How to Design and Build Planter Boxes Without Damaging Your Foundation

Installing a flower bed against your house foundation can improve the appearance of your home and add valuable space for gardening. When you design your planter box, you will need to make sure your foundation is protected from damage that can be caused by watering and growing plants.

This article will explain how to make the right decisions when planning to add a flower bed or raised planter next to your foundation.

Here, you will find out easy ways to create proper drainage to prevent soil erosion and damage and give your plants the best chance to grow big and strong.

Can You Build Flower Beds Next to the House Foundation?

There is a tremendous amount of debate out there in professional circles about whether it is safe to build planter boxes next to the house foundation. One thing that is agreed upon is that boxes should not use the foundation as a back wall. What that means is you should plan to have space between the flower bed and your house foundation.

The amount of space required varies, with many experts agreeing that four inches are the minimum distance you should provide between the foundation and a flower bed. It’s also a good idea to prevent moisture accumulation behind and around boxes, so you should consider using gravel and rocks to increase drainage.

Common Problems From Foundation Flower Boxes

Common problems homeowners encounter caused by planter boxes near foundations include:

  • Expansion problems
  • Erosion problems
  • Pest problems
  • Mold, Mildew, and Fungus problems

The type of foundation you have will make a difference when avoiding problems from a flower box or plant bed. We will discuss the types of foundations and the problems that are caused by improperly built planter boxes.

Many homes in the United States use poured concrete foundations, either as a slab or as a wall buried in the ground. The concrete is treated with tar or another substance to prevent water from penetrating into the concrete.

This treatment works great for limited moisture accumulation, such as when it rains. But, when you are watering a flower box every day, you are risking creating the perfect environment for damage to happen.

Flower beds and planter boxes can create problems with poured concrete foundations in a couple of ways. The greatest problem is excess water retained in the soil. Without proper drainage, accumulated water will eventually penetrate the concrete and weep moisture into crawl spaces and basements. The most common problems can all be avoided by providing proper drainage.

– Expansion Problems

Water, soil, and concrete all expand and contract with changes in the weather, but at different rates. For example, when water freezes, it expands. If water has begun to seep into the concrete foundation, freezing temperatures can cause the concrete to crack.

Sometimes, these cracks are minor and do not cause problems for the house, but that isn’t always the case. Serious structural failure can be caused by water freezing and splitting foundations.

– Erosion Problems

Over time, watering a flower bed that is against the foundation can cause erosion. This condition can cause failures as the concrete settles and can collapse walls and sag rooflines. Repairing soil erosion damage to a foundation can be extremely expensive. Erosion is a serious problem for older houses using pier block foundations, too.

– Pest Problems

Flower beds against foundations are a haven for critters and pests. If the space between the planter and the house is too small, dead leaves and dirt will accumulate, and these are prime locations for cockroaches, rodents, and termites.

– Mold, Mildew, and Fungus Problems

Moisture is essential for mold, mildew, and fungus, making improperly draining planter boxes. Many types of mold and mildew can cause respiratory ailments and can result in long-term health problems.

The fungus is unsightly and can harm desirable plants in your garden.

Designing for Proper Drainage

The first step to ensuring that a planter box or flower bed won’t damage your foundation is to design for proper drainage. How you design your drainage system will be determined by the type of planter you build.

Before building a planter box or flower bed, you’ll need to make sure your yard slopes away from the house. This is called grading. A properly graded yard will prevent water from accumulating along the foundation during rainstorms and overwatering.

If you aren’t sure about how your yard is graded, there are several ways you can figure it out. One basic way is to tie a string to a stick and stretch it across the span. Use a level to identify when the string is even, and then all you have to do is measure the height from the ground to the string.

Drainage for Above Ground Boxes

Above ground, boxes are one of the best ways to provide optimal soil conditions and can make gardening more fun. Above ground, planters are also useful for preventing mice, squirrels, voles, and other digging rodents from eating plant roots. When you design your raised planter box, it’s vital to provide adequate drainage away from your foundation.

While there are lots of ways to create drainage, one of the best ways is also quite simple. Once the box is built, line the bottom with heavy plastic to about two inches above the bottom. Drill ¾” holes every six to eight inches just above the plastic on one long side.

When placing the planter box, make sure the holes are facing away from the foundation. This will allow excess water to drain out of the box while retaining water to encourage deep root growth.

Drainage for In-Ground Planters

If your plan is to build an in-ground planter, you will still need to address proper drainage. In-ground planting is a simple and beautiful way to add landscaping to hide ugly house foundations. Grading is even more important for in-ground planting to prevent moisture accumulation and damage to the foundation.

There are a couple of ways you can ensure proper drainage in your flower bed. The first step is to dig out the area you want to make a flower bed. Keep in mind that herbs and other small plants will need a minimum of six inches of soil, while larger vegetables and flowers will need 12 to 18 inches. Providing more depth allows plants to grow closer together and encourages vertical root growth.

Once the flower bed is dug out, a layer of gravel will help create drainage. A great method of preventing damage to your foundation from in-ground flower beds is the use of a French drain. A French drain is simply a PVC pipe with holes drilled along the length and a cap on one end. Wrapping the pipe with a window screen prevents the pipe from filling with soil.

A French drain should run several feet away from the house foundation and be buried so that the capped end is furthest from the box. The capped end should be buried deeper to allow water to flow away from the bed. Using gravel and a French drain will ensure your in-ground flower bed produces big and beautiful plants without damaging the foundation of your home.

Selecting the Correct Soil

In order for your plants to grow well, you must provide optimum soil conditions. The right soil mixture for your planter will also improve drainage, preventing water from pooling and causing damage. There are lots of different types of soil on the market, so picking the right one usually will require mixing different types of soil for the types of plants you want to grow.

You might be blessed to live in an area where the soil is perfect for growing plants. But, if that’s not the case for you, here are some ideas for getting the perfect soil mixture to create excellent drainage. Picking the correct soil mixture depends on whether you are planting in a raised bed planter box or an in-ground flower bed.

For planter boxes, you should find soil that is intended for use in raised beds. Most garden soil tends to compact too much in a raised bed, preventing drainage and forcing plants to struggle to root well. Amending the soil is also a simple process you can use to provide the optimal growing environment.

Common additions include:

  • Worm casings
  • Coffee grounds
  • Crushed egg shells
  • Compost

If you have the space to build a compost bin, your garden will thank you.

For in-ground flower beds, you will need a specific type of soil that remains light and fluffy. Like with planter boxes, you want to avoid soil that is high in clay or sand, as these tend to compact and do not provide good drainage.

The addition of perlite can significantly improve drainage and prevent soil compaction. You should also use compost, grass clippings, and shredded leaves to help provide the essential elements plants need from the soil.

Proper Watering Techniques

One of the simplest ways you can prevent damage to your foundation from planter boxes or flower beds near your foundation is proper watering methods. Today, it is affordable and easy to build an automatic watering system that uses drip irrigation and a timer. This way, your garden gets the right amount of water without the risk of forgetting the hose and flooding the box.

Using drip irrigation is a great way to prevent damage to your foundation because the water is supplied slowly, allowing your garden soil to absorb water and drain off the excess without causing soil erosion. An automatic watering system can be one of the best choices you can make for ensuring excellent production from raised bed planters or in-ground flower beds near your foundation.


Deciding to build flower beds or raised planters near your foundation quickly adds curb appeal to your home and provides an excellent way to grow your own fresh flowers, herbs, and vegetables. If you plan your garden correctly, you will never have to worry about excessive moisture causing your foundation to crack or drop.

A well-designed planter box or a garden bed can provide years of enjoyment. The secret to successful and long-term garden beds and planter boxes is proper drainage.

Not only will plants grow better when you have good drainage, but you also won’t risk causing permanent damage to your home.

5/5 - (18 votes)
Evergreen Seeds