Flood mitigation · Portsmouth, NH
Flood mitigation in Portsmouth, NH
Elevation, flood resistant foundations and pile support for Portsmouth homes exposed to coastal flooding, tidal creeks and rising groundwater.
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Portsmouth flooding
Two kinds of water to plan for.
Portsmouth faces flooding from above and below. Storm surge and high tides push in from the Piscataqua and the tidal creeks, while groundwater in low parts of the old city rises with the tide and comes up through basements.
The city has mapped historic buildings exposed at a 13.5 foot coastal flood elevation and has studied groundwater flooding in historic Portsmouth. For homeowners, the question is how to protect a particular house.
Our answer depends on the house: lifting it above the flood level, rebuilding the foundation to handle water, adding flood vents, or a combination.
Flood snapshot
Sources
Storm surge, tides and rising groundwater
Waters
Piscataqua River, Sagamore Creek, Berrys Brook
Main fix
Raising the home above the Base Flood Elevation
Other options
Flood vents, piles, foundation waterproofing
Funding
Increased Cost of Compliance coverage may apply
Our approach
Protect the house, respect the history.
Many Portsmouth homes at risk are also historic. We plan flood work so the house is protected without losing what makes it worth protecting, and we coordinate with city review where it applies.
✓ FEMA flood zone and elevation checked for your lot
✓ Lifting, new foundation and site work by one crew
✓ City permits and historic review planned in
Options
Flood options for Portsmouth homes.
Most projects use one or more of these.
Elevate
Raise the house
Lifting above the Base Flood Elevation is the strongest protection from storm surge and tidal flooding.
Foundation
Flood resistant foundations
Walls with flood vents or pile foundations let water pass instead of pushing against the house.
Groundwater
Deal with water from below
Drainage and foundation repairs help homes where groundwater rises with the tide.
FAQ
Flood mitigation in Portsmouth: questions
Why does my Portsmouth basement flood when it is not raining?
In low parts of the city, groundwater can rise with the tide and come up through older foundations. It is a different problem from storm flooding and needs a different fix.
What is the Base Flood Elevation?
It is the height floodwater is expected to reach in a major flood, as shown on the FEMA flood map. Raising a home above it is the standard target for flood protection.
Does FEMA help pay to elevate a home?
It can. Homes with an active National Flood Insurance Program policy that are substantially damaged may qualify for up to $30,000 in Increased Cost of Compliance coverage. Hazard Mitigation Grant Program funds may also be available after federal disasters.
Can a historic home be raised?
Often, yes. We assess the framing first and coordinate with any city review the project needs.
More in Portsmouth
Related work in Portsmouth.
Flood projects usually include these services.
01
House lifting in Portsmouth
Raising the home to its new height.
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02
Foundation repair in Portsmouth
Foundations built to handle water.
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03
Excavation in Portsmouth
Drainage and grading around the house.
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04
Structural repair in Portsmouth
Framing repairs found during the work.
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05
All services in Portsmouth
Back to our Portsmouth page.
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06
Flood mitigation in NH
Our flood mitigation work across New Hampshire.
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Let's talk
Worried about flooding in Portsmouth?
Tell us where the house is and what you have seen. We will check the flood map and lay out your options.
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