Deck Stair and Guard Deficiencies With a Hot Tub Request
An exterior deck is framed 1.5 m above grade with a 3.6 m wide stair. The stair has 14 risers and a total run of 3.4 m, framed with three 2x10 stringers at 400 mm centres. The stringers are notched 90 mm deep at each tread and bear on a concrete pad at the bottom; there is no intermediate support. The guard posts are fastened to the rim joist with four 1/2-inch lag screws through the siding, and the deck ledger is attached over the exterior siding with lag bolts at 400 mm centres; no flashing was installed above the ledger. The stair handrail is 900 mm above the tread nosing, and the guard infill has openings of 120 mm. The homeowner wants to add a hot tub near the stair opening and asks whether the frame can handle it. The deck is 10 years old and the lag bolts show some rust at the washers.
1. Identify the stair, guard and ledger deficiencies that must be corrected before the deck is used.
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The stair stringers are suspect: 2x10 members spanning 3.4 m with 90 mm notches at every tread have reduced sections and no intermediate support, so their capacity cannot be assumed. The guard posts are fastened through siding to the rim joist with lag screws; that is not a reliable guard load path, because siding is compressible and the connection may not resist a concentrated push. The ledger is bolted over siding without flashing, which invites rot at the rim and ledger, and rusted washers suggest moisture or movement. The 120 mm guard openings exceed the 100 mm sphere limit, so a child could pass through. The handrail height may be within common limits, but it must also be graspable and continuous. These are not cosmetic issues; they affect structural and fall safety.
2. Can the existing deck frame support a hot tub? What would you require before answering?
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The existing frame cannot be approved for a hot tub from the information given. A filled hot tub creates a heavy concentrated load, often several times the design live load of a residential deck, and it may be located near the stair opening where framing is interrupted. Before any answer, a qualified person should evaluate the joist span, beam size, post capacity, footing size and depth, ledger attachment, and connection to the house. The deck is 10 years old and shows rusted hardware, so hidden rot and corrosion must be investigated. A hot tub may require additional beams, posts, footings and framing designed for the load. The homeowner should be told that the deck cannot be used for the hot tub until a design is provided and the repairs are inspected.
3. Outline a repair and verification plan.
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First, shore or limit use of the stair and guard area while it is opened up. Remove the stair and inspect the stringers; replace them with stringers designed for the actual span, notching, and load, or add an intermediate support designed for the stair. Rebuild the guard posts with a positive connection to the deck framing, such as through-bolts or engineered brackets with blocking, not lag screws through siding. Remove the ledger area siding as needed, inspect for rot, install proper flashing, and reconnect the ledger to the house structure per code and manufacturer requirements. Reduce guard infill openings to less than 100 mm and verify handrail height and graspability. Replace corroded fasteners. After repairs, have the framing and guard connections inspected before the hot tub is considered, and verify the final structure under load.