Are you looking to create an inviting outdoor space but worried about losing your trees in the process? In this guide, the team at Koch & Associates explains how to design hardscapes and patios around trees. Learn about the materials, design strategies, and root protection techniques you can use to install hardscapes and patios without harming your trees.

Why Solid Concrete Is the Wrong Choice Near Trees

Poured concrete is often the first material homeowners consider when designing a patio. But if trees are growing nearby, it is actually one of the worst choices you can make. Roots need water, oxygen, and space to grow. A solid concrete slab denies them all three by sealing off the soil, blocking rainfall, and leaving roots nowhere to go. The good news is that you don’t have to put your patio dreams on hold. In the sections below, we will cover design approaches that create attractive hardscapes without putting tree health at risk. 

A Guide to Tree-Safe Hardscaping

Material Selection

When planning a patio or hardscape near trees, your choice of materials is important. Instead of solid concrete, look for options that allow water and air to filter into the soil and give roots room to grow. Here are a few hardscape materials popular with Bay Area homeowners: 

• Permeable pavers set in gravel: Permeable pavers feature an open structure that allows water and air to drain into the soil below. It is important to lay this material on a gravel base, as wet sand can compact and stop air and water from reaching the root zone.

• Flagstone with open joints: These natural stones can be set with open gaps between each piece instead of tight mortar joints. Filling those gaps with gravel or low-growing groundcover gives your space a one-of-a-kind appearance.

• Decomposed granite: Derived from naturally weathered granite, this gravel-like material compacts into a firm surface that is great for winding garden paths and informal seating areas. It is less likely to become dislodged and migrate out of the area like traditional gravel.

• Gravel or crushed stone: Gravel is the most permeable hardscape surface available and works well for areas where a natural look complements your design. However, unlike decomposed granite, it will shift and spread without protective borders to keep it in place.

Tree Wells

A tree well is a planned opening left in a patio or walkway surface that encircles the base of a tree. This open area improves air and water movement to the root zone and reduces the risk of damage to the trunk and roots over time. It is important to follow these best practices when creating a tree well:

• Size: Make sure your tree well is at least one and a half times the diameter of the tree trunk to provide enough space for growth.

• Mulching material: Use a light layer of bark mulch, wood chips, or other organic material inside the well. These help retain soil moisture, suppress weeds, and add nutrients as they break down. Do not bury the tree’s trunk with soil or mulch.

• Protection: Avoid placing heavy materials or allowing frequent foot traffic within this area. 

• Edging: Install a stone, metal, or plastic border around the perimeter of a tree well for a tidy and finished look.

Retaining Walls

Retaining walls are the rare hardscape element that can benefit your trees. On sloped properties, these structures help control soil erosion and stabilize the ground around root zones. However, they can also cause damage if not carefully installed. Here are a few considerations to keep in mind when designing a retaining wall:

• Avoid changing the soil grade near trees: Raising the soil level suffocates roots by cutting off oxygen, while lowering it can sever roots directly. Even a few inches of change within the root zone can cause serious decline.

• Choose dry-stacked construction where possible: Solid mortared walls can redirect water away from the root zone entirely. On the other hand, dry-stacked walls allow water to pass through the gaps and into the soil below.

• Include weep holes or drainage: Without adequate drainage, water can build up behind a retaining wall and saturate the soil around the root zone. Waterlogged soil can lead to pests, root damage, and tree death.

Root Protection Techniques

Even the best materials and design choices cannot protect a tree from a careless construction process. Equipment, soil compaction, and accidental root damage can cause harm that may not become visible until months after the project is complete. Here are a few key steps to take before and during construction:

• Map out critical root zones: The critical root zone is the location of a tree’s primary feeder roots and extends roughly one foot outward for every inch of trunk diameter. Mapping it before construction will help you plan safe excavation routes, post placement, and hardscape design.

• Fence off trees during construction: Temporary fencing around the root zone is a great way to ensure heavy equipment, materials, and foot traffic won’t damage your tree. Soil compaction from machinery is one of the most common and preventable causes of post-construction tree decline.

• Manually dig near roots when necessary: Digging by hand reduces the risk of severing major roots. If you do sever a root, use a sharp tool to make a clean cut instead of leaving it jagged.

• Consult a certified arborist before breaking ground: An arborist can assess your trees, map their root zones, and point out issues that may arise during construction.

Need Help Designing a Hardscape or Patio Around Trees? 

At Koch Landscape Design, we believe that mature trees are one of the most valuable features of your property. That is why we have spent over 40 years helping Bay Area homeowners treat them as a focal point instead of an obstacle. Need help deciding next steps? Reach out to our team for a discovery meeting in Palo Alto, Los Altos, Los Altos Hills, Los Gatos, Mountain View, or San Jose.

Call 510-490-0487 to get in touch with Koch & Associates in the Bay Area. Have more questions about how to design hardscapes and patios around trees? Contact us online.