Before starting patio projects: a planning guide

A patio is a drainage project with a decorative surface on top. Almost every failure that shows up in year three, from settling to heaving to a stained foundation wall, was decided during the two days before excavation started. This guide covers those two days.

What to take away

• Establish where water goes before choosing a single paver, tile or slab finish.
• Have utilities located and marked before any digging, every time, on every property.
• Base depth and compaction matter more to longevity than the surface material does.
• Set the finished height at least a few inches below the door threshold and sloped away from the house.

Survey the site before you draw

Start with a hose and a bucket of water on a dry day. Pour water at the proposed high point and watch where it goes. Then check the roofline: downspouts that currently discharge onto lawn will discharge onto your new surface unless you plan otherwise. Note the door threshold height, the finished grade at the foundation, any low corner that stays wet, and the location of the meter, the septic field and the irrigation lines.

Then call for utility locates. This is not optional and it is free in every state. Mark the results on your plan and keep the ticket number. Once the marks are down, the plan can be finalized with confidence about what is under the site rather than optimism about it, which is the same discipline that keeps a patio budget honest.

Water first, everything else second

Run the numbers on runoff before choosing materials. NOAA's education collection on watersheds, flooding and pollution sets out how water moves across land into local waterways, which is a helpful frame for a decision most homeowners treat as cosmetic: every square foot of new hard surface is water that used to soak in and now has to go somewhere specific.

Three workable answers exist. Slope the surface away from the house at a consistent fall and let it discharge onto planting. Use a permeable system with an open-graded base that stores and infiltrates. Or install a collection point piped to daylight or a dry well. Choose one deliberately. The failure mode is choosing none and hoping.

The National Weather Service's advice for before a flood makes the same point in a bigger frame, urging households to know their own flood risk rather than assume it. If your site already ponds after a heavy storm, the patio will not fix it and may make it worse.

Base, edge and height

Element	Rule of thumb	Why it matters
Excavation depth	Surface thickness plus base thickness plus bedding	Too shallow is the most common cause of settling
Base material	Compacted in lifts, not dumped in one layer	Uncompacted base consolidates under use
Edge restraint	Continuous, staked, on all free edges	Without it, pavers migrate outward every season
Finished height	Below the threshold, sloped away from the wall	Prevents water and snowmelt entering the house
Expansion and control joints	Per the material's own instructions	Concrete cracks; joints decide where

Local frost depth changes these numbers, so confirm them with your building department rather than a national video. Sorting maintenance expectations at the same time makes year two much less surprising, which is the subject of the first-year maintenance plan.

Common questions

How thick should the base be? It depends on soil, frost depth and load. Ask the local building department or a soils-aware contractor, and write the answer into the scope.

Do I need a permit for a patio? Often not for an at-grade surface, and often yes for walls, footings, roofs, electrical or anything that changes drainage. Ask before ordering material.

Can I pave over an existing slab? Sometimes, if the slab is sound, drains correctly and the added height still clears the door threshold. Cracked or heaving slabs will telegraph through.

What is the most common planning mistake? Setting the finished height too close to the door. It is expensive to fix and it invites water into the house.