Concrete Patio Design and Planning: Layout, Size, Drainage, and Finishes
Last Updated:The patios that get used most are planned around how people actually use the space: where the table goes, where the grill smokes, which corner gets afternoon sun, and where the water runs when it rains. Design decisions are cheap on paper and expensive once concrete is poured, so this guide covers the planning stage: sizing, layout and shape, slope and drainage, finishes by use, and how to work with Seattle's shade and rain. When the plan is ready, our concrete patio installation page explains how a project gets scoped. For budgets, see the concrete patio cost guide.
Start with use and size
Measure your furniture before you pick a size. A good rule of thumb is to allow about 3 feet of clear space around a dining table so chairs can pull out, and a clear walking path of about 3 to 4 feet past seating areas. The sizes below are planning starting points, not rules.
| Use | Planning starting point | Notes |
|---|---|---|
| Bistro table for two | About 8 x 8 ft | Fits a small table plus chair clearance |
| Dining for 6 to 8 | About 12 x 14 ft or larger | Measure table length plus 3 ft on every side |
| Lounge seating | About 12 x 12 ft | Sofas and chairs take more depth than they appear to |
| Grill or outdoor kitchen | Add a zone of roughly 5 x 8 ft | Keep it away from siding, windows, and eaves, and follow the grill maker's clearances |
| Fire pit | Circle about 12 to 16 ft across | Check local fire rules and the manufacturer's spacing |
Combined uses add up quickly. Dining, lounging, and a grill together often need two zones, joined by a wider walkway or separated by a step.
Layout, shape, steps, and walls
- Connect to the door you use most. A patio that starts at the kitchen or slider gets used. One at the back of the lot often doesn't.
- Rectangles are the most economical to form and joint, and they suit furniture.
- Curves and free-form edges soften a yard and follow planting beds, but they take more forming time and need careful joint layout so cracks stay in the joints.
- Multi-level patios work well on sloped Seattle lots. Separate dining and lounge areas with a step instead of building one large, heavily graded slab.
Plan steps and walls with the patio, not after it. Steps from a door to a patio need consistent riser heights. Seat walls can double as a grade break, and a low retaining wall can create a flat area on a slope. SDCI lists some retaining walls not over 4 feet tall, measured from the bottom of the footing, among work that usually doesn't need a permit. Taller walls, and any wall on an environmentally critical area, need a closer look. See our concrete steps and retaining wall pages for those elements.
Slope and drainage away from the house
Every patio needs to drain, and the direction matters more than the amount. Water should move away from the foundation, never toward a door or basement wall.
- Set the slope. Most designers plan about 1/8 to 1/4 inch of fall per foot, roughly 1 to 2 percent, away from the house. That is enough to shed water without furniture feeling tilted.
- Mind the door threshold. Keep the slab surface below the door sill so rain and snowmelt can't run under it.
- Decide where water goes. Send it to lawn, a planting bed, or a drain, not onto a neighbor's lot or back toward the house.
- Add a drain where slope can't do the job. A channel drain along the house edge or a French drain at the low side helps on flat or enclosed yards.
- Handle the downspouts. Don't let roof water dump onto the slab or under its edge, where it can wash out the base.
Large patios add hard surface, and Seattle's stormwater rules can come into play. Read Seattle stormwater rules for driveways and patios before finalizing a big layout.
Finishes by use
| Area | Finish that tends to work | Why |
|---|---|---|
| Uncovered walking paths and steps | Broom or exposed aggregate | Texture for grip when wet |
| Dining area | Stamped or lightly textured, sealed | Looks finished; sealer resists food and grease stains |
| Grill zone | Broom or exposed aggregate, sealed | Hides grease spots and keeps traction |
| Covered patio | Stained, integral color, or smoother finishes | Stays drier, so slip risk and moss are lower |
| Shaded, north-facing spots | Exposed aggregate or broom | Moss and algae are easier to manage on coarse texture |
For a side-by-side comparison of traction, upkeep, and cost tier, see our decorative concrete finish comparison.
Sun, shade, and Seattle's climate
Watch your yard through a full day before choosing a location. South- and west-facing patios get the most use in Seattle's short summers and dry fastest after rain. North-facing spots under trees stay damp, grow moss, and collect needles and leaves. If shade is unavoidable, plan for a coarser finish, a sealer, and easy cleaning access. Our guide to moss and mildew on Seattle concrete explains why.
A roof or pergola over part of the patio extends the season through spring and fall rain. If you might add one later, plan for its footings now, since cutting into a new slab for posts costs more than forming footings at the start. To turn the plan into a quote, call Seattle Concrete at (206) 552-9998.
Frequently asked questions
How big should a concrete patio be?
Size it from your furniture. Allow about 3 feet of clearance around a dining table and a 3- to 4-foot walking path. As starting points, a bistro set needs about 8 by 8 feet, dining for six to eight about 12 by 14 feet or more, and a lounge area about 12 by 12 feet. A grill zone adds more.
How much slope does a patio need for drainage?
Most designers plan about 1/8 to 1/4 inch of fall per foot, roughly 1 to 2 percent, away from the house. The slab should stay below door thresholds, and water should be directed to lawn, planting beds, or a drain rather than toward the foundation.
What patio finish works best in Seattle's rain?
Textured finishes such as broom and exposed aggregate keep the best grip when wet and handle moss well in shade. Stamped finishes work for dining areas when sealed, and smoother stained or colored finishes are best kept under cover.
Do I need a permit for a backyard concrete patio in Seattle?
SDCI lists patios and concrete slabs on grade among work that usually doesn't need a permit, unless the property is in an environmentally critical area. Size still matters: adding or replacing 750 sq ft or more of paving requires an SDCI grading permit and brings drainage review. Projects still have to meet code and development standards.
Can a patio include built-in steps or seat walls?
Yes, and they are best planned with the patio so forms, footings, and drainage are designed together. Seat walls can double as a grade break on sloped lots. SDCI lists some retaining walls not over 4 feet tall, measured from the bottom of the footing, among work that usually doesn't need a permit.
