Greenhouse

Lean-to greenhouse attached to the south side of the house, sitting on the elevated deck. Twin-wall polycarbonate panels throughout on an aluminum frame. Has a linoleum floor with a center drain that pipes through the deck to daylight below.

Status

Active — needs cleanup and repairs before it can be used for growing.

Plans

Four options, each building on the last. Order matters: drain before insulation (drain work would disturb insulation if done after).

Plan A — Drain only

Fix the floor flange so it’s properly secured and sealed to the floor, and confirm the pipe routing is solid end-to-end. The pipe already has a 45° elbow and one pipe clamp on the main beam — the question is whether the floor flange above is actually screwed down, and whether the bottom end properly connects into the gutter rather than just hanging open.

Materials:

Floor drain flange/strainer (if current one is loose or damaged) — ~$15–25
Silicone or plumber’s putty to seal the flange to the floor
2–3 pipe clamps to strap the pipe to joists — ~$5 (do this regardless; takes weight off the floor fixture and the joist hole)
ABS pipe/fittings if the bottom termination needs work — ~$10–20
Total: ~$30–50

Use plastic sheeting to contain water for plants in the meantime — no further work needed for casual winter use.

Plan B — A + Insulation

Stuff rigid foam into the open joist bays from ground level below, then close it in with plywood. Do drain work first — insulation around the drain area would have to be cut and removed otherwise.

Joist bays are ~8” deep, so three layers of 2” XPS gets to R-30 with a couple inches to spare. For the pipe section, cut pieces to fit on either side of the pipe rather than trying to get a single piece around it.

Sandwich: foam friction-fit between joists → support wires to hold it while working → 1/2” pressure treated plywood screwed to joist bottoms to close it all in.

With R-30 floor and heat bleed from the house wall, should be enough to hold 40°F for winter lettuce growing (combined with a grow light for the short PNW days).

Optional extension: smart plug + milk room heater on the existing outlet, automated off a temperature threshold in HA using the Shelly sensor data.

Materials:

XPS rigid foam board, 2” thickness (Owens Corning FOAMULAR or similar) — 3 layers, measure joist bay width before buying — ~$60–80 for enough sheets
Insulation support wires/hangers — one bag — ~$10–15
1/2” pressure treated plywood for underside sheathing — ~$40–50
Screws for plywood — ~$5
Total: ~$115–150 on top of Plan A

Plan C — B + Redo linoleum Roll new linoleum over the existing — no need to pull the old up unless it’s actively lifting or buckled. Sheet goods mean no seams for water to sneak through. Can run it up the base of the walls a bit for a basic cove effect. Tolerates casual watering without the plastic-liner workaround.

Plan D — Full tile upgrade (next year, pending data from first winter) Tile the entire floor over cement board + waterproof membrane, making it a true wet space with slope to drain. Adds thermal mass for better temperature stability overnight. Reuse removed deck boards in other parts of the deck that are end-of-life. Walls sit on 2x2 bases on top of the existing subfloor — tile over rather than demo to avoid disturbing them. Decision point: review Shelly temperature data after first winter to see if the insulation alone is holding 40°F or if tile’s thermal mass is needed.

Issues Observed

Drain disconnected — the floor drain is not properly anchored; the standpipe just passes through the deck and hangs loose below. Needs to be secured and properly routed.
Polycarbonate panels dirty — roof and wall panels have significant algae/mold buildup on the exterior, blocking light.
Ceiling crack at house junction — diagonal crack where the greenhouse roof meets the house fascia; likely where water infiltrates.
Sliding panels misaligned — the large sliding polycarbonate panels on the north wall don’t appear to seat properly in their tracks.
Deck boards weathered — the surrounding deck boards are in rough shape; peeling and gray, though structurally the frame looks solid.
Base gaps — gaps at the bottom of the wall panels where they meet the deck, potential pest entry.