I have an old cedar deck, and most of the decking and vertical support posts are rotted out. I'd like to rebuild the deck as-is, just replacing the rotting pieces.
The current design is as follows:
- 2×8 treated ledgers anchored to concrete foundation
- 2×8 treated joists coming off the ledgers
- 2×8 treated rim joists around the edges
- 4×4 cedar posts around the edges (4 foot intervals), sitting on concrete footings
- Posts are notched and are supporting the rim joists, attached with nails
- There are no other supporting posts or beams
- Deck extends about 8 feet out from the house
- Deck is about 4 feet off the ground for one section, and 2 feet off the ground for the other section
- Deck is located in Texas, so snow is not a concern
My concern is that all the information I've found on decks shows people using 6×6 posts as the main supporting structure, with beams on top of those and joists on top of the beams. I only see 4×4 posts used to form the supports for the railings.
I'm hoping to use the current design, and replace all of the posts, decking, and railings. The only significant change I have planned is to attach the posts to the rim joists using carriage bolts instead of nails. Is it reasonable to have 4×4 posts as the primary support, or do I need to consider more significant design changes?
Best Answer
Around here, 4x4s are not uncommon. This table shows that a 4x4 pine post that is 6 ft or shorter can support a load area of up to 10 ft² assuming 50 lbs/ft².
Don't trust me or a random table on the internet; make our own calculations from tables in the building code or other trusted sources and consider having them checked by an engineer.