Why You Need Underlayment for Your Pond

Chairs on pond

Ponds bring a refreshing atmosphere to a place. How can you ensure the longevity of a pond and make it more durable. Let’s find out.

First, you need to put an underlayment to protect the pond liner. Pond liners are susceptible to damages caused by rocks or other sharp objects that can puncture the liner and cause the water to leak. A pond’s underlayment can also shield the liner from rodents and prevent roots from growing into plants out of the soil.

In this article, we will discuss what pond underlayment is, why you need it, the things you can use as underlayment, and how to install it.

Click here to read our complete pond guide.


What Is Pond Underlayment?

Pond underlayment is a fabric used to protect the liner from damages caused by the rocks on the ground. There are several options of underlayment if you want to save money, including old carpets, newspapers, and many others.

Underlayment is different from a liner as it is first set on the surface of the ground, and is then followed by the liner. It will serve as a cushion that separates the sharp rocks from the liners. Pond liners are vulnerable to puncture, and thus, need a barrier from the ground.

The fabric of the underlayment is a non-woven material. It is not the fabric usually used to make apparel as it doesn’t contain grains nor bias. It is made of polypropylene material, which can withstand heat but is also prone to ultraviolet degradation.


Why Should You Use Pond Underlayment?

Underlayment acts as the shield of your pond liner, but its purpose doesn’t stop there. Something else you should know about the importance of underlayment is that it prevents the stretching of the liner. For example, if you use a rubber pond liner without the support of underlayment underneath it, the water pressure will force to stretch the vulnerable areas of the liner.

Rubber pond liners are stretchable and can perfectly follow the shape of the pond you dug. Even though this kind of liner looks durable, it sometimes won’t resist too much stretching, which will result in a tear and a hole in the liner.

Other reasons why you need to use pond underlayment include the following:

  • Cushioning

When digging a hole for a pond, you must remove the rocks and other pointy objects on its surface. This will help prevent punctures on the liner even though, since there is an underlayment, you don’t have to worry about it. Underlayment is indeed known for lasting for years, which is a great advantage.

  • It protects pond liner from rodents

In case you wondered how strong your pond underlayment is, it is durable. Without it, pond liners are prone to tear and damages caused by rodents on the ground. That will result in leakages of the water from the pond, which will destroy the whole pond.

Rodents are known to dig under the ground for safety. If they poke holes under the ground and find a way to make a tunnel heading toward the pond, they will likely prick the liner.

  • It settles the liner’s position

Apart from stretching, pond liners are inclined to move due to the ground’s motions. Since the movements of the ground are due to natural causes, you must find a way to prevent your liner from moving. That is where the underlayment comes in.

It is essential and fits the shape of the hole for a pond. If you place the liner on top of it, you can guarantee it will hold its position.

  • It increases durability

Since underlayment is made of synthetic materials, you can be rest assured it will last a long time. The only problem you need to keep in mind is its exposure to too much heat. Although it can resist it, it might give in and get damaged if constantly exposed.

In terms of deterioration, you can trust the durability and longevity of underlayment. It was created to protect the liner, so it is incredibly sturdy to hamper rocks and other damaging elements on the ground.

  • It prevents root growth damages

Some plants may unexpectedly grow from the soil. The development of roots can provide a strong foundation of the plant, which can penetrate the pond liner and tear it. To prevent this from happening, laying an underlayment is a good countermeasure.

With an underlayment, the root growth is hampered, which won’t cause it to develop and damage the liner. Since you can’t replace a pond liner once damaged, you must ensure there is support coming from the underlayment.


Things You Can Use as Pond Underlayment

Although underlayment is sold in stores, you could also find some alternatives at your home. The ideal materials for pond underlayment are carpets, weed barriers, newspapers, geotextiles, and sand. Some of these may require another layer of underlayment as it has inefficient qualities.

Before you use a certain material as a pond underlayment, keep in mind that you need to consider a few things. We have compiled the following materials and their pros and cons.

  • Geotextiles

Geotextiles are used to divide layer materials, especially on the surface of the soil. This type of sheet is permeable and capable of draining. This material is used as a preventive measure from the grounds, like landfill sites.

Geotextiles are made of polypropylene or polyester. They are particularly used to ensure the solidity and stability of the soil’s surface. They can also manage solid erosion, which is a good foundation to prevent the shift of pond liner whenever there are weather changes.

  • Weed barriers

Since weed barriers are geotextiles, they are produced using polypropylene or polyester. This kind of material has the same qualities as geotextiles but is created for weeds. It is used to spread on the ground to hamper the weeds and allow proper water access to the surface of the soil.

If you don’t want to spend on a new underlayment, you can use a weed barrier as an alternative. Just make sure the material you are going to use has no holes or punctures because its purpose is to protect the lines from the ground surface.

  • Carpets

Another way to save money from buying new underlayment is to use an old carpet. Keep in mind that the carpet you are going to use should be made of polypropylene. Several materials are used to make carpets, including wool, which tends to decay.

Thus, before you use the old carpet you have at home, make sure you know what materials were used to make it. Ask the manufacturer or seller to ensure the underlayment will be efficient. If a wool carpet rots, the pond liner is vulnerable to dangers or damages.

Some polypropylene carpets have a mix of different materials. This kind of carpet is susceptible to magnet bacteria, resulting in a bad smell that could attract rodents and can tear them.

  • Newspapers

You can also use old newspapers that have been stored in your shed for a long time as an underlayment for your pond liner. Before you lay down your pond liner, cover the ground with at least half an inch thick layer of newspapers.

Newspapers are prone to decomposition. The difference between newspapers and common paper is newspapers’ ability to become clay when wet. Meaning that if this material stays under the pond for a long time, it will harden and protect the liner.

  • Sand

Sand is a good option for the first layer of underlayment. Sand has qualities that may not work as an efficient underlayment alone. When you first set sand on the ground of the hole you dug, you should place a geotextile underlayment on top of it.

Sand can fill the spaces or gaps of the ground you dug. You can flatten the hollows by covering them with sand and smoothen the surface. Since sand has loose attributes, it can move to different places or positions over time.


How to Install Pond Underlayment

Now that you know underlayment and its different types, you can start installing some in your pond. However, plan everything first, from the design to the materials, the space you are eyeing, and the underlayment you are going to use. Don’t forget to remove the stones and sharp objects after you’ve dug the hole for the pond, so you can ensure it won’t damage the pond’s liner.

  1. Plan the location of the pond

Before anything else, determine where you want to put your pond. Choose a spot where your pond could beautify your place. Note not to pick the area where it can cause limited space in your yard.

You also need some equipment to operate your pond. For instance, in your blueprint, include where you want to put the pipes. You can consult an expert to help you plan the pond if you hesitate to do it on your own. Doing so can ensure the work will flow smoothly and the structure will be successful.

  1. Dig a hole

After the plan, dig the ground for the pond. Don’t immediately put your underlayment and liners without the holes for the pipes and fittings. That would force you to repeat the process all over again if you forgot to include it in the preparation.

  1. Remove sharp objects

Double-check the ground once you’ve dug the hole. Ensure you removed all of the sharp objects, like rocks or other materials that are exposed to the surface. This can guarantee you can prevent damages to the liners.

Avoid being complacent due to the purpose of underlayment. Sharp rocks can create a hollow to the underlayment and may inflict damages to the liner on top of it. You can also put a first layer of underlayment, like soil, to flatten the terrain.

  1. Lay down the underlayment

The standard size for a geotextile underlayment sheet is 4 or 5 x 100 m. If your pond is wider than the sheet of geotextile you bought, you should attach two or more sheets depending on the size of your pond. Make sure the hole you dug is fully covered. It would also be best to have extensions overlapping on the ground, on top of the hole.

To connect the geotextile sheets, you can apply heat and melt them. Attach the melted part to the other sheet and put a bit of pressure on it so it will stick together. Avoid using staples or putting holes to tie it together as it can hamper the protection of the liner. The holes allow sharp objects to break into and will damage the liner.

  1. Lay the pond’s liner

When laying the pond’s liner, spread it on top of the hole first. Make sure you’ve installed the underlayment before the pond liner. After spreading it, press the liner to follow the shape of the pond’s hole. As with underlayment, we recommend you have an extension that overlaps the edges of the pond’s hole. You can cut the extra underlayment after you’ve set up all of the materials you need to install for the pond.



Ponds are a good option to build for the aesthetic of your yard. The water structure requires the proper installation of the materials so it can operate for a long time. Underlayment is essential to protect the upper parts of the pond. Without it on the ground of your pond, the liner may not last long as it will be exposed to the dangers underneath it.

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