Foundation installation in Portsmouth NH - a base planned to keep water out
Building new or adding on and unsure what goes underneath? We help you choose the foundation, then pour it with the water plan settled first.
- Fully licensed and insured.
- Free estimates at your property.
- We respond within 1 business day.
What does a new foundation in Portsmouth involve?
The short answer: Foundation installation in Portsmouth, NH means pouring the concrete base your house sits on, either a slab or basement walls, and then coating those walls so the space inside is protected from water.
Most people call us once a house or addition is on paper and the lot is ready, and they want to know what goes underneath and what it'll cost. The price mostly moves with the size of the footprint, a slab versus full basement walls, how much digging and grading the lot needs, and how much water protection goes on the walls. The schedule turns on the city's review of your plans and on the season, since cold weather changes when we can pour. If you're building on a slab, our slab foundation building page covers that job, and either way I'll put your own figure in a written estimate after I see the site.
What on your lot tells you how the foundation should go?
Water that sits after rain
Puddles that hang around for a day, or a low corner that stays soft, tell us water will push against the new walls. If that only comes out after backfill, fixing it means digging the walls back out.
A yard that slopes away
A lot that drops off toward the back often suits a walkout basement, with a door on the low side. Finding that out after the plans are drawn can mean redrawing them and waiting on another review.
An old foundation next door
An addition has to meet the house you already have, so I want to see the old foundation and how water moves around it first. A new wall poured without that check can send water straight toward the old basement.
How our foundation installation works
I start every foundation job by asking how you plan to use the space below, because a finished basement, storage or a crawl space each change what the walls and floor need. Then we lay out the house, dig down to firm ground and check the subgrade, the soil everything sits on, so nothing settles with loose fill. We form and pour the walls with rebar, steel bars set in the concrete that hold it together if it tries to crack apart, and let the concrete cure, the wait while it hardens and gains strength, before anything pushes on it. Before the backfill goes in, I go over the water protection on the walls with you, because once the dirt is back against them it's hard to change. If a budget gets tight, that coating and the drainage at the base of the walls are the last place I'd cut, since nobody sees them on move-in day and they decide whether the space below stays dry.
Every foundation wall sits on concrete footings, so we form and pour those first, and if a porch or small addition only needs footings we do that work on its own. When the building is commercial or multi-unit, the same site often needs concrete parking lot building once the walls are up, and planning the grading for both at once keeps water running away from the building.
Full basement walls
This suits you if you want storage or living space below the house, and on a sloped lot it can open into a walkout. It's the most digging and the most wall to protect from water, so that's where we spend the most time planning.
Slab foundation
This suits a house or addition with no basement, on a lot that's fairly level. There's less digging and less wall, and the work goes into a well-packed base so the slab stays flat.
What happens after you call us about a new foundation?
Here's how a foundation job goes with us, from the first call to the cleanup, and where the city's review fits in between so you can plan the rest of your build around it.
- Step 01
Call or send us a message
Call (603) 956-1034, use the form or email estimates@portsmouthconcreteworks.com, and we'll get back to you to set up a visit. Send your address and any site plan or sketch you already have.
- Step 02
I walk the site with you
I come out myself, walk the lot, and ask how you'll use the space below and where water goes when it rains. Then you get a written estimate for the foundation we talked through, so you know the cost before anything is booked.
- Step 03
Sort out permits and dates
Once you're ready, we work through the city's permit questions and pick a pour date with the season in mind. If your lot is in the Historic District, new construction and additions also need a separate Historic District Commission application, which the city says adds at least a month to review.
- Step 04
Dig, pour, protect and backfill
Our crew preps the base, pours and finishes the footings and walls, and puts the water protection on before the dirt goes back. We clean up the site when we leave, so it's ready for the framer.
What a Portsmouth lot means for foundation installation
Building permits here come from the Portsmouth Inspection Office, which issues them for new construction and general renovation. Its list names structural changes and repairs, not foundation work by itself, so I ask the office what your job needs before we set a pour date, and we help pull together the sketches or drawings they want. Lots in the city's Floodplain District, which covers FEMA flood hazard areas and the city's own extended flood hazard areas, follow extra zoning rules, and if yours is one of them we plan around that review from the start.
In some of the older neighborhoods near the water, groundwater pushed up by rising seas has flooded the basements of historic buildings at the year's highest tides, so on low lots I ask about high water early. We see the same coastal ground on jobs in Rye and Kittery, and on both sides of the Piscataqua River we plan the water side before the walls go in.
Get a written estimate for your new foundation
We respond within 1 business day to set up a visit, and I come out to walk the site myself. The estimate is free and written, and there's no pressure to book.
Why Portsmouth homeowners call Portsmouth Concrete Works
I write your estimate myself
I come out to look at the job and write the estimate myself, and our own crew does the work with me on site for the pours. You talk to the same person from the first walk-through to the pour.
In business since 2017
I started this business in 2017 after years on other crews learning flatwork and foundations, and I first poured concrete patching barn floors on our family farm. That's why the awkward jobs, like sloped yards and tight side lots, are the ones we're known for.
Fully licensed and insured crew
We're fully licensed and insured. That matters on a job with an open hole beside your house and a concrete truck in the driveway.
Site plans drawn with setbacks
Most Portsmouth permit applications need a site plan showing every structure and its setback, the distance from the lot lines, so I note those when I walk your lot. That way the layout we price already has what the city asks to see.
On a foundation, the water side matters most, because it's buried for good once the backfill goes in. Request an estimate or call (603) 956-1034 and tell me what you're building.
Foundation questions from Portsmouth homeowners
Do I need engineered plans for a foundation permit in Portsmouth?
Usually not, because most home projects in Portsmouth don't need stamped structural plans, and the city's code official decides under state law when engineered plans are needed. When the work involves structural parts, the permit drawings show the framing, on either sketches or engineered plans.
What foundation is best for a slab home on a gently sloped lot?
A frost-protected shallow foundation is usually the one to look at first, because insulation warms the soil around the house so the foundation can sit shallower. The builder's guide for this type says it suits slab homes on lots with moderate to low slopes best, where one concrete pour can mean fewer inspections and faster building. It also works for walkout basements, insulated on the downhill side, and for remodels, since it disturbs less of the site.
What is the best way to keep water out of a new basement?
Waterproofing that stretches usually beats standard dampproofing, which is an asphalt coating that generally can't stretch when the wall moves or cracks. The stretchy kind protects the space inside longer and under more water pressure, so ask which one a bid includes, especially on a low or wet lot.
Why add radon protection while the foundation is being built?
Because a radon-resistant system costs a builder much less to put in during construction than fixing a radon problem found later. In a new home it needs no special skills or materials, and it includes features like a layer of clean, coarse gravel under the slab, with methods that vary by foundation type. Ask for it in the foundation plan from the start.
How much does a new foundation cost in Portsmouth, NH?
The cost comes down to the foundation's size, its type and what your lot asks of it, so I give you a written figure after I walk the site. Full basement walls cost more than a slab because there's more digging, forming and concrete, and stretchy waterproofing usually costs more up front than basic dampproofing. A sloped or tight lot, extra drainage, or planning around flood or historic review can add to it too.
How do I check if my Portsmouth lot is in a flood zone?
Start with the city's MapGeo map for a first check, then confirm on FEMA's Map Service Center, which is the official flood source. If your lot is in the Floodplain District, get the rules themselves from the city's floodplain regulations before design starts, and we'll plan the foundation around them.
Related concrete work for a new build
Concrete footings
Porches, decks and small additions often need only footings, the wide pads of concrete under posts and walls that carry the weight down into firm ground.
Concrete parking lot building
A new commercial or multi-unit building usually needs parking beside it, and a concrete lot holds up to plows and daily traffic for years.
Plan your foundation before the design is final
Call (603) 956-1034 while the house is still on paper, since that's when changing the foundation type or the water plan costs the least.