Straw Wattles on a Graded Slope and How to Install Them

Last spring I drove past a hillside lot two days after a two inch rain and counted eleven straw wattles lying at the bottom of the slope in a pile of mud. They had been laid neatly across the face a week earlier. None had been trenched, half the stakes were missing, and the water had simply gone underneath every one of them.

Straw wattles on a graded slope are one of the cheapest erosion controls you can buy, and one of the easiest to install badly. Done right, a row of wattles slows sheet flow, drops sediment behind it, and holds the face long enough for seed to root. Done wrong, it is decoration. Here is how we size, space, trench and stake them on our jobs.

What Straw Wattles Do on a Graded Slope

A wattle, also called a fiber roll or straw log, is a tube of netting stuffed with straw, coconut fiber or wood shavings. Standard sizes are 9 or 12 inches in diameter and 20 to 25 feet long.

Wattles do not stop water. They break a long slope into short ones. On a bare 2:1 face, runoff picks up speed and cuts rills within the first storm. A wattle every 15 feet means water never gets more than 15 feet of run before it hits a barrier, slows down, and drops the soil it was carrying. That is the whole mechanism, and it only works if water cannot get under or around the roll.

Picking the Right Wattle Material

Fill	Typical life	Best for	Rough cost per 25 ft
Rice or wheat straw	1 to 2 seasons	Temporary control while seed establishes	$20 to $40
Excelsior wood fiber	1 to 2 seasons	Areas where straw seed carryover is a concern	$35 to $60
Coir (coconut fiber)	3 to 5 years	Stream banks and slow establishing slopes	$80 to $150
Compost filled sock	1 to 3 seasons	Slopes that will be seeded directly into the roll	$40 to $90

For most residential pads and cut slopes, a 9 inch straw wattle with photodegradable netting is enough. Ask for certified weed free straw if the site is near pasture or native planting, because cheap straw can seed a crop of weeds across the whole face.

Spacing Wattles by Slope Steepness

Spacing is where most installs go wrong. People lay wattles as far apart as the supply allows instead of as close as the slope needs. These are the intervals we use, measured along the slope face, not horizontally.

Steeper than 2:1: every 10 feet
2:1 to 4:1: every 15 to 20 feet
Flatter than 4:1: every 20 to 25 feet

Tighten the spacing on fine silty soils, which wash far easier than gravelly ones, and where water comes onto the slope from above. Always place one row at the top of the slope and one at the toe.

A worked example: a 2:1 cut slope with a 60 foot face and a 100 foot width needs a row at the top, rows at roughly 15, 30 and 45 feet, and one at the toe. That is five rows of 100 feet, or 20 rolls of 25 feet, plus about 130 stakes. Order two spare rolls for end turns and damage.

How to Install Wattles So Water Stays in Front

Lay them on contour

Each row must be level across the slope. A wattle that runs even slightly downhill turns into a gutter and concentrates flow at its low end, which is worse than no wattle. Snap a line with a hand level or a laser before you dig.

Trench before you set

Dig a shallow trench about a third of the roll's diameter, so 3 to 4 inches deep for a 9 inch wattle. Set the roll in, then pack the excavated soil against the uphill side. Without a trench, water finds the gap between the round roll and the ground and runs straight under.

Stake every 4 feet

Drive 1 by 1 or 2 by 2 wood stakes, 18 to 24 inches long, through the center of the roll every 4 feet, plus one within a foot of each end. Leave 2 to 3 inches of stake above the wattle. On rocky soil, pilot holes with a rebar pin save a lot of broken stakes.

Butt the ends tight and turn them up

Ends should be pushed together tightly or overlapped by 12 to 18 inches. At each row's outer edge, turn the last few feet uphill in a J shape so water cannot run around the end.

Where I Disagree With the Usual Advice

A lot of homeowner guides treat wattles as a stand alone fix: lay them across the slope and you are done. On a graded slope steeper than 3:1, I do not think wattles alone are enough, and I tell clients so.

Wattles control what happens between the rows. They do nothing for the soil surface itself. Raindrops still splash bare dirt loose, and on a fresh cut that splash erosion is a big share of the total loss. The fix is to pair wattles with surface cover: hydromulch, straw mulch, or an erosion blanket between the rows. We cover the seeding side in hydroseeding a graded slope.

The other mistake is using wattles as a perimeter barrier where a silt fence belongs. A wattle at the toe of a large disturbed area will overtop in the first big storm. For perimeter control on bigger jobs, see silt fence installation that actually holds sediment.

Checking and Maintaining Wattles After Storms

Walk every row after any rain over half an inch and at least once a week during the wet season. Look for:

Undercutting: a small channel under the roll means the trench was too shallow. Pull, re-trench and reset.
Sediment buildup: once soil reaches half the wattle's height on the uphill side, remove it or add a new row just above.
End runs: fresh rills around an end mean the J hook is missing or too short.
Loose stakes: replace any that have heaved or snapped.

Leave straw wattles in place once vegetation is established. They break down within two seasons and the netting, if photodegradable, goes with them. Coir rolls can stay for years.

Straw Wattle FAQ

How far apart should wattles be on a slope?

About every 10 feet on slopes steeper than 2:1, every 15 to 20 feet on 2:1 to 4:1 slopes, and every 20 to 25 feet on flatter ground, measured along the face.

Do straw wattles need to be buried?

Yes, partly. Set them in a trench a few inches deep and pack soil against the uphill side, or water will run underneath.

Can I plant into a wattle?

You can plant live cuttings or plugs on the uphill side, where sediment and moisture collect. Compost filled socks can be seeded directly.

The Short Version for Your Slope

Measure the slope ratio, set rows at the spacing above, trench every roll, stake every 4 feet, and turn the ends uphill. Then cover the bare soil between rows. That combination holds a graded slope through its first wet season far better than wattles alone. More ways to hold a slope are in our slope and erosion guides.