper Drainage

Proper drainage is essential for preventing moisture damage. Standing water under your deck can lead to rot, mold, and other problems.

Grading: Grade the ground away from your house to ensure that water flows away from the foundation. A slight slope is usually sufficient.
Adding Gravel: A layer of gravel can help improve drainage. Spread a 4-6 inch layer of gravel over the prepared ground.
Installing Drainage Systems: In areas with poor drainage, you may need to install a more elaborate drainage system, such as a French drain or a sump pump.

Choosing the Right Ground Cover

Once you’ve cleared, leveled, and graded the ground, it’s time to choose a ground cover to prevent weed growth, control moisture, and deter pests.

Gravel: A Popular and Versatile Option

Gravel is a popular choice for ground cover under decks for several reasons:

Excellent Drainage: Gravel allows water to drain quickly, preventing standing water and moisture buildup.
Weed Control: Gravel helps suppress weed growth by blocking sunlight and preventing seeds from germinating.
Pest Deterrent: Gravel can deter some pests, such as rodents and insects, by making it difficult for them to burrow and nest.
Affordable: Gravel is relatively inexpensive and readily available.
Types of Gravel: Pea gravel, crushed stone, and river rock are all suitable options for ground cover.

Landscape Fabric: An Effective Weed Barrier

Landscape fabric is another popular choice for ground cover under decks.

Weed Prevention: Landscape fabric is designed to block sunlight and prevent weeds from growing.
Moisture Control: Some types of landscape fabric allow water to pass through, while others are impermeable. Choose the right type for your specific needs.
Easy Installation: Landscape fabric is relatively easy to install. Simply unroll it and cut it to fit the area.
Durability: Landscape fabric is available in different thicknesses and durability levels. Choose a durable fabric that will withstand the elements.
Installation Tip: Overlap the edges of the fabric to prevent weeds from growing through the seams. Secure the fabric with landscape staples.

Plastic Sheeting: A Moisture Barrier Option

Plastic sheeting can be used as a moisture barrier under your deck.

Moisture Prevention: Plastic sheeting prevents moisture from evaporating from the ground and condensing on the underside of your deck.
Weed Control: Plastic sheeting also helps suppress weed growth.
Considerations: However, plastic sheeting can also trap moisture, so it’s important to ensure that there is adequate drainage. In some cases, plastic sheeting may not be the best option.

Combination Approaches

Often, the best approach is to combine different types of ground cover. For example, you might use a layer of gravel topped with landscape fabric. This will provide excellent drainage, weed control, and pest deterrence.

Additional Considerations

In addition to the essential steps and materials outlined above, there are a few other considerations to keep in mind.

Building Codes and Regulations

Be sure to check your local building codes and regulations before starting your deck project. Some areas may have specific requirements for ground preparation, drainage, and weed control.

Pest Control Measures

Consider taking additional pest control measures to protect your deck from damage. This might include:

Treating the Soil: Apply a soil treatment to prevent termites and other insects from infesting the wood.
Using Pest-Resistant Materials: Choose decking materials that are naturally resistant to pests, such as redwood or cedar.
Installing Pest Barriers: Install pest barriers around the perimeter of your deck to prevent rodents and insects from entering.

Ongoing Maintenance

Once your deck is built, it’s important to perform regular maintenance to keep it in good condition. This includes:

Removing Debris: Regularly sweep or blow away leaves, twigs, and other debris from under the deck.
Checking for Weeds: Inspect the area for weeds and remove them promptly.
Inspecting for Moisture Damage: Check for signs of rot, mold, or other moisture damage.

By following these steps and taking these considerations into account, you can ensure that your deck is built on a solid foundation and will provide years of enjoyment.

Material Comparison Table

Material	Pros	Cons	Best Use
Gravel	Excellent drainage, weed control, pest deterrent, affordable	Can be difficult to walk on, may require periodic replenishment	General ground cover, especially for areas with poor drainage
Landscape Fabric	Effective weed barrier, easy to install	Can tear or degrade over time, some types may restrict drainage	Weed control under gravel or as a standalone barrier
Plastic Sheeting	Moisture barrier, weed control	Can trap moisture, may not be suitable for all climates	Moisture control in dry climates with good drainage

Conclusion

Proper ground preparation is the foundation for a long-lasting and enjoyable deck. By taking the time to clear, level, and protect the ground beneath your deck, you can prevent a host of problems and ensure that your outdoor living space remains beautiful and functional for years to come. Choosing the right materials, like gravel or landscape fabric, and considering factors like drainage and pest control, are crucial steps in this process. Remember to always check local building codes and prioritize safety throughout the construction process. Your diligent preparation will pay off with a stunning and durable deck that you can enjoy for many years.

Why is it important to put something down before building a deck?

It’s vital to prepare the ground before deck construction to prevent future problems. Moisture from the soil can lead to rot and decay in the deck’s substructure, particularly if it’s made of wood. Additionally, vegetation growth under the deck can create a breeding ground for insects and rodents, potentially causing damage to the deck and surrounding property.

Proper ground preparation minimizes these risks by creating a barrier against moisture, inhibiting weed growth, and discouraging pests. This ultimately extends the lifespan of the deck, reduces maintenance needs, and contributes to a safer and more enjoyable outdoor space. Ignoring this step can lead to costly repairs and potentially compromise the structural integrity of the deck over time.

What are the most common materials used as a ground barrier under a deck?

The most common materials used as a ground barrier under a deck include landscape fabric, plastic sheeting, and gravel. Landscape fabric is a permeable material that allows water to drain through while preventing weed growth. It’s a relatively inexpensive option and easy to install, making it a popular choice for many homeowners.

Plastic sheeting, such as polyethylene, provides a waterproof barrier, effectively blocking moisture from rising from the soil. However, it’s important to ensure proper drainage to prevent water from pooling on top of the sheeting. Gravel, especially crushed stone, offers excellent drainage and helps to suppress weed growth. It’s a more durable and long-lasting option compared to landscape fabric or plastic sheeting.

How do I prepare the ground before laying down the ground barrier?

Ground preparation begins with removing any existing vegetation, including grass, weeds, and roots, from the area where the deck will be built. This ensures a level surface and prevents future growth from pushing through the barrier. Using a shovel or tiller, loosen the soil to make it easier to remove the vegetation and level the ground.

Next, compact the soil using a hand tamper or plate compactor to create a stable base for the ground barrier. Leveling the ground is crucial for proper drainage and preventing water from pooling under the deck. Once the soil is compacted and level, you’re ready to lay down your chosen ground barrier material.

How do I install landscape fabric under a deck?

Start by unrolling the landscape fabric across the prepared ground, overlapping each section by at least 12 inches. This overlap ensures that weeds cannot penetrate the seams. Secure the fabric in place using landscape staples, spaced about 12 to 18 inches apart along the edges and throughout the fabric.

Pay particular attention to securing the fabric around posts or other obstructions, cutting the fabric to fit snugly around them and using staples to hold it in place. If using multiple layers of fabric, stagger the overlaps to further enhance weed prevention. Proper installation is key to maximizing the effectiveness of landscape fabric as a ground barrier.

What are the pros and cons of using gravel as a ground barrier under a deck?

Gravel offers several advantages as a ground barrier, including excellent drainage, weed suppression, and durability. It allows water to drain away from the deck, preventing moisture buildup and reducing the risk of rot. Gravel also provides a stable and long-lasting barrier against weed growth, minimizing maintenance needs.

However, gravel can be more expensive than other options like landscape fabric or plastic sheeting. It also requires more effort to install, as it needs to be spread evenly and compacted. Additionally, gravel can be difficult to remove if you ever need to access the ground beneath the deck for repairs or maintenance.

How much gravel should I use as a ground barrier under a deck?

A good rule of thumb is to use at least 4 to 6 inches of gravel as a ground barrier under a deck. This depth provides adequate drainage and weed suppression. When spreading the gravel, ensure that it’s evenly distributed across the prepared ground.

After spreading the gravel, use a rake or shovel to level it out. Compacting the gravel is also recommended to create a more stable and effective barrier. You can use a hand tamper or plate compactor to compact the gravel, ensuring it’s firmly in place.

What are some alternative solutions for ground preparation if I don’t want to use fabric, plastic, or gravel?

For those seeking alternatives to traditional ground barriers, consider using recycled rubber mulch or a thick layer of wood chips. Recycled rubber mulch is durable, provides good drainage, and inhibits weed growth. Wood chips, particularly cedar or redwood, offer natural resistance to decay and pests, but require occasional replenishment.

Another option is to create a concrete slab beneath the deck. This provides a solid, impenetrable barrier against moisture and pests, but is a more expensive and labor-intensive solution. Regardless of the chosen material, proper site preparation, including vegetation removal and leveling, remains crucial for optimal performance.