Slab foundation building in Alexandria VA - a solid base planned before the pour
Building a home or addition on a slab? We sort out the soil, gravel and plastic first, then pour the foundation.
Get your slab foundation planned right
Call (571) 760-4255 or send the form early, because the paperwork and soil questions usually set the pour date before the concrete does.
What goes into a slab foundation for a new home or addition?
Slab foundation building in Alexandria means pouring a concrete slab over a layer of gravel topped with heavy plastic sheeting, so the slab itself serves as the foundation for a new home or an addition.
Most people calling about a slab are building a new house or adding onto one, and they want to know what it'll cost and when the framers can start. The price moves with the size of the slab, how much digging and packing the ground needs, how much steel goes in and what a soil report calls for, if there is one. The schedule usually turns on the soil report and the paperwork more than on the pour itself, and once we know which office covers your address, we take care of the permit work for our part of the job. Your estimate spells out what's included, such as removal and haul-away, so you can compare it fairly with other bids.
Why Alexandria homeowners call J&K Alexandria Concrete Company for slab foundations
I write the estimate myself
I come out to look at the job and write the estimate, and our own crew does the forming, pouring and finishing. The person asking the questions up front answers for the work.
Your address, the right office
An Alexandria mailing address isn't always inside city limits, and your tax records show which office covers you. We sort that out and handle the permit work for our part of the job.
Built by someone who framed houses
I framed houses for years before I switched to concrete, so I know what the walls need from the slab under them. We've run this business since 2017. We're licensed and fully insured.
On a slab, the part that matters most is the part you won't see again: the soil, the gravel and the plastic under it. Tell us about your project and I'll come take a look.
How we build a slab foundation
If there's a soil report, I read it first, because it tells us what the ground can carry and it shapes the slab before anyone digs. Our crew digs out to the subgrade, the soil the slab rests on, and packs it firm instead of raking it level, since loose dirt keeps settling after the pour. Then comes a gravel layer with heavy plastic sheeting over it, which you and I plan together ahead of time, and the plastic also keeps wet concrete from clogging the gravel. We set the forms and the rebar, steel bars that hold the slab together if it tries to crack, check where the water will run, and pour early in the day so midday heat doesn't leave a weak, dusty top. After that the slab needs time to cure, the slow hardening that gives concrete its strength, before anything heavy goes on it.
A slab is often one piece of a bigger job. When the design calls for a basement or crawl space instead, that's our foundation installation work, and if you're putting up a small commercial or rental building, we can handle concrete parking lot building too, so the lot and the building pad get planned together.
Slab for a new home
This suits owners building a house from the ground up. We plan the slab around the soil report and the house plans, so the layout, the openings for pipes and the steel are settled before the pour.
Slab for an addition
This suits a room or wing added onto your house. The new slab has to meet the existing foundation at the right height, so we check what's there before we set the forms.
Is your lot ready for a slab foundation?
Water pooling on the lot
Puddles that sit for days where the house will go usually mean the ground drains poorly. Pouring over that without a plan invites settling and a damp floor later.
Soft or spongy ground
Ground that gives underfoot, or a lot that was filled at some point, usually needs more digging and packing. Finding that before the forms go up costs far less than finding it after.
Cracks in the old slab
Wide cracks or a low corner on an existing slab usually mean the base under it settled. If your addition will butt against it, we check it before planning the new one.
Damp spots on a floor
Damp spots or a musty smell on an older slab floor often mean there's no plastic under it or water running toward the house, and it rarely gets better by waiting.
What happens when you call about a slab foundation in Alexandria?
Call and I come look
You call, and I come out to look at the site and ask what's there now and what the slab has to carry. You get a written estimate that lists what's included.
Sort the paperwork, then pour
We work out which office covers your address and what paperwork the job needs before we set a pour date. Then our crew forms, places the steel and pours.
Walk the finished slab together
I walk the finished job with you and go over how long to wait before the slab takes weight. Your satisfaction, guaranteed.
Questions about slab foundations
These are the questions I hear most from Alexandria owners planning a new home or an addition. If yours isn't here, call or send the form and ask about your own lot.
How much does a slab foundation cost in Northern Virginia?
A reinforced concrete slab in Northern Virginia usually costs about $7 to $12 per square foot, not counting staining or stamping. That's the general market range, not our price, and your own figure depends on the slab's size, the site work and what the soil report calls for, which is why I write it up after walking the lot.
Do I need a permit for a slab foundation in Alexandria, VA?
Plan on one, because Alexandria requires permits for most construction and maintenance of buildings and structures, and its list names new buildings and structures. It doesn't name slab foundations by themselves, so the city's Permit Center at 703.746.4200 is the place to confirm how your job is treated, and applications currently go through its online system, APEX. We take care of the permit work for our part of the job and tell you up front if anything needs your signature.
Do I need a soil report before building a slab foundation in Alexandria?
For a new house, yes, because the city's posted policy requires a soil report signed and sealed by a Virginia licensed design professional before the permit is issued. The report recommends a foundation design and any soil fixes, and it notes problems such as expansive marine clay, a high water table, buried debris or uncontrolled fill. For an addition, the city lets you choose a sealed report or a foundation designed to the state's minimum soil load-bearing capacity, with a licensed design professional or their agent inspecting the soil before footings go in. That policy comes from an older city file, so check the current version with the Permit Center, and if you have a report, I want to read it early.
How long does a new concrete slab take before it can hold weight?
A new slab should be walkable within 48 hours, though concrete takes a month to fully cure. Waiting a week before heavier loads go on it is the safer plan, so leave that week in your schedule before anyone stacks lumber on it.
How do I keep radon out of a house built on a slab?
Start with the gravel layer and plastic sheeting under the slab, which radon guidance lists among the basic features builders should include. The gravel lets soil gases move freely under the house and the plastic blocks them from coming up. Virginia's health department says a properly installed passive system is thought to cut indoor radon by an average of 50%, and it advises testing soon after you move in and hiring a certified radon mitigator to add a fan if the level is 4.0 pCi/L or higher.
What license does a contractor need to build a slab foundation in Virginia?
Virginia licenses contractors as Class A, B or C, partly by the total value of a single contract or project. Class C covers jobs over $1,000 but less than $30,000, Class B covers $30,000 or more but less than $150,000, and Class A covers $150,000 or more. Alexandria's permit application asks for the contractor's state license number, city business license number and contact information, so ask whoever you hire for those up front.
Get a written slab foundation estimate
Send your address, whether it's a new home or an addition, and any soil report you have, and we'll reply within one business day. I'll set a time to walk the lot and write a free estimate, with no obligation.
Examples of slab foundation work
Other foundation and site work
Foundation installation
When your plans call for a basement or crawl space instead of a slab, our crew builds the footings and walls the house will stand on.
Learn moreConcrete parking lot building
If you're building a small commercial or rental property, a parking lot planned with the building pad gets its grades and drainage worked out once, for both.
Learn more