Is Mulch or Gravel Best to Put Under a Stairs or Deck?

Gravel

• If the area under your deck or stairs will collect water or is prone to gathering moisture, an inorganic mulch such as gravel, crushed rocks or river rocks is best. Gravel is a good material to place under outdoor structures, because it allows water to drain and doesn't decompose. A thick layer of gravel, if piled around the support beams of your outdoor structure, can also help to make the structure more stable.

Other Inorganic Mulches

• There are other mulch products that won't decompose and will allow for drainage. Inorganic mulches include shredded rubber, crushed recycled glass, plastic mulch and fabric mulch. These types of inorganic mulches will inhibit weed growth and help control erosion. However, some inorganic mulches such as recycled rubber can leach chemicals into the soil.

Cedar Mulch

• Cedar mulch is made from chips and shredded bark from the cedar tree. Mulch made from cedar trees usually has a reddish color and a pleasant scent, but it will decompose and need to be replaced once every couple of years. Cedar mulch can be a good choice, because the scent of cedar repels garden pests like fleas.

Other Organic Mulches

• Organic mulches come in many varieties. Hardwood mulch is made from chips, shavings and bark from trees that are considered hardwoods such as oak and maple. Other types of wood mulch include cedar mulch, pine needles and coconut hulls. These organic mulches can, however, decompose and need to be replaced over time, and mold can grow if the site doesn't have drainage. Organic mulches are good to spread under a deck or stairs if you're considering planting in the soil at a later time, because they put nutrients back into the soil.