Under the houses in Mystic Island

Mystic Island sits in Little Egg Harbor Township — a large lagoon community in Little Egg Harbor Township.

Housing stock. Predominantly single-storey homes built on filled ground, a significant share never elevated.

Ground and water. One of the most tidally exposed neighbourhoods on the mainland, with canals running back from Great Bay.

Mystic Island is one of the most tidally exposed neighbourhoods on the whole mainland. The community is a dense grid of canals cut back from Great Bay, and the buildable land is fill. That combination means the water table under these homes is effectively an extension of the bay: it rises on the tide, and during a coastal event surge reaches deep into the grid rather than stopping at a waterfront row. A crawl space or slab-edge here contends with salt-influenced groundwater, and the enclosed space beneath the many un-elevated homes floods on events that would leave an inland house dry. Moving water can also wash sand out from under slabs and footings, so settlement that appears after a storm is common here and can surface years later.

Working here. Narrow lots on a grid of canals. Access is almost always from the street, and neighbouring houses sit close.

Around Mystic Island. The work comes from the grid of numbered canals off Radio Road; the streets running back from Great Bay Boulevard; the sections nearest the open water of Great Bay versus the interior canals; the Twin Lakes edge of the community.

On cost here. Access is the recurring cost driver: lots are narrow, houses sit close together, and there is rarely room to bring equipment down the side, so almost everything stages from the street. Where a home has never been elevated, work below the floor also has to be planned around flood-zone rules, which affects scope more than any single line item.

Mystic Island's canal grid means a home three streets back from the bay can be as tidally influenced as one on the open water, which surprises owners who assumed distance from the bay meant a drier crawl space.

The high share of homes never elevated after Sandy means their crawl spaces and slab edges sit closest to the tidal water table, so encapsulation, drainage and settlement work come up here more than almost anywhere else we cover.

Before work starts in Mystic Island

A permit for this address is issued by the Little Egg Harbor Township Building Department — Administrative Justice Complex, 665 Radio Road — 609-296-7241, Monday to Friday 8:30am to 4:30pm.

Little Egg Harbor asks for more survey work than its neighbours, and it has done since 7 November 2016: new construction, additions and substantial improvements in a flood hazard area need two foundation location surveys prepared by a New Jersey professional land surveyor, showing every building corner and the elevation of the top of the foundation, with the documentation in hand before vertical construction goes any further. The township's permit desk also handles bulkhead applications, house-raising and elevation of existing buildings from the same counter as ordinary construction permits, which tells you what kind of work it sees most.

In a mapped flood zone the size of the job decides which rulebook applies to it. If the cost of the work reaches 50% of the structure's pre-improvement value, it counts as a substantial improvement, and the whole building — not just the part being worked on — has to be brought into compliance with current flood standards. That can mean elevating a house that has sat where it is for sixty years. Phasing work to stay under the threshold is legitimate; discovering the threshold after the contract is signed is not a good afternoon. 44 CFR 59.1; local flood damage prevention ordinances

This does not mean every house has to come up. An existing home is not required to be elevated because the standard changed. What triggers compliance is the work itself — a substantial improvement, or substantial damage — not the age of the house or the zone it sits in. A crawl space encapsulation or a crack repair on its own does not put a homeowner anywhere near that line.

Nobody should take a flood zone designation off a web page, including this one. The authoritative map is FEMA's Map Service Center, which gives the zone and base flood elevation for a specific address rather than a street or a neighbourhood — and the difference between one side of a street and the other is real down here. The faster route is often the municipality itself: towns keep the elevation certificates submitted for construction on file and will release one on request, and that certificate tells you where a particular house actually sits relative to base flood elevation, which is the number that decides what any foundation work has to comply with.

We do not publish a permit fee for Little Egg Harbor Township until we have read it off the municipality's own schedule, so call the office for the current number rather than working from a figure found elsewhere.