Composite Deck Installation Process: What to Expect From Start to Finish

Most homeowners don’t know what actually happens when a deck gets built. They know there’s a crew, and at the end there’s a deck. What happens in between is a bit of a mystery.

That’s worth clearing up – because understanding the process helps you evaluate contractors, ask the right questions, and know whether the work being done on your property is being done correctly.

This page covers the full composite deck installation process as DDT Deck Builders executes it on every project in Oswego, Aurora, and the surrounding Fox Valley area. For the big-picture overview of our work, visit our composite deck installation page.

Phase 1: Design and Estimation

Everything starts with an in-person visit.

We don’t quote decks remotely based on pictures and rough measurements. We come to your home, walk the yard, assess the site conditions, and have a real conversation about what you want to build.

During this visit we’re evaluating several things that affect the design and the build:

Site conditions: Slope of the yard. Soil type (expansive clay soil common in Kane and Kendall County affects footing depth and diameter). Proximity to the house foundation. Overhead obstructions like utility lines or tree branches.

Existing structure: If we’re attaching to the house, we assess the rim joist condition. Old homes sometimes have rim joists with rot or inadequate flashing from a previous deck – this needs to be addressed before the new deck is attached.

Your goals: How you’ll use the space. Entertaining, relaxing, a place for kids to play, a pool surround. Traffic patterns. Whether you want a dining area versus a lounge area. Views you want to capture or screen.

Code requirements: Setbacks from property lines and the house, height above grade, stair requirements, railing requirements. These vary by municipality and we know the Oswego, Aurora, and surrounding area codes.

From this information, we develop a design – sometimes simple, sometimes with multiple options. We discuss material choices, colors, railing style, and any add-ons like pergolas or lighting.

Then we give you a written estimate. Composite deck cost in Oswego and Aurora is detailed in our cost guide, but the estimate you receive from us is specific to your project – not a per-square-foot average.

Phase 2: Permit Submission and Approval

Once a contract is signed, we prepare permit documents and submit to the municipality.

In Oswego and most surrounding communities, a deck permit application requires:

A site plan showing the deck location relative to property lines, the house, and easements
Structural drawings showing post locations, beam sizes, joist spacing, and railing details
Sometimes: engineering stamped drawings for larger or more complex structures
The permit fee (calculated based on project valuation)

We prepare all of this. You don’t need to do anything except sign documents when required.

Deck permits in Oswego and Kane County are not optional. We won’t start construction without an approved permit. The permit protects you from liability, ensures the work is inspected, and protects your ability to sell the home.

Permit approval timelines vary by municipality. Oswego typically processes permits within 2 to 4 weeks. We don’t start construction until the permit is in hand.

During this waiting period, we finalize material orders. Lead times for composite decking can be a few days to a few weeks depending on the product, the distributor, and the season. We coordinate delivery to align with construction start.

Phase 3: Site Preparation

Before any lumber is cut, the site gets prepped.

Vegetation removal: We clear the area under the deck footprint – grass, plants, roots near the post locations.

Footing layout: Using the approved drawings, we locate post positions precisely. We use batter boards and string lines to establish the deck perimeter and confirm it’s square. Getting this right at the start is critical – errors here compound through every subsequent step.

Footing excavation: We use a power auger to drill footing holes at each post location. In the Oswego area, footings must go a minimum of 42 inches deep to get below the frost line. This is non-negotiable. Shallow footings heave when the ground freezes, which destabilizes the entire structure.

Concrete pour: We pour concrete into the footing holes and set post bases (or embedded posts, depending on the design) at the correct height and alignment. Concrete needs time to cure before we load it with structural weight – typically 24 to 48 hours minimum.

This step is where some contractors cut corners. Shallow footings, undersized concrete, no post bases – these are the failure points that cause decks to shift, lean, or fail structural inspection years later.

Phase 4: Ledger Attachment (for Attached Decks)

If the deck is attached to the house, the ledger board is one of the most critical elements.

The ledger is the horizontal board bolted to the house’s rim joist. It carries the load of the deck’s inner edge. If the ledger isn’t properly attached – or worse, if water gets behind it – the rim joist rots, and you eventually have a serious structural problem.

Proper ledger installation involves:

Removing siding in the attachment area
Installing flashing that directs water away from the house framing
Using the correct lag screws or through-bolts at the proper spacing per the load calculations
Allowing for drainage behind the ledger

This step gets inspected by the building department. An inspector who sees improper ledger flashing will fail the inspection and require a correction. We do it right the first time.

Freestanding decks (not attached to the house) don’t require a ledger, but they require additional posts and beams to carry the load that would otherwise be handled by the ledger.

Phase 5: Beam and Joist Framing

With footings cured and the ledger in place (for attached decks), we build the frame.

Posts: Pressure-treated posts rated for ground contact are set on post bases. Posts are plumbed (verified perfectly vertical) before attachment.

Beams: Built-up or solid beams span between posts. Beam size is determined by the span and the load calculations – this isn’t guesswork.

Rim joists: The outer perimeter of the deck frame.

Joists: Interior framing members that support the decking boards. Joist spacing matters enormously for composite decking. Most composite manufacturers require 12-inch on-center spacing for straight installation and 12-inch on-center for diagonal or picture-frame patterns. Composite deck framing requirements from the decking manufacturer are specifications we follow precisely – violating them can void the product warranty.

Blocking: Solid blocking between joists prevents rotation and provides a solid surface for railing post attachment.

The completed frame is what gets inspected before decking begins. The inspector verifies footing depth (via permit documentation), framing size, joist spacing, ledger attachment, and other structural elements. We pass this inspection, every time.

Phase 6: Composite Deck Board Installation

With an approved framing inspection, boards go down.

Starter strip: Most composite systems use a starter strip at the house end to set the spacing for hidden fasteners.

Hidden fasteners: Quality composite installations use clip-style hidden fasteners that attach to the joist and engage a groove on the edge of the board. This eliminates visible fasteners on the deck surface for a clean, finished look. End joints (where boards end between joists) use face screws that are color-matched to the board.

Spacing: Composite boards need consistent end-to-end and side-to-side spacing to allow for thermal expansion and drainage. The fastener system handles side spacing. End spacing is set manually. In Illinois, where temperatures swing dramatically, this expansion allowance matters.

Cutting: Composite boards require the right blade – typically a fine-tooth carbide blade run at appropriate speed to prevent chipping or melting the cap. End cuts expose the board core and may need to be sealed with end cap material, depending on the manufacturer’s recommendations.

Pattern execution: Diagonal patterns, picture-frame borders, and multi-directional designs require more planning and more waste material. We account for this in the material estimate.

Board selection and layout: We inspect boards before installation, keeping consistent grain direction and avoiding any pieces with manufacturing defects.

Phase 7: Stairs, Railing, and Finishing

Stairs: Stair construction involves stringers (the diagonal structural members), treads (the composite boards you step on), and risers (vertical faces, open or closed). Stair pitch and rise-run ratios are specified by code. Stair nosing composite pieces provide the finished look on tread edges.

Railing posts: Railing posts must be mounted through the decking into the framing below – not just attached to the decking surface. This is a structural requirement. We install blocking at every post location during framing precisely so this can be done correctly.

Railing system assembly: Rail systems (composite top and bottom rails, aluminum or composite balusters, post caps) install on top of the posts. Code specifies maximum baluster spacing (typically 4 inches) and minimum railing height.

Post caps and lighting: Decorative post caps, solar lights, or wired LED lighting get installed as final finishes.

Cleanup: Every project ends with debris removal, concrete cleanup, and site restoration.

Phase 8: Final Inspection and Walkthrough

The building inspector returns for a final inspection. This covers the completed deck – decking, railing height and spacing, stair safety, and overall compliance with the approved drawings.

Once we receive the final inspection approval, we do a walkthrough with you. We point out every element, explain the warranty documentation, cover composite deck maintenance basics, and make sure you’re satisfied before we consider the job done.

Signs of a Quality Installation

When evaluating a completed composite deck – or evaluating a contractor’s past work – look for:

Consistent board spacing, no gaps wider or narrower than others
Clean end cuts with no chipping or rough edges
Railing posts that are solid with no movement
Properly aligned stair stringers with consistent rise and run
Permit card or documentation showing passed inspections
Flashing visible at the ledger-to-house junction

How DDT’s Process Differs

We follow The DDT Standard on every project. That means every step – design, permit, site prep, framing, inspection, decking, railing, final inspection, walkthrough – happens in the right order, with the right materials, done correctly the first time.

We don’t skip inspections. We don’t use shortcuts on footings. We don’t attach railing posts to decking only. These aren’t optional extras. They’re how decks are supposed to be built.

How long the full process takes varies by project size and permit timeline – that’s covered in detail on our timeline page.

Want to see the process in person? Call DDT Deck Builders at 630-200-3945 to schedule a free estimate.

Frequently Asked Questions

Do I need to be home during construction?

Not continuously. We ask that someone is available on day one for site orientation and at the end for the walkthrough. Otherwise, we work independently and communicate daily with project updates.

What happens if it rains during construction?

Light rain on composite framing is fine. We avoid pouring concrete in heavy rain. If weather is severe enough to affect quality or safety, we pause and reschedule. This is part of the process – it’s not something that delays a project significantly in most cases.

Can I change the design after construction starts?

Minor changes are sometimes possible. Significant design changes after framing begins may require a permit revision and additional cost. Get a free estimate and finalize the design before we start.