Tall Verti-Block gravity wall under construction below a wooded slope

Application guide

Gravity retaining walls without geogrid in Portland and SW Washington

Hillside lots, tight commercial pads and wet winters: what it takes to hold a slope with a gravity wall and nothing buried behind it.

4 min read
7 sections
Updated October 13, 2026

The short answer

In the Portland and Vancouver area, a Verti-Block gravity wall can hold a slope without geogrid from 5.5 ft up to 19 ft in the published design tables, depending on soil, surcharge and backslope, and up to 24.5 ft in gravelly soil with the 12-inch setback. Natrix casts the block in Vancouver, WA and drafts free preliminary designs.

Planning data, not a wall design. Every retaining wall needs a site-specific design by a licensed engineer. We draft free preliminary designs, and a licensed PE reviews and stamps the final design on approval.

Natrix Precast, licensed Verti-Block manufacturer · Vancouver, WA

Verti-Block standard unit: stone-textured face, hollow core and two cast-in lift loops — **This is Verti-Block.** One standard unit: 2 ft high, 4 ft wide, 3 ft deep, about 1,760 lb.

Meet the block

One big block, set by machine

Verti-Block is a hollow-core precast concrete block with a stone-textured face. An excavator sets each unit, raised lugs lock it to the course below, and crushed stone in the core adds weight and drains the wall from top to bottom.

Diagram of a Verti-Block unit: cast-in lift loops for machine setting, a hollow core filled with crushed stone, the stone core draining the full wall height, and raised lugs that lock into the notch under the block above

2 × 4 × 3 ftStandard unit: 8 sq ft of wall face
~1,760 lbEmpty; about 3,035 lb with stone in the cores
5.5–19 ftPublished gravity heights, no geogrid
304 sq ftWall face per truckload

Verti-Block wall with an outside corner and a curve around a lawn — Corners and curves

Verti-Block wall with stairs beside a modern home — Stairs and height steps

Stepped Verti-Block wall along a fence line — A top of wall that follows the grade

Tiered, curving Verti-Block wall on a hillside — Tiered walls

A gravity wall holds a slope with nothing but its own weight. There is no geogrid running back into the hillside, so the wall needs only the ground it sits on, which matters on the tight lots, steep driveways and commercial pads common around Portland and Vancouver.

What makes a wall a gravity wall

A gravity wall resists the soil behind it with mass and a slight lean back into the slope. Verti-Block gets its mass from large hollow-core units filled with crushed stone: a standard unit weighs about 1,760 lb empty and about 3,035 lb once its cores are filled. For taller walls, deeper mass extenders (48 to 84 in.) go in the base courses, where the push from the soil is greatest.

19 ftPublished gravity height without geogrid, gravelly soil
24.5 ftWith the 12-inch setback, gravelly soil
3–7 ftWall footprint, with no reinforced zone behind it

How tall can it go without geogrid?

The published gravity heights depend on three things: how strong the retained soil is, whether there is a load on top (a driveway, parking or a building), and whether the ground keeps sloping up behind the wall.

Published gravity wall heights, no geogrid (standard ~5° batter, mass-extender base courses)
Retained soil (friction angle)	Level, no surcharge	Level, 250 psf surcharge	2:1 sloping backfill
Silty (≥ 28°)	7.5 to 13 ft	5.5 to 11 ft	5.5 to 7.5 ft
Sandy (≥ 30°)	7.5 to 15 ft	5.5 to 11 ft	5.5 to 9.5 ft
Gravelly sand (≥ 35°)	9.5 to 17 ft	7.5 to 15 ft	9.5 to 15 ft
Gravelly (≥ 40°)	11 to 19 ft	9.5 to 17 ft	11 to 17 ft

In plain terms The soil decides more than the location does. Get a geotechnical report early: the friction angle it gives tells you which row of this table your wall lives in.

What decides the height on your site

Soil strength: the friction angle from the geotechnical report. Stronger, more granular soils push less and allow taller gravity walls.
Surcharge: a driveway, parking area or structure above the wall adds load. The tables include a 250 psf case; heavier loads are designed site by site.
Backslope: ground that keeps rising behind the wall pushes harder than level ground.
Lean: the standard batter is 2-3/16 in. per course (about 5°). Laying each course back 12 in. (about 26°) adds height without reinforcement but needs more room at the top.
Base units: mass extenders put extra weight in the base courses, inside the same narrow footprint.
Seismic: the published gravity tables don't include seismic loading. The free Verti-Block analysis software runs seismic and global-stability checks for the site-specific design.

Side-by-side wall sections: a 19 ft wall at the standard batter of about 5 degrees, and a 24.5 ft wall with a 12-inch setback per course, about 26 degrees — **Same blocks, different lean.** Published gravity heights in gravelly soil with mass extenders: 19 ft at the standard batter, 24.5 ft with the 12-inch setback.

Why the footprint matters on tight lots

A geogrid-reinforced wall needs grid layers running back into the slope, often 0.65 to 0.95 times the wall height. That zone has to be dug out and rebuilt in compacted lifts, and on many lots it runs into a property line, a neighbor's yard, a utility or a foundation. A gravity wall's footprint is essentially the block depth: 3 ft for a standard unit and up to 7 ft at the base with the deepest mass extender.

A 14 ft geogrid wall whose reinforced zone runs about 12 ft back from the face to the property line — **Same 14 ft wall, two footprints.** Illustration only: the real numbers come from the site-specific design.

A 14 ft Verti-Block gravity wall with a mass-extender base and a 3 to 7 ft footprint, leaving land back between the wall and the property line — **Same 14 ft wall, two footprints.** Illustration only: the real numbers come from the site-specific design.

Drainage in a wet climate

Every published height assumes the soil behind the wall is drained. In a region with long, wet winters, drainage is the part of the wall that does the most work. Verti-Block builds it into the section:

Wall section numbered with the four drainage details: internal stone drainage column, base collection pipe, geotextile filtration, and surface grading away from the wall

Stone-filled cores: clean crushed stone of about 1 in. forms a drain the full height of the wall.
Base pipe: perforated PVC or HDPE, 3 in. minimum, collects water at the bottom and carries it away.
Filter fabric: non-woven geotextile keeps fine soil out of the drainage stone.
Surface grading: finish grade sloped at least 2% away from the wall face.

Permits and engineering

In most jurisdictions, a retaining wall over 4 ft (measured from the bottom of the footing), or any wall holding a surcharge, needs a permit and an engineered design. Rules vary by city and county, so check with yours early. Natrix drafts a free preliminary design with block counts and a budget number, and a licensed PE reviews and stamps the final design on your approval.

Local supply

Natrix Precast casts and stocks Verti-Block in Vancouver, WA, minutes from Portland, and delivers across Washington and Oregon, with yard pickup available. Each truckload carries 304 sq ft of wall face. In our experience, lead time from the yard is days, not a season-long queue. See the numbers behind every row above in the Verti-Block design data.

Source: Verti-Crete Design Manual, Release 4.1, Verti-Block product data sheets, and Natrix Precast project experience (marked "in our experience").

In the field

Builder / Subdivision · Long gravity wall along a property line

Green Mountain

A long Verti-Block wall that turned an eroding slope into a clean, flat edge along the lot line, with a fence set just behind the top course.

View project →

Residential · Hillside walls with integrated stairs

RC Residence

Upper and lower Verti-Block walls below a modern hillside home, with stairs built into the wall face so the whole slope is usable.

View project →

FAQ

Common questions

How tall can a retaining wall be without geogrid in the Portland area?

It depends on the soil, not the city. Verti-Block's published gravity tables show 5.5 ft to 19 ft without geogrid at the standard 5° batter with mass-extender base courses, and up to 24.5 ft in gravelly soil with the 12-inch setback. A geotechnical report gives the soil strength the design uses.

Do I need a permit for a retaining wall in the Portland area?

In most jurisdictions, walls over 4 ft (measured from the bottom of the footing), or any wall holding up a surcharge like a driveway, need a permit and an engineered design. Check with your city or county. Natrix drafts a free preliminary design, and a licensed PE stamps the final design on approval.

Where is Verti-Block made for Portland projects?

Natrix Precast casts and stocks Verti-Block in Vancouver, WA, just north of Portland, and delivers across Washington and Oregon. Yard pickup is also available.

Is a gravity wall cheaper than a geogrid wall?

Often, on tight sites. A gravity wall skips excavating, rebuilding and compacting a reinforced zone behind the wall, which can run 0.65 to 0.95 times the wall height. Which costs less depends on the site, so our free preliminary designs show the gravity option and, where needed, the geogrid option.

How does a gravity wall handle heavy rain?

Through drainage built into the wall. Crushed stone in Verti-Block's hollow cores forms a drain the full height of the wall, a perforated pipe collects water at the base, filter fabric keeps fines out, and the finish grade slopes away from the face.

Get a free preliminary wall design.

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