Building an elevated bed against a house is useful for planting flowers, fruits, vegetables, and other different types of plants. It can save huge space in your garden and normally built-in corners.
Garden soil can cause a house to become weak due to moisture and root ingression into the foundation. Building a garden bed against a house can be done safely by using a barrier placed between the soil and the wall. An added layer of protection can be used by building the garden bed 12 to 24 inches away from the house.
When it comes to constructing anything foreign close to a house good planning is crucial to prevent damage to your house.
Building a raised bed against a house is not a common practice and there are a few things to consider before you start laying down your gran plan.
These are –
- Protecting the house against Water
- Protecting the house against roots and pests
- Light exposure for the Plants
Related articles you may find helpful –
Termites in raised bed garden
How to protect a brick wall against soil and moisture
Why do tree roots cause concrete to crack
How to Build a Raised bed Against a House
Following steps must be followed to build a raised garden against your house:
1. Dig down into the soil
Deeply dig the ground (almost 10-20 inches deep) for the construction of a bed. Compact the surface soil with the help of a heavy log and level the surface using a level meter for good drainage.
2. Cast bricks around the excavated area
Construct a framework of the raised bed with bricks so finished front and back part of an excavated area with cement blocks or bricks.
3. Line a layer of bricks as a veneer in front of the house wall
You can join the bricks to the wall or line another layer in front of or parallel to the existing wall.
4. Install waterproof barrier
Now install a waterproof thick plastic sheet or cotton fabric to make the barrier between the wall and bed.
5. Line the Bottom of the Raised Bed Garden
Line the bottom of a garden with organic material which would add nutrients to the soil as it is being broken down. This is also done to help fill the garden bed without having to add a lot of nutrient rich soil which will increase the cost of the project.
6. Add Filler
This can be any kind of organic material such as tree barks, logs, wood chips, hay or even old soil from a previous garden.
7. Add soil
Add a layer of soil mixed with nutrients and organic fertilizer on top of the organic material.
8. Add plants
Now the bed is ready for different plants such as flowers, fruits, veggies, or mixed ones.
The Downside of having a raised bed against a house
When you want to design your garden rooftop or courtyard through raised beds beware their demerits before construction:
1. Lack of sunlight
One thing to consider when building a raised bed against a house is sunlight. If the wall is south facing then you would not have much problem.
In the northern hemisphere the sun will provide almost 12 hours of full sunlight during the daylight hours which is beneficial to the plants that are on the southern side of a wall structure.
However, if the wall is eastern or western facing then the amount of sunlight that the plants will receive will be limited. This will affect the overall production of crops during the growing season (beginning of spring to the end of fall)
2. Waterlogging and Salinity problems
Over the course of time if a barrier isnt used to protect the house structure from moisture, the walls will begin to absorb water and weaken.
This in turn will lead to cracks if any pressure is placed on the house foundation by the natural movement of soil.
3. Promotes pests and insects
Having soil against a house, in this case, the walls of a house can bring unwanted pests into your home.
Termites are subterranean insects which thrive in moist and dark conditions. Termites get nutrients from cellulose, an organic fiber found in wood and plant matter.
This means that they can eat into any wooden structure in your home and can easily make any home unlivable by weakening its structure.
Waterproofing to protect the foundation of the House
The foundation of the house must be protected from underground and outside water seepage.
To make sure that water does not enter the wall’s foundations you should use a waterproofing system.
There are several methods you can use to prevent moisture ingress into a wall’s foundation.
Here we have listed the more popular methods –
Heavy polyurethane coating
This coating is a synthetic coating and is usually two to three times thicker than normal coatings.
The purpose of the coating is to prevent moisture ingression from the outer walls into the inner parts where it can cause stresses and cracks over time.
Penetrating sealers work by increasing surface tension on the concrete.
These products will create hydrophobic water-shedding, meaning water will quickly be repelled from the sealed concrete surface instead of soaking in.
Fiber Cement Board – Prevent water ingress
Fiber cement board is one of the better choices of building materials that work on home exteriors to prevent moisture from ingressing into the house’s foundation.
The pores in the concrete fiber are too small for water molecules to ingress and cause a problem.
Epoxy for Walls
Epoxy acts as a protective and decorative paint to prevent moisture ingress on cement-based substrates, such as concrete, plaster, cement-mortar, and cement boards.
Using a pool liner before the addition of soil and other substrates on a garden bed can help prevent water from going in the wrong direction.
Bitumen paint acts in a similar manner to epoxy, which coats and protects the walls surface against the negative effects the bare dirt can have on a wall.
It is very cheap, readily available and can be easily applied using a paintbrush.
Preventing Root Damage Using a Tree Root Barrier –
A tree root barrier will not directly protect the wall from soil.
What it actually does is prevent roots from trees and plants from venturing close to your home by posing a hard barrier to prevent growth in unwanted directions.
Roots can cause cracks to concrete structure and house foundations by absorbing moisture causing the soil to subside beneath the foundation. A void is created which removes the support from under the foundation causing stress and unwanted cracks.
Additionally the roots themselves can place additional pressure on the foundation and walls as they grow bigger which also causes stress and cracks.
Benefits of using a barrier lining during construction
A barrier lining is very useful in the construction of raised bed gardens and will help protect walls and other foundations from the effects of having plants closeby.
- A lining can protect close-by walls from wandering roots.
- It can also maintain run-off water in the soil.
- Keeps the soil protected from weeds and pests such as termites.
Keeps Roots at Bay
Roots can cause cracks to concrete structure and house foundations by absorbing moisture causing the soil to subside beneath the foundation.
A void is created which removes the support from under the foundation causing stress and unwanted cracks.
Promotes Water Runoff
Raised bed gardens are constructed so that it utilizes amended soil for the efficient growth of plants and vegetables.
This soil would therefore have properties that would
- provide good nutrients to the plants
- aeration for plant roots
- Good drainage
Protection from weeds and pests
A lining barrier would prevent weeds from the existing soil from infiltrating into the nutrient rich soil that is intended for your plants.
If they are allowed to do so they can rob your plants of nutrients by competing for space within the raised bed.
Additionally, pests like termites are naturally found in untreated soil and can also easily infiltrate into the amended soil mixture.
Termites in your raised bed can cause problems if you are using wood as the siding material and they can easily eat through hence weakening the raised bed structure. As a result, the wood would break with very little pressure.
Will the Soil Affect the House?
Yes! The soil will affect the house because as the soil sits against the brick and mortar structure, the moisture from the soil will slowly start penetrating into the house.
Over the course of time, the wall structure will weaken from routine watering of the plants in the raised bed.
It can also provide passage to underground soil termites and insects to enter the house, so it will never be a good idea to simply place soil against any wall structure without the proper protection in place.
Should you Join the Garden Bed to a House?
Garden beds can be joined to a house. However, over time, if bricks are used as the siding material, it can come loose from the house wall because it was not part of the initial structure when the wall was being built.
To prevent any soil from washing away when this happens you can line the raised garden bed with a protective liner as previously explained.
Many homeowners when they have bought their new homes and have inherited previously owned garden beds and are faced with this same problem.
The parts of the garden bed which joins the wall, just separates.
What you can do to fix the issue which may seem a crack is to fill it. A simple mortar filler mix will do the trick.
Can Roots Cause Damage to the House?
Plant roots can damage the housel by:
- Causing stress and cracks in the house foundation
- Absorb underground water and spread moisture to the wall bricks
When roots absorb water, the moisture level is lowered, resulting in shrinkage of the soil. This shrinkage causes movement of underground soil, and the foundation is disturbed.
The same happens when water is lost during transpiration, and pressure is developed on the walls by the roots that will cause cracks to concrete.
For this reason, it is also recommended that raised bed gardens be constructed 1 to 2 feet away from a house so that the walls would not be affected by the roots from the garden.
How to Stop Roots in an existing garden
If you want to prevent root problems in your existing raised bed, you will have to install obstacles to stop spreading plant roots in raised beds.
Or you can simply dig a 1-ft deep channel around the outer limits of the raised bed and compress the soil at the bottom to compact it and make it more difficult for the occupying roots to grow.
To stop roots from becoming a problem in the garden you can use Herbicides applied directly to the soil surface that are carried down into the root system with rainfall or watering.
The chemicals kill the roots when they come into direct contact with them. Chemicals that work in this way include bromacil, hexazinone and tebuthiuron.
Raised bed gardens are eco-friendly and sustainable.
They enhance the scenic beauty of the home while at the same time, utilizing very little space.
In order to have a garden bed against a house you have to put in place the necessary protection so the soil would not compromise the strength of your home’s structure..