Construction Type Is the Last Decision, Not the First
The rules treat dock type not as a preference but as a conclusion justified by the frontage. A dock cannot be approved unless the applicant demonstrates that
the type of construction proposed is the least intrusive upon the public trust that will ensure safe docking on the frontage.
Safe docking is the requirement; least intrusive is the constraint. The heavier structure is therefore not the safer answer and not the better one — it is the answer you earn by showing nothing lighter works.
Floating Is Not a Third Category
A floating dock is a seasonal dock, not a sibling of crib and pile. Env-Wt 104.14 defines a seasonal dock as one built such that the structure and all associated supports can be completely removed from the water and its bed during the non-boating season — adding that the term “includes but is not limited to pipe docks and floating docks.” Env-Wt 103.09 defines a “float” not as a kind of dock at all, but as a component of a docking structure supported by buoyancy devices.
The market sells three things; the rules recognise two. The axis that matters is not timber versus pipe versus buoyancy:
A permanent dock is one in which the docking structure or its supports, or both, are designed to remain in place throughout the year.
That is where people come unstuck. Leave a float and its anchors in over the winter and you have not kept a floating dock — you have built a permanent one. The question is never what the dock is made of. It is whether the supports come out.
Can Your Water Carry a Permanent Dock at All?
For most New Hampshire frontage it cannot, which settles crib-versus-pile before it is asked. Two conditions must hold, and the second is a measurement, not an argument: the water must be over 1,000 acres, and the site must be exposed to a design fetch of at least 1 mile between compass headings 245 to 340 degrees, or at least 2 miles between headings 341 to 0 or 0 to 244 degrees, measured from true north.
And “design fetch” is itself defined — the average of at least 11 radials evenly distributed across a 30 degree arc. It is an average across an arc, not the longest sightline down the lake, so a narrow channel of open water pointing at your shore is averaged away by the radials either side of it.
Failing that test is not the end of it. A permanent structure may also be approved on documented wave activity — waves of at least a foot, on four separate four-hour occasions between 15 May and 15 October. And one exemption matters here more than any other: a structure on an island accessible only by watercraft need not prove its exposure at all. Island work has its own logistics, but the permitting door is wider, not narrower.
Pile, Unless You Can Prove Otherwise
Here is the part that reverses most people’s assumption. On a site that clears the permanent test, you do not choose between pile and crib. You get pile unless you can demonstrate that pile is impossible.
Env-Wt 513.15(b) makes open pile construction the standard design, with pile bents at least 12 feet apart centre to centre. Anything else is approved only where the applicant shows both that pilings cannot be driven due to site conditions and that the alternative is the least impacting design there. The demonstration is specified, not left to assertion: it must accompany the application and document trial driving by commercial equipment, probings, or experience constructing immediately adjacent docks.
That is a cost line, and the one that surprises owners: ledge is what defeats a driven pile, and proving ledge generally means putting a probe rig on the water before you hold a permit.
Where a crib is allowed, depth sets its size: a maximum of 6 by 6 feet in water up to 6 feet deep, side dimensions increased by not more than a foot for every additional foot of depth beyond 6 feet, and 12 feet of clear spacing between cribs. A crib in 10 feet of water is therefore not the same crib set deeper — it is a 10-foot-square structure. Depth does not raise a crib so much as broaden it, and the footprint on the lakebed grows with it. Which is why the rules ask you to exhaust the pile option first.
The fee schedule points the same way: $600 plus $6 per square foot of permanent dock surface area, or $3 per square foot of seasonal. And on a water of 1,000 acres or more the standard maximum is 6 by 40 seasonal against 6 by 30 permanent — so the heavier dock is also the smaller one, and the dearer application. Build costs sit on top.
Ice Does Not Negotiate
Ice is why the seasonal forms dominate here, and the rules bind the season to it: a seasonal structure on a lake must be installed after ice-out and removed prior to ice-in. NHDES states it plainly: seasonal docks cause fewer lake impacts and do not require aerators against ice damage. A permanent structure spends every winter of its life in the ice — which is why an “ice cluster”, pilings grouped at the lakeward end purely to take ice, is a defined structure in its own right.
And one obligation rarely features in the sales conversation: if a permanent structure is not maintained so as to be usable for its intended purpose, the owner is required to remove it. A crib or pile dock is an asset while maintained and a liability the moment it is not — and that liability runs with the property. Our ice-out record is the other half of the calculation.
Three Feet Decides It
If permanent is closed to you, the choice between pipe, roll-in and float is yours, and one number governs it: a boat slip is a defined volume of water 20 feet by 6 feet by 3 feet deep, measured at the normal high water mark.
How far out you must go to find 3 feet settles the form — a gradual shelf favours a roll-in, a fast drop a float, a firm bottom at moderate depth driven pipe. Which is this page in miniature: read the water first, and the structure follows.
Questions
Is a floating dock seasonal or permanent?
Seasonal. Env-Wt 104.14 defines a seasonal dock as one built so the structure and all associated supports can be completely removed from the water and its bed in the non-boating season, and says the term includes pipe docks and floating docks — a method inside that category, not a third option beside crib and pile.
Can I leave the float in over winter?
Not and still have a seasonal dock. A permanent dock is one whose structure or supports, or both, are designed to remain in place year-round — so a float left in with its anchors is a permanent structure, with the 1,000-acre and exposure tests that follow.
Why can’t I simply ask for a crib?
Because open pile is the published standard design. A crib is approved only where you demonstrate that pilings cannot be driven at your site and that a crib is the least impacting alternative — documented with trial driving, probings, or experience on adjacent docks.
Approval criteria, exemptions, dimensions, pile and crib design and the seasonal obligations per Env-Wt 513.03, 513.04, 513.11, 513.15 and 513.22; definitions per Env-Wt 100; fees per RSA 482-A:3, I(b); boat slip dimensions and the aerator position per the NHDES Docks in Non-Tidal Areas FAQs. Retrieved 2 October 2026. Thresholds in full: our NH dock permits page.
Orientation, not legal advice. Prime wetlands, shoreland conditions, existing structures and local requirements can all change the answer for a particular property. NHDES administers these rules and is the authority.