Back Button

Do You Lay a Tarp or Remove Grass When Building a Deck?

Samantha Volz

When attaching a deck to your home, whether at the front or back of your house, there are important preparatory steps you need to take. Most decks are elevated off the ground, so the space underneath us a concern. What you do with that space contributes to the your deck construction's success or failure.

Drainage Issues

The space underneath a deck needs to drain excess water.

The biggest issue contributing to decking success or failure is drainage. No matter what decking material is used, rainwater seep through to the area below. This rainwater needs to drain away from your home and your deck. Standing water attracts insects and bacteria and also gradually erodes the soil supporting the deck's beams or the support structures themselves if the deck is made of wood.

Grass Problems

Removing the soil or grass from below your deck may seem a good idea, but this leads to drainage problems. Removing grass, topsoil and sod exposes the underlying dirt, which is often compacted and drains slowly. These underlying areas also often contain large stones or buried tree roots, which slow the drainage of water. Leaving the grass in place facilitates drainage. The grass may eventually die off due to lack of sunlight filtering through the deck, but the remaining topsoil still drains water faster than if you dug out the entire area.

Tarp Options

Laying tarp during deck construction is unnecessary unless you are protecting the grass below the deck during construction and intend to remove it later for easier cleanup. A tarp spread under a deck is a breeding ground for insects and bacteria, since rainwater gathers on the tarp and never properly drains. Even evaporation is slower, since the area is not exposed to sunlight. If you want a tarp for a decorative look, such as a support for decorative stones or blocks, use landscaping fabric, which is porous and allows water to drain through easily.

Soil Level Decking

If you are installing a fixture that is level with your home and the soil, such as a patio, remove grass and lay tarp for the project. The reason is that the material you use for this patio, whether it be treated lumber or pavers, needs a sturdy and level support. This project involves digging out the area to a depth of 6 to 8 inches and covering it with landscape fabric facilitating drainage. Paving base or gravel, as well as sand, level the area for a safe, firm and flat construction.