Carlsbad Concrete Group stands as San Diego County's leading specialist in ADU and addition foundations, specializing in slab-on-grade foundations, continuous wall footings, and thickened slab edges under bearing walls. We offer raised floors on isolated footings and grade beams for sloped lots.
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Our team provides vapor retarder and under-slab prep, delivering a level, dry base for homes and inspection-ready footings for both residential and commercial projects. Backed by 11 years in business and our 1-year workmanship warranty, we've completed over 1,460 projects, from a one-room bump-out at the back of a house to a detached two-bedroom backyard cottage.
From anchor bolts placed at the spacing on the structural sheet to hold-downs at every shear wall end, our team handles every detail. Serving Carlsbad and neighboring Harmony Grove, Lake San Marcos and Encinitas, we book the foundation inspector before we ever book the concrete truck.
Request a free estimate with your plan set, and our estimator will read the foundation sheet and walk the lot with you.
What you can hold us to
Jason, Harmony Grove Village, Harmony Grove
A detached ADU planned at the back of a newer lot, with plumbing set before the pour
Investment and duration figures are estimates. Your written quote sets the final price and schedule.
Jason in Harmony Grove Village now has a 780 sq ft ADU slab that passed its foundation inspection the first time and was ready for framing the following week. His plan called for a detached ADU at the back of a newer lot, with the plumbing set before the pour, so we laid out the footings from the engineer's sheet and had the under-slab drain lines inspected while the trenches were still open. The foundation is slab-on-grade with thickened footings and a vapor barrier, poured over a compacted base with rebar tied on chairs and a deepened perimeter footing under the bearing walls. The work was an estimated $9,200 to $12,800 and took an estimated 4 to 7 days from layout to stripping the forms, and the inspector was booked before the truck was called.
An ADU or addition foundation in Carlsbad is poured only after the building inspector signs off the trenches, forms and steel, and we never schedule concrete before that card is signed. The California Residential Code calls for the foundation inspection once the trenches are dug, the forms are set and the reinforcing steel is supported in place, and before any concrete is placed. Under-slab plumbing, gas and electrical rough-ins are inspected before they are covered, which on a slab foundation means before the pour.
A missed sleeve or a misplaced bolt after the pour means saw-cutting and drilling into a brand new slab, which is why this order never changes.
Your structural engineer, not our crew, chooses between slab, footings and piers after reading the soil and the slope, and each option gets its own inspection checklist. Most North County ADUs on flat lots in Lake San Marcos and Harmony Grove go slab-on-grade, while sloped lots near Elfin Forest often need a raised floor on footings or grade beams.
| Foundation type | Where it fits | What gets inspected |
|---|---|---|
| Slab-on-grade with thickened edges | Flat, firm lots and most detached ADUs | Footing depth, vapor retarder, rebar on chairs, under-slab plumbing |
| Continuous wall footings | Room additions tied to an older raised-floor house | Trench width and depth, steel, anchor bolt spacing |
| Raised floor on isolated footings | Sloped lots and crawlspace access for utilities | Pad sizes, post bases, hold-downs |
| Grade beams on piers | Hillside lots where the soils report asks for depth | Pier depth, beam steel, engineer's observation letter |
An attached addition meets the old house at the floor height and with the connection the engineer details, and we follow that detail exactly. Extending a slab-on-grade house is the harder case, because the new slab has to finish level with the old one, and an old slab cannot simply be lifted to match. In older La Costa and Olivenhain homes we also protect the stucco, the landscaping and the existing footing while the trench runs beside it. Dowels drilled and epoxied into the old footing are placed only where the plan shows them.
Footings, vapor barrier, rebar and a slab-on-grade, about 600 to 1,000 sq ft
Demolition, haul-off, compacted base, rebar and a broom or exposed finish for a 2-car drive
Integral color, a stamp pattern and release, sealed after cure, about 400 sq ft
Tear-out around the coping, new base and steel, a cool broom, salt or exposed finish
A poured cantilevered wall with footing, steel and drainage behind it, about 50 linear ft
Rough-sawn board forms leave the wood grain in the face, about 200 sq ft of wall
Investment and duration figures are estimates. Your written quote sets the final price and schedule.
An ADU or addition slab foundation in Carlsbad is estimated at roughly $3,600 to $14,000 for about 600 to 1,000 sq ft of slab-on-grade, and the footprint, the footing depth on the plan and the soil move the price most. The table splits that range by the jobs we pour most often.
| Foundation job | Est. investment | Est. duration |
|---|---|---|
| ADU or addition slab foundation (600 to 1,000 sq ft) | Est. $3,600 to $14,000 per project | Est. 3 to 7 days |
| Small room addition slab with tie-in dowels | Est. $3,600 to $8,000 per project | Est. 3 to 5 days |
| Detached ADU slab with thickened footings | Est. $7,000 to $14,000 per project | Est. 4 to 7 days |
| Garage conversion footing and slab infill | Est. $3,600 to $9,000 per project | Est. 3 to 5 days |
A sloped Elfin Forest or Poway lot typically lands near the top of these ranges, because cut and fill, a line pump and deeper footings all add labor. Old patio or slab tear-out is quoted as its own line when it sits where the ADU will go.
These foundation figures are estimates for Carlsbad and nearby cities, and they are subject to change. Your written quote after we read the plans and walk the lot sets the final price and the pour schedule, and it depends on the footprint, the soils report and the access for the truck.
The foundation is plain gray structural concrete, but the flatwork around a new ADU is where finishes come back in. Owners often add an entry walk or garden path from the main house, or set the path to a new unit in stamped and decorative concrete to match an existing patio, and broom-finish concrete typically runs $6 to $13 per sq ft installed for that walk.
Our owner reads every foundation sheet before it is quoted, and our estimator flags any detail that needs an answer from your engineer before the trench is dug. The same foreman who sets the anchor bolts is on the slab for the pour, and the 1-year workmanship warranty covers the foundation from the day the concrete is placed. Our crews have poured 1,460 projects across a 35-mile radius, and builders and owner-builders call us because the inspection card gets signed on the first visit.
We pour ADU and addition foundations across North County, with most new units going in on the larger lots of Harmony Grove, Lake San Marcos and Poway, and backyard cottages behind 1950s homes in Carlsbad Village. Encinitas, Elfin Forest, Bonsall, Rancho Santa Fe and Fairbanks Ranch are covered too, and every city is on our service area list.
A hillside ADU often needs an engineered retaining wall to make room for the pad, and an older main house with a sticking door may need slab foundation repair before the addition ties into it. Because a new tenant brings a car, some owners have us pour an RV pad or side-yard slab while the crew and pump are already on site.
An ADU slab foundation is estimated at roughly $3,600 to $14,000 for 600 to 1,000 sq ft, and your written quote sets the final price after we read the plans.
Most ADU and addition foundations take an estimated 3 to 7 days on site, from layout and trenching to stripping the forms.
Yes, the approved plan set and any soils report decide the footing sizes, so we quote from the foundation sheet rather than a guess.
We book it, meet the inspector on site and make any correction before the concrete truck is scheduled.
Yes, we follow the connection your engineer details, with dowels or a new footing exactly where the plan places them.
Framing typically starts after about 7 days of curing, and heavy deliveries wait longer when the slab is still young.
Our deposit is no more than 10% or $1,000, whichever is less, and the rest comes as progress payments while the work is done.
Yes, we pour across a 35-mile radius, including Harmony Grove, Lake San Marcos, Poway and Bonsall.
Call us or request a free estimate, and we will read your foundation sheet, walk the lot and give you a written, itemized quote with the pour date.
Start to finish
We measure the area, shoot the grades and check drainage before anything is quoted.
The quote names the tear-out, base, reinforcement, finish and control joint layout.
The subgrade is compacted and the forms and rebar are checked before the truck is booked.
The crew places, finishes and cuts the joints, then walks the cured work with you.
Where we work
Call us or send the form, and we will book a site walk and measure the job.
Calls only, we do not receive text messages.
