20x20 Deck Plans
Twenty by twenty, 400 square feet, and the one design here framed with two beams. No prescriptive joist spans twenty feet in a single piece, so rather than an oversized joist this deck gets a second beam on its own posts partway out: the joists span about ten feet twice, lap over the middle beam, and ordinary 2x8s carry the whole thing. It is how a deck this deep is actually built.
It is drawn on a generic lot, so the site plan here does not show a real property. When you run your own address, we pull your parcel, lot shape, and setbacks from public records and redraw the whole set around your actual house.
Deck specifications
| Deck size | 20'-0" x 20'-0" (400 sq ft) |
| Height above grade | 4'-0" |
| Attachment | Ledger to house band joist |
| Joists | 2x8 at 16" on center, two spans, lapped over the interior beam |
| Beams | 3-ply 2x12 outer + 3-ply 2x12 interior, dropped |
| Footings | 16" diameter outer row, 18" diameter interior row, 36" deep (8) |
| Decking | 1x6 composite |
| Guard rail | 36" Fortress rail system |
| Stairs | One straight flight, front edge, 4'-0" wide |
| Design loads | Moderate snow, cold frost zone |
What is in the 7-sheet set
Every sheet carries a title block, and every structural member cites the 2021 IRC section it was sized from. These are not stock previews. They were drawn by the same pipeline that will draw yours.
Using this for a permit
Most building departments want a site plan showing the lot, house, deck, and setbacks, plus a framing plan, elevations, structural details, general notes, and the ledger attachment detail. This set has all of them. Download the sample to see exactly what a reviewer would be looking at, then generate the same set against your own lot.