The outlet by our back door came with the house, and with it the flat plastic cover you see on half the exterior walls in America: two spring-loaded flaps, one over each receptacle, closing under their own weight. For three winters a cord ran out from under the lower flap to a string of lights over the patio, which meant that flap spent three winters propped open at an angle, resting on the cord the way a shoe wedges a door. It looked fine to me. When a GFCI started tripping on windy afternoons and an electrician finally pulled the cover off, there was a shallow ring of rust-colored water standing in the bottom of the box and green crust on the receptacle screws. The flap had done exactly what it was built to do. What it was built to do never included a cord.
Two covers that look related and are not
The flat flap cover is weatherproof when it is closed, and only then. Lift a flap, put a plug behind it, and the seal is gone for as long as that plug stays there — which, for most of us, is the whole season. The other kind is a hood: a deep clamshell or bubble that stands off the wall far enough to swallow the plug and part of the cord, with a gasketed knockout at the bottom for the cord to leave through, so the lid still closes on a live connection. In the trade it is an outlet box hood or an in-use cover. Homeowners call it the bubble, which makes it sound like an upgrade for fussy people rather than a specific answer to a specific hazard.
The hazard is water reaching the back of the plug and the face of the receptacle at the same time, where it can bridge the blades to each other or to the box. A closed flap stops that. A propped-open flap collects it, because the flap resting on a cord makes a small sloped roof pointing straight into the opening.
Damp and wet are code words, not weather words
The National Electrical Code splits outdoor spots into damp locations and wet locations, and for receptacles that split decides which cover is legal. In a damp location — a covered porch or a roofed patio that stays out of driving rain — a cover that is weatherproof when the plug is removed is acceptable. In a wet location, which is anything exposed to weather, hit by sprinklers, or washed down, the enclosure has to be weatherproof whether or not an attachment plug is inserted. That single phrase in 406.9(B)(1) is the entire argument, and it rules out the flat flap anywhere a cord lives outside in the rain. Our lights-over-the-patio outlet faced open lawn, which made the judgment call an easy one after the fact. The damp-versus-wet distinction has its own quirks, and the usual homeowner error is assuming a roof overhead settles it. Wind does not read floor plans.
Extra-duty is a listing, not a marketing word
If the weatherproofing in a wet location is provided by an outlet box hood, the Code requires that hood to be listed and identified as extra-duty. The phrase entered the NEC in 2011 for buildings other than one- and two-family dwellings, and the 2014 edition dropped that distinction, so it reached houses too. It exists because the thin hoods of the era kept failing in service — cracked lids, snapped hinges, covers that had been hit once by a wheelbarrow and never sealed again. Extra-duty hoods are evaluated against tougher requirements in ANSI/UL 514D, the standard covering cover plates for flush-mounted wiring devices, and the identification is molded into the cover where an inspector can read it. Products that provide weatherproof protection some other way, without a hood, do not carry that marking and do not need it.
The test at the store is short, then: buying a bubble for an outlet that gets rained on, turn it over and look for the words. A hood with nothing stamped on it is a hood somebody decided was good enough.
The hood keeps weather out; the GFCI deals with what gets in anyway
No cover is a substitute for ground-fault protection, and outdoors the Code has required both for a long time. Receptacles outdoors at a dwelling need GFCI protection, and a one- or two-family house is supposed to have at least one receptacle readily accessible from grade at the front and at the back, mounted no more than six and a half feet above grade. Those two rules are why a house built in the last few decades has a GFCI somewhere near each exterior door, even if the reset button now lives on a breaker in the panel instead of on the outlet face.
The part worth internalizing is what a weather-linked trip means. A GFCI that trips during rain and holds when things dry out is not a defective device being temperamental. It is a working device reporting that current is finding a path it should not have, almost always through moisture, and the honest reading is that water is getting somewhere it does not belong. Resetting it on autopilot every wet week is how a small seal problem turns into the rusted box we found.
What the cord is allowed to do on the way out
A hood only works if the cord leaves through the opening designed for it, at the bottom, with the lid closed around it. Cords that force the lid open or get pinched in the seam undo the arrangement, and a cord thick enough to hold the gasket apart wants a bigger hood rather than more optimism. Outside, use cords marked for outdoor use; the ESFI checklist on safe outdoor use of electricity, published with the Consumer Product Safety Commission, is blunt about that and about storing outdoor products indoors when the season ends. Indoor cords have thinner jackets and connectors that were never molded to keep water out.
Then there is the question the cord itself raises. A cord is temporary equipment, and its ratings assume temporary use. If something outside has been fed by the same cord through two summers — a shed, a pond pump, a set of lights that never comes down — the real answer is a circuit, not a better bubble.
One slow pass around the house, once a season
- Find every exterior receptacle, including the ones behind shrubs, under decks, on posts in the yard, and in the garage wall that faces out.
- Check what is covering each one, and whether anything is plugged in underneath a flap that cannot close.
- On any outlet that gets rained on, look for the extra-duty identification molded into the hood.
- Read the receptacle face for WR, and note the ones that have no marking at all.
- Press the test and reset buttons on outdoor GFCIs, and find out which breaker or which indoor outlet protects the ones with no buttons.
- Open and close each lid. Hinges go brittle in sunlight, and a lid that will not stay shut has stopped being a cover.
- Look for the quiet tells: cracked plastic, a hardened gasket, rust weeping from a box, insects nesting inside a hood.
- Note anything that trips only in bad weather, with the date. Two entries in one season is a pattern worth handing to an electrician.
What we changed, and what it cost
Ours ended as a new weather-resistant GFCI receptacle, a metal extra-duty hood deep enough for the plug we actually use, and a gasket behind the plate — call it an hour of labor and less than the cost of the light string it protects. The patio lights now run from a cord that leaves through the bottom of a closed lid, and the box behind them is dry. What stays with me is that nothing about the old setup looked wrong from six feet away, which is the trouble with outdoor wiring: weather tests it daily and a person inspects it about once a decade.