Mulch and beds along the foundation

The beds along a house sit on the ground that most needs to shed water. Soil there should fall away from the wall. Mulch piled against the foundation holds moisture right where termites and other pests look for a way in. Subterranean termites cause about $5 billion in structural damage a year in the United States. Termites foraging in mulch on treated soil can use it as a bridge over the termiticide barrier to reach the house.

Any mulch can draw pests. Wood mulches hold moisture and warmth underneath, and gravel has drawn more termites than pine bark, hardwood or eucalyptus mulch in studies. Inorganic mulch is the better choice next to a foundation, gravel possibly excepted.

What you need

• A rake and a flat shovel
• A 4-foot level and a straight board as long as the bed is deep
• Soil to fill low spots, if the bed tips toward the house
• Bark or wood mulch, about 1 cubic yard for every 110 to 160 square feet at 2 to 3 inches deep
• Edging to hold the mulch and soil in the bed

Steps

1. 1

   Pull the old mulch back from the wall

   Rake it out toward the lawn so you can see the soil and the bottom of the foundation.

   15 min

2. 2

   Check the slope of the bed

   Lay the board from the wall out across the bed with the level on top. The soil should fall at least half an inch for every foot out from the house.

   10 min

3. 3

   Fill and tamp any spot that tips toward the house

   Add soil until it falls away from the wall, then tamp it down so it doesn't settle back. Keep at least 8 inches between the soil and the bottom of the siding.

   30 min

4. 4

   Clear a 6-inch strip along the foundation

   Leave at least 6 inches of bare ground between the mulch and the wall. A termite inspector needs to see the concrete at ground level to spot the mud tubes termites build up a foundation.

   15 min

5. 5

   Spread the mulch 2 to 3 inches deep

   Mulch deeper than that cuts the air to the soil, can stay waterlogged after rain and gives mice, voles and insects shelter over winter.

   30 min

6. 6

   Leave a gap at each trunk and stem

   Keep the mulch 2 to 3 inches away from the base of each tree and shrub.

   10 min

7. 7

   Set the edging

   Run it along the outer edge of the bed so the mulch and soil stay in the bed.

   20 min

8. 8

   Check the bed in the next rain

   Water should run out across the bed and away from the wall, with no puddle along the foundation.

   5 min

Choosing the mulch

Mulch in a bed holds down weeds, keeps the soil moist and evens out its temperature. It also lets more rain soak in and cuts injury to trees and shrubs.

• Organic mulch is bark, wood chips, pine straw, leaves, straw or shredded paper. It feeds the soil as it decays and needs replacing over time.
• Inorganic mulch is crushed stone, gravel, landscape fabric, plastic sheeting or tire chips. It doesn't break down, so it doesn't need topping up, and it adds nothing to the soil.
• Cedar is avoided by Argentine ants and odorous house ants for nesting.
• Melaleuca mulch isn't eaten by the eastern subterranean termite.

Of the common mulches, pea gravel has the fewest insects and other small animals living in it, and hardwood and recycled wood have the most. Bagged mulch comes with fungi and bacteria already growing in it, so insects settle into a new bed quickly.

Keeping it right

Mulch that sits undisturbed lets insects settle in, so rake or turn it over now and then. Bark and wood mulch break down and add nutrients to the soil, so they need topping up as they thin. Keep the total at 2 to 3 inches rather than adding a full new layer over the old one each spring.

Downspouts that empty into a foundation bed undo the slope. Each one should carry water at least 5 feet out from the foundation onto ground that falls away. Fixing water that pools in the yard covers downspouts, grading and drains.