Civil and site engineering

Grading and Drainage Plan for Your Permit

A grading and drainage plan that moves water away from your building and off your lot the way your county requires.

Stamped by a PE licensed in your state
Drawn to IBC, IRC and local amendments
Plan-check comments answered

Water always finds a path. The plan decides which one.

Poor grading is behind many of the most expensive problems on a property: wet crawlspaces, cracked slabs, eroded slopes and disputes with neighbors over runoff. That is why so many building departments require a grading and drainage plan before they issue a permit for a new home, addition, ADU, garage or manufactured home, and why commercial sites almost always need one.

PE Engineer prepares grading and drainage plans that show existing ground, finished floor elevation, proposed grades, slopes away from the building, swales, area drains, downspout routing and the point where water leaves the site. For small sites we keep the plan simple and readable. For larger sites we add earthwork quantities, drainage calculations and construction details.

Plans are prepared to the grading ordinance and drainage standards of your city or county and sealed by a Professional Engineer licensed in your state. When topographic data is needed, we work from a survey you already have or coordinate with a local licensed surveyor.

What you receive

Existing and proposed contours or spot elevations
Finished floor and pad elevations
Drainage arrows, swales and slope labels
Area drains, downspouts and outfall details
Erosion and sediment control notes
PE stamped grading and drainage plan

What our grading plans address

A good grading plan balances drainage, earthwork, access and the building's foundation in one coordinated drawing.

Positive drainage from the building

Finished grades that slope away from the foundation for the required distance, so roof and surface water never collects against walls, slabs or crawlspace vents.

Finished floor elevation

A floor elevation set high enough above surrounding grade, street gutters and any flood elevation, while keeping driveway slopes and steps practical for daily use.

Swales and area drains

Shallow swales, yard drains and catch basins that collect water from side yards and low spots and carry it to an approved discharge point.

Downspout and roof drain routing

Downspout connections to splash blocks, pop-up emitters, dry wells or storm drain lines, coordinated with the roof plan and any stormwater requirements.

Cut, fill and slopes

Earthwork limits, maximum slope ratios, retaining wall locations and approximate cut and fill quantities so the contractor can price the dirt work accurately.

Neighbor and street protection

Drainage that does not increase or concentrate flow onto adjacent properties, and driveway and curb details that keep water out of the garage and off the street.

When a grading and drainage plan is required

Each jurisdiction sets its own thresholds, but grading and drainage plans are commonly required in these situations:

New homes on vacant lots, almost always, so the county can confirm the house drains properly and does not harm neighbors.
Additions, ADUs and garages that change grades, add significant roof area or sit close to a property line.
Manufactured home installations, where many counties require a plot plan showing pad elevation, drainage and setbacks before the installation permit.
Earthwork above the volume or depth that triggers a grading permit under the local ordinance.
Hillside and sloped lots, where cut and fill slopes, retaining walls and drainage must be engineered.
Commercial pads and parking lots, which nearly always need engineered grading, drainage and stormwater design.

Some departments accept a simple plot plan with spot elevations and drainage arrows for small projects. Others require full contour grading with calculations. If your permit application came back with a request for a grading or drainage plan, send us the comment, and we will prepare exactly what the reviewer is asking for. When the plan also needs to show setbacks and building layout, we coordinate it with our site and plot plans so both sheets agree.

How we design lot grading

The building code sets the starting rules. For residential lots, the IRC requires grades to fall a minimum of 6 inches within the first 10 feet away from the foundation, with alternatives such as swales or drains where lot lines, walls or other obstacles prevent that. Impervious surfaces next to the building, such as patios and walks, must also slope away. The IBC has similar provisions for commercial buildings. Local ordinances add requirements for maximum slopes, setbacks of cut and fill from property lines, and how runoff may leave the site.

Our design process follows a consistent sequence:

Establish existing grades from a survey, county data or field measurements.
Set the finished floor elevation relative to the street, utilities, neighbors and any flood elevation.
Shape the yard so water flows away from the building to swales and drains.
Route collected water to an approved outlet, such as the street, a storm drain, a natural drainage path or an infiltration feature where permitted.
Check slopes for mowing, walking and erosion, and add retaining walls where grades change too quickly.

Where cut and fill slopes are needed, they are typically kept no steeper than 2 horizontal to 1 vertical unless a geotechnical engineer approves steeper slopes. We note compaction requirements for fill under slabs and footings so the grading supports the foundation rather than undermining it.

Drainage problems on existing properties

Not every grading plan is for new construction. Homeowners and property managers contact us when water is already causing damage: a basement that floods in heavy rain, a garage slab that collects water, erosion along a slope, or a neighbor complaint about runoff. Some jurisdictions require a permit and engineered plan for the corrective work, especially when it involves new drain lines discharging to the street or significant regrading.

For existing properties, we review photos, a site sketch and any available survey, identify where water is coming from and where it is trying to go, and design a practical fix. Common solutions include regrading the first few feet around the foundation, adding swales along side yards, connecting downspouts to solid pipe that discharges away from the house, installing area drains at low points, and adding curb cuts or trench drains at driveways.

We aim for the simplest solution that works. A few inches of regrading and a downspout extension often solve problems that a contractor might otherwise address with an expensive interceptor drain. Where the problem involves a failing slope or wall, our retaining wall design service can address the structural side in the same set of plans.

Coordination with stormwater, foundations and surveys

Grading rarely stands alone. When new roofs and pavement add enough impervious area, the local stormwater ordinance may require detention, retention or infiltration, and the grading plan has to direct water to those features. Our stormwater management design is prepared on the same base drawing so the two never conflict.

Grading also affects foundations. A stepped footing, a deeper stem wall or a retaining wall may be needed where the finished grade changes along the building. We coordinate finished grades with the foundation design so footing depths, frost protection and slab elevations line up with the civil plan.

Accurate existing grades are the foundation of the whole design. If you already have a topographic survey, we use it directly. If you do not, we can coordinate with a licensed land surveyor in your area. For some small residential projects, jurisdictions accept plans based on county GIS contours and field measurements, and we will tell you if that is an option for your site.

If plan review issues comments, we respond and revise within the original scope at no extra charge. Most residential grading plans are delivered within a few business days of receiving complete site information.

You likely need this if

The county asked for a grading or drainage plan
You are building a new home or ADU
You are installing a manufactured home
The lot slopes or drains toward the house
A neighbor complained about runoff
You are moving more than a small amount of soil

Talk to an engineer

Have plan-check comments or a tight deadline? Call +1 (424) 428-2898 or send the details and we will reply with a fixed-fee quote.

How it works

From first message to stamped drawings, you deal directly with the engineering team.

Step 1

Send your project

Fill out the quote form with the address, scope and any drawings, photos or plan-check comments you already have. Two minutes is enough.

Step 2

Get a fixed-fee quote

An engineer reviews the scope and replies with a clear fixed price and delivery date for your grading & drainage plans drawings. No hourly surprises.

Step 3

Engineering and drafting

We run the calculations, prepare the drawings to the codes your jurisdiction enforces, and check every sheet before sealing.

Step 4

Stamped set delivered

You receive the sealed PDF set ready to submit. If the plan reviewer has comments, we answer them and revise at no charge within scope.

Codes and standards we design to

Grading and drainage plans follow the codes and local ordinances your jurisdiction has adopted, including:

International Residential Code (IRC) site grading and drainage provisions
International Building Code (IBC) site grading provisions and Appendix J, Grading, where adopted
Local grading ordinances and drainage design manuals
Local stormwater and erosion control ordinances
FEMA and local floodplain requirements where the site is in a flood zone

How licensing works. Engineering drawings must be sealed by a Professional Engineer licensed in the state where your project is located. PE Engineer works with a network of state-licensed PEs, so every set we deliver is reviewed and stamped by an engineer who holds an active license in the state where your project is located. Their name and license number appear on the seal, exactly as your building department requires.

See every state we serve

Related services

Stormwater ManagementDetention, retention and infiltration design, runoff calculations, erosion control plans and SWPPPs prepared to local stormwater ordinances and PE stamped.View service

Site & Plot PlansScaled site and plot plans showing property lines, setbacks, easements, lot coverage, utilities and drainage for residential and commercial permits.View service

Retaining Wall DesignConcrete, masonry, segmental block and timber retaining walls designed for soil pressure, surcharge and drainage, with stamped plans for your permit.View service

Frequently asked questions

What is a grading and drainage plan?

A grading and drainage plan is a drawing that shows the existing and proposed ground elevations on a site, the finished floor elevation of the building, and how surface water will flow away from the building and off the property. It often includes swales, drains, downspout routing, slope labels and erosion control notes.

Do I need a survey for a grading plan?

It depends on the jurisdiction and the site. Many counties require a topographic survey for new homes and sloped lots. For smaller or flat residential projects, some accept engineered plans based on GIS data and field measurements. We will tell you what your jurisdiction typically accepts and coordinate with a surveyor if needed.

How much slope does the ground need away from my house?

For residential construction, the IRC requires the ground to fall at least 6 inches within the first 10 feet from the foundation, with swales or drains allowed where that is not possible. Paved surfaces next to the house must also slope away. Local codes may add stricter rules.

Can you fix an existing drainage problem?

Yes. We review photos, a site sketch and any survey, identify the source and path of the water, and design practical corrections such as regrading, swales, downspout piping, area drains or trench drains. If the work needs a permit, the plan is sealed and ready to submit.

What is the difference between a grading plan and a site plan?

A site plan shows the building location, setbacks, driveways and property lines. A grading plan shows elevations, slopes and drainage. Many permits require both, and on smaller projects they can be combined on one sheet. We prepare them together so the information is consistent.

How long does a grading and drainage plan take?

Most residential grading and drainage plans are delivered within a few business days once we have the site information we need. Larger commercial sites and plans that require stormwater calculations take longer. We provide a fixed-fee quote, usually the same day, and rush service is available.