Cedar vs Composite vs PVC Decking in Illinois: How Each One Fails
What this comes down to
- Composite decking is not rot proof. Its wood content can still feed decay fungi once moisture cracks the plastic.
- The Forest Products Laboratory ranks cedar heartwood as resistant to decay. That suits above ground use but is not immunity.
- Cedar's resistance can drop in warm, humid climates. The frame under it still needs pressure treated lumber.
- PVC boards contain no wood, yet they still expand, gap at the ends and get hot in the sun.
- Blocked airflow under a PVC deck raises heat build and gapping. The maker calls for open air beneath the boards.
- The code asks plastic composite boards to carry an ASTM D7032 label with allowable load and span.
Cedar, composite and PVC answer one question. How does a deck board survive rain, sun and freezing winters? None of them is maintenance free. They also fail in three different ways, and the difference matters when choosing.
This guide compares what each board is made of and how each one lets go. It draws on federal wood research and a board maker's installation rules. It ends with what no comparison can settle for a particular yard.
Which decking is best in Illinois: cedar, composite or PVC?
None wins on every count. PVC has no wood to rot. Composite keeps some wood inside its plastic. Cedar is natural wood rated resistant rather than immune. The right pick depends on shade, budget and how much upkeep the owner will accept.
Illinois puts every board through humid summers and freezing winters. Moisture is the common stress, and each material handles it differently. The cost side of the choice is in the guide to composite deck cost.
Is cedar decking resistant to rot?
Yes, for above ground use, but it is not immune. The U.S. Forest Service's Forest Products Laboratory ranks the cedars in the resistant class. Western redcedar is included. Its wood handbook decay chapter puts Douglas-fir a step lower.
The Laboratory says resistant heartwood generally gives satisfactory service above ground. A deck board is above ground. The same table warns that resistance may be less in warm, humid climates. It may also be less where wood touches the soil.
Lumber is the catch. The handbook notes that some species are sold mostly as second growth. Those boards carry a high share of sapwood, so heartwood lumber is scarce. Ask which part of the tree a cedar board came from.
Can composite decking rot?
The plastic cannot, but the wood inside it can. Many composite boards blend wood particles with plastic. The Forest Products Laboratory's wood plastic composite research sums up about 20 years of testing. The tests covered fungi and moisture.
Its finding is specific. After an initial period outdoors, moisture swells the wood particles. Microcracks then open in the plastic around them. Those cracks give decay fungi access to the wood component.
Capped boards add a plastic shell to slow this down. A capped board is only as sealed as its shell, and every cut end is a place where the shell stops. Ask how the maker wants cut ends handled.
Does PVC decking get hot, expand or fade?
It does all three to some degree. PVC boards have no wood, so they cannot rot, but they are still plastic in the sun. TimberTech's PVC decking installation guide says all decking gets hot in the sun.
The guide says its PVC boards run cooler than many boards in similar colors. It adds that darker colors feel hotter. It also expects some gapping at board ends and butt joints.
Blocked airflow makes it worse. The guide says obstructed airflow raises heat build. That increases expansion, contraction and gapping. It asks for at least 1.5 inches of clearance in those spots and suggests shorter boards.
Color changes too. The guide says colors may shift as the boards weather. It suggests moving furniture, planters and rugs for even weathering. It warns that rubber or vinyl mats can discolor the boards.
Do the three boards need the same frame?
Yes. Composite and PVC change the surface, not the joists, beams or posts. The frame under every one of these boards is pressure treated lumber. It still gets wet through the gaps. A rotted frame needs repair before any new board goes on.
The code treats the boards differently. The 2018 residential code deck chapter accepts treated or durable lumber. The lumber must be grade No. 2 or better. Plastic composite boards must carry an ASTM D7032 label with allowable load and span.
Composite boards containing wood must also be decay resistant under that standard. They need a flame spread index of 200 or less, and they go in under the maker's instructions. Towns adopt their own editions, as the Illinois deck building code guide explains.
Which board suits sun, shade and stairs?
Sun, shade and airflow decide more than brand names. A low deck with blocked airflow is where the PVC maker's own cautions bite hardest. A deck in full sun runs hot in any material, and darker boards run hotter.
Shade brings the other risk. The Laboratory's decay chapter says fungi need mild temperatures, moisture and air. A shaded, damp deck supplies all three. That matters most for cedar and for composite, which both contain wood.
Anything at ground level is the hardest case. The Laboratory says resistant heartwood suits above ground use. Ground contact calls for the very resistant class. Treated lumber is the usual answer for stair framing at grade.
How do cedar, composite and PVC compare?
Each board has its own weak point, and the weak point decides the care it needs. The table sets them side by side. It also lists what to confirm before ordering, since two boards in one category can differ.
| Board | Made of | How it lets go | What to confirm |
|---|---|---|---|
| Cedar | Natural wood, heartwood rated resistant | Decay where it stays damp or touches soil | Heartwood or sapwood, and the grade |
| Composite | Wood particles in a plastic matrix | Microcracks let fungi reach the wood | Capped or uncapped, and the ASTM D7032 label |
| PVC | Plastic only, no wood | Heat, expansion, gapping and color shift | The maker's gap and airflow clearance rules |
| Frame under all three | Pressure treated lumber | Rot at joist tops, ledger and posts | Condition before new boards go on |
What does a decking swap cost?
The work is priced separately from the boards. The starting prices below cover the labor and the frame. The boards are priced at quote from the brand and profile chosen. Replacement costs overall are in the guide to deck replacement costs.
| The work | Starting price | Wider market | What moves it |
|---|---|---|---|
| Deck board replacement over a sound frame | From $10 per sq ft | $12 to $25 per sq ft | Board type and access |
| Typical 200 sq ft re-deck | From $1,995 | $2,400 to $5,000 | Board brand and frame condition |
| Joist repair or sistering | From $125 per joist | $150 to $350 each | Joist count and span |
| New pressure treated deck | From $24 per sq ft | $26 to $50 per sq ft | Size, height and footings |
| Typical 12 by 16 deck (192 sq ft) | From $4,495 | $4,700 to $9,300 | Footings and railing |
| Minimum service call | $99 minimum | $120 to $200 typical | Time on site |
What cannot be determined before the old boards come up?
How long a particular board will last. No source gives a service life for a deck in a given yard, and warranties differ by brand. The Forest Products Laboratory's grouping ranks decay resistance and does not promise years.
How the frame is holding up. Boards hide the joist tops, the ledger and the posts. A frame with rot needs repair before new boards go on, whichever type is chosen. The fall deck maintenance guide covers what to check.
Decking material questions
Is cedar or composite better for a deck?
Neither wins outright. Cedar is natural wood that the Forest Products Laboratory rates resistant to decay above ground. Composite blends wood and plastic and can let fungi in through microcracks. Both contain wood, so moisture matters for each. The frame under either board is the same treated lumber.
Can composite decking rot?
The plastic cannot rot, but the wood particles inside many boards can. The Forest Products Laboratory found a pattern after an initial period outdoors. Moisture swells the wood and opens microcracks in the plastic. Those cracks give decay fungi access to the wood component of the board.
Does PVC decking get hot in the sun?
Yes, to a degree. TimberTech says its PVC boards run cooler than many boards in similar colors. All decking still gets hot in the sun, and darker colors feel hotter. Blocked airflow under the deck raises heat build and gapping. The maker asks for open air beneath.
How does Perfect Work help choose between cedar, composite and PVC decking?
Perfect Work Remodeling & Repairs starts with the frame, not the boards. Joist tops, the ledger and the posts are checked first. It then looks at sun, shade and airflow under the deck. It prices the board type that fits, with the maker's gap and clearance rules written into the quote.
What does a decking estimate from Perfect Work cover?
A decking estimate from Perfect Work Remodeling & Repairs names the board brand and profile. It also lists any frame repairs found, the fasteners and the starting price for the work. Board replacement over a sound frame starts at $10 per square foot. The brand is settled before the quote, not after.
Does the code allow composite decking in Illinois?
Yes, when it meets the code. The 2018 International Residential Code requires composite boards to carry an ASTM D7032 label. The label states allowable load and span. They must also be installed under the maker's instructions. A town may adopt its own edition and amendments, so confirm locally before ordering boards.
Pick the board after the frame
A decking choice comes down to moisture, heat and upkeep. Cedar and composite both contain wood, PVC does not, and all three sit on the same treated frame. The frame is the part that has to be sound first.
A visit from Perfect Work Remodeling & Repairs starts with the frame under the old boards. Joist tops, the ledger and the posts are checked before a board type is priced. Board replacement is part of its deck services.
Call Perfect Work at 630-297-7888 · Book a deck check