How to Build a Raised Garden Bed: Soil Guide for Western Washington
Raised beds succeed or fail based on what you fill them with. Native Kitsap County soil — typically heavy clay — doesn't belong in a raised bed. But neither does pure potting mix for anything larger than a small planter; it's too expensive and dries out too fast in a large volume. The answer is a blended approach, and the formula below has worked for Western Washington gardens for decades.
Why Native Kitsap Soil Doesn't Work in Raised Beds
The native soil in Gig Harbor and surrounding Kitsap County is clay-heavy. In the ground, this can be managed — you work in amendments over time, improve drainage gradually, build organic matter. In a raised bed, it's a real problem:
- Clay compacts tightly in the contained environment, strangling roots
- Poor drainage leads to root rot, especially in our wet winters
- Soil structure breaks down as you work it over multiple seasons
Starting a raised bed with native clay is starting with a handicap you'll spend years trying to fix.
The Western Washington Raised Bed Formula
The classic raised bed mix — adapted for Pacific Northwest conditions:
- 60% quality topsoil — the base structure and body of the bed
- 30% compost — organic matter, nutrients, microbial life
- 10% coarse sand or perlite — drainage, prevents compaction over time
Harbor Soils' 3-Way Topsoil Mix is pre-blended for this application — quality topsoil, compost, and soil amendments combined in one product. You order one material, it arrives mixed and ready to use. For most raised bed projects, this is the simplest approach.
3-Way Topsoil Mix vs. Garden Mix — Which Is Better for Vegetables?
Both work well for raised beds. The choice depends on what you're growing:
3-Way Topsoil Mix: Great all-purpose choice for ornamental beds, general vegetable gardens, and larger or deeper beds where filling volume matters. The blend is solid for most plants.
Garden Mix with Fish Compost: Richer, with higher organic matter and nitrogen from the fish compost. Better for intensive vegetable growing, especially tomatoes, squash, and leafy greens. More expensive per yard but produces noticeably better yields in vegetable beds.
Many Western Washington gardeners use a 50/50 blend: 3-Way Topsoil Mix as the base, topped or mixed with Garden Mix with Fish Compost for the upper 4–6 inches where roots actively grow.
How Much Soil Do You Need?
Use this formula:
Length (ft) × Width (ft) × Depth (inches ÷ 12) ÷ 27 = cubic yards
Common raised bed sizes:
- 4×4 bed, 12 inches deep: ~0.6 cubic yards
- 4×8 bed, 12 inches deep: ~1.2 cubic yards
- 4×12 bed, 12 inches deep: ~1.78 cubic yards
- Two 4×8 beds, 12 inches deep: ~2.4 cubic yards
For beds less than 1 cubic yard, bagged soil may be practical. For anything larger, bulk delivery costs significantly less per cubic yard and saves many trips from the hardware store.
Tips for First-Time Raised Bed Builders
Go 12 inches deep minimum for vegetables. Roots — especially for tomatoes, squash, and root vegetables — need room. A 6-inch deep bed will work but you'll notice the difference in productivity.
Don't use straight compost. Pure compost is too nutrient-dense for seeds and seedlings, and it can dry out quickly. Mix it into your base soil rather than using it alone.
Leave 2 inches at the top. Filling a bed all the way to the top looks full but means you can't water without washing soil over the edge. Leave space for watering and adding mulch.
Mulch the surface. A thin layer of bark or compost on the bed surface retains moisture and suppresses weeds — especially important in the dry Kitsap summer months after the spring rains stop.
Delivery to Your Gig Harbor Project
Harbor Soils delivers bulk topsoil, garden mix, and compost throughout Gig Harbor, Port Orchard, Fox Island, Key Center, and surrounding Kitsap County. Same-day delivery available. No minimums — order exactly what your beds require.
Call 253-857-5125 with your bed dimensions and we'll help you calculate exactly what to order.