How can I add joists to a deck that abuts a brick wall?

Question

I have a house that was built in 2006 that has 2x8’s running through the brick out with no header shown. Currently the deck is 24” on center and was contemplating adding another joist in between the joist currently.

My question is this can I use double hangers to create a header in between the joist to then use a hanger to run a joist? Or will this add to much weight to the deck currently. I was thinking of doing this to remove any “bounce” in the deck as well as give a better environment for Trex.

Deck spans 13' from house, 30' long, 24" on center 2x8's.

The other option is going with 2x6 decking and staining. Thoughts, issues, comments? Anything is helpful.

Answer 1

I'd want the simplest, best looking, and least costly solution. Here's my idea.

Sister 2x10 or 2x12 joists to every second or third existing joist. They'll stiffen things substantially, and the decking will spread load from adjacent joists to the new ones. I might skip the outer existing joists to reduce the visual impact of the new ones from outside.

The new joists would not have to be 100% of the existing joist length. They can be fit between the brick and beam and still perform as intended. You could install hangers on the beam, but I don't consider that necessary and it would degrade appearance. Use a robust pattern of corrosion-resistant screws or bolts to bind the members together, with concentrations near the ends.

Use composite decking designed for 24" centers. It can be found in 1½" thickness for this purpose. Cost will be a bit more, but you've saved some by using fewer new joists, hangers, and fasteners.

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Your idea of creating beams between the existing joists has potential, but think for a minute about how many parts and pieces that would take. It's a massive project and would look quite messy from below. Note that you wouldn't need doubled beams for that short span.

Answer 2

13 feet is a long but acceptable span for 2x8s at 24", with the thinner 5/4 deck boards. The (apparent) lack of ledger might be unusual, but if joists are properly spaced and properly supported by the brick wall, that's probably a non-issue.

If you're experiencing bounce, two ways to reinforce are to add blocking between joists midway between the house and the beam, or using 2x deck boards instead of 5/4. Thicker decking has a not-insignificant additional weight, which should still be OK with your 2x8 joists at 24" spacing, but reinforcing the joists as well is probably necessary.

However, it also sounds like you're considering replacing the decking with composite; your 24" joist spacing is likely insufficient for typical composite which requires tighter joist spans usually (mine is at 12", but 16" might be allowable). You'll get more mileage out of composite if you also replace beams and joists, especially if they're in bad condition (the photos aren't great, but it looks like your joists are old). Composite deteriorates very slowly, but wood (cedar, pressure treated) much more quickly so composite deck failures are usually on the wood supports.

If you replace the entire deck, you can have the plan for the new one evaluated for proper joist depth (based on the span given in an edit it likely should be 2x10 not 2x8) and spacing (dictated by the type of decking surface you use) as well as address any concerns you have with the house connection, putting the new one directly on brick like this one or using a proper ledger.