Quick Answer
A standard 4x8 raised bed at 12 inches deep needs about 1.2 cubic yards of loam-compost mix — round up to 1.5 yards on a single bed, or 2 yards if you're filling two beds. Order screened loam (not unscreened topsoil), specify a Watertown drop spot the truck can reach, lay a 10x10 tarp on the driveway before delivery, and have a wheelbarrow plus a flat shovel ready. Most Watertown bed builds finish the same afternoon the loam lands.
Step 1 — Measure the Bed and Do the Yardage Math
Yardage is the easy part. A cubic yard is 27 cubic feet. Here is the standard Watertown raised-bed math:
- 4x8 bed at 12" deep: 4 × 8 × 1 = 32 cu ft ÷ 27 = 1.18 cu yd — order 1.5
- 4x8 bed at 18" deep: 4 × 8 × 1.5 = 48 cu ft ÷ 27 = 1.78 cu yd — order 2
- 3x6 bed at 12" deep: 3 × 6 × 1 = 18 cu ft ÷ 27 = 0.67 cu yd — order 1
- Two 4x8 beds at 12" deep: round up to 2.5 cu yd
Always round up. Loam settles 10–15% in the first three weeks once you water it, and you'll want a half-wheelbarrow in reserve to top off after the first heavy rain. Browse Raised Garden Bed Materials for the per-yard rates.
Step 2 — Pick Screened Loam, Not Unscreened Topsoil
For raised beds, screened loam is the only right answer. Unscreened topsoil shows up with stones, root chunks, and sometimes a piece of asphalt — fine for grading a slope, ruinous for a vegetable bed. Screened loam runs through a half-inch screen so you get even texture down to the carrot root.
Ottr's screened loam is a loam-compost-sand blend that drains well in a Watertown clay-heavy yard but holds moisture during a July dry spell. For a deeper walkthrough of what's actually in the pile, see the Ottr Screened Loam review — same product, same screening size as what arrives at any Watertown driveway.
Step 3 — Pick the Drop Spot Before You Call
Watertown lots are tight. Common Pleasant Street and Mount Auburn driveways have street trees, low utility lines, and fence posts the dump-truck driver has to navigate. Walk the route from the curb to where the pile will sit and confirm:
- 8 feet of overhead clearance for the dump bed to raise
- 10x10 minimum flat ground for the pile
- The driver can back in straight — no parked cars, no trash bins
- The pile is within wheelbarrow distance of the bed, ideally under 60 feet
If the bed is in the back yard with a 36" gate and no truck access, the loam still goes on the driveway. You and a wheelbarrow do the rest.
Step 4 — Tarp the Driveway Before Delivery
Loam stains concrete and asphalt for a season. Lay a 10x10 builder's tarp on the drop spot before the truck arrives. The driver dumps onto the tarp, and when you finish moving the loam, you fold the tarp and shake the residue into the bed. Driveway looks the same as it did Friday.
Step 5 — Place the Order With the Right Detail
When you call Ottr to order, have these five items ready:
- Yardage (1.5 cu yd, etc.)
- Product (screened loam — not unscreened topsoil, not garden mix)
- Watertown delivery address with cross-street
- Drop spot description ("driveway, left side, on tarp")
- Delivery window ("Saturday morning, anytime before noon")
Most Watertown deliveries land within a 2-hour window. The driver calls 30 minutes out. For an end-to-end walkthrough on building the bed itself in cedar before the loam shows up, the cedar raised beds Cambridge guide has the cut list. For layering the loam, compost, and mulch correctly once it lands, see How to Layer a Somerville Raised Bed.
Step 6 — Move the Loam Same Day If You Can
Loam left piled on a tarp through a wet week compacts and starts losing structure. Move it into the bed within 48 hours. A 1.5-yard pile takes one person about 90 minutes with a wheelbarrow and a flat shovel. Two people, 45 minutes.
For best establishment of the vegetables that follow, the UMass Extension recommends a final layer of compost worked into the top 4 inches before planting. The US Composting Council has the standards on what "finished" compost actually means — worth a read before you mix.
Watertown has the soil — you just need to point it at the right bed.
