L Square Design & Build
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L Square Design & Build operates as a rare thing in the ADU space: a genuinely integrated design-build firm where architecture, structural engineering, permitting, and construction all happen under one roof. Founded by Brian Leung, a UCI MBA and CSLB-licensed general contractor, the studio positions itself around a single principle: one team, one contract, one point of accountability for your entire project. This matters more than it sounds. Most ADU projects hand off between architects, structural engineers, permit expeditors, and separate contractors, each introducing their own timelines and communication gaps. L Square's model keeps your project moving as a single unit, with direct accountability that makes it harder for problems to slip through cracks.
The studio has completed over 200 ADU projects across Orange County and Los Angeles, serving communities from Laguna Beach to Long Beach, from Newport Beach to Anaheim Hills. Their service area spans a genuinely wide geography, but the firm maintains its core in Santa Ana with a roster of architects and engineers who stay engaged with each project from the initial sketch through final inspection. The team includes Kiko Zhou, an interior designer and California real estate agent who brings both aesthetic expertise and local market knowledge to each build. This combination of in-house design talent and on-site construction management means decisions get made faster and with better continuity than outsourced workflows allow.
L Square offers four engineered floor plan models as starting points: The Laguna (a compact studio), The Balboa (a one-bedroom), The Tustin (a two-bedroom), and The Newport (a second two-bedroom option). Each is customizable rather than fixed, so your ADU can adapt to your property's specific constraints and your family's needs. The firm also handles detached ADUs, attached additions, garage conversions, and junior ADUs (JADUs), the smaller format now allowed by California law. Properties with large lots are ideal candidates for detached units that sit independent of the main house, offering maximum privacy and rental appeal. Properties with smaller footprints or tighter zoning constraints might work better with garage conversions or attached additions that expand the footprint without using more land. L Square has completed projects across both categories and can assess your property's realistic options during the initial consultation.
The process unfolds over seven stages. The first week includes a consultation and site visit where the team understands your property, your goals, and what the local permitting environment actually allows. Weeks two through five focus on design: the team develops your custom floor plan, handles structural engineering, and prepares permit-ready drawings. From week five onward, L Square manages permitting (typically weeks five through thirteen depending on the city's processing time), then moves into construction over the next several months. The build itself usually runs three to eight months depending on complexity and weather, followed by final installation and handover. This timeline isn't arbitrary; it reflects the firm's experience across over 200 completed projects across different Orange County and LA jurisdictions. Permitting is the longest stage because it's entirely in the city's hands, but L Square handles the whole process in-house, which avoids the delays that come from back-and-forth between separate permit expeditors and contractors.
Pricing starts around $280 per square foot, though this number is genuinely site-dependent. A property with easy utility access, stable soil, and straightforward permitting will land at the lower end. Difficult sites, where you need extra foundation work or the city's review process is thorough, can run higher. L Square emphasizes that they provide free consultations and online cost estimates without obligation, which is worth taking them up on if you want a real number for your specific property. The firm's FAQ acknowledges this honestly: permitting timelines vary by city, utility costs depend on what's already available on your site, and construction schedules shift based on seasonal factors. Saying so up front is more useful than a headline number that only holds on an easy lot.
L Square's approach to design customization is instructive. The studio operates under a principle that the "permit-ready bones" stay engineered and consistent (saving time and cost), while "walls move and finishes change" based on your preferences. This means you're not locked into the four base floor plan models exactly as shown; instead, licensed architects draw each unit around your specific lot, natural light, privacy requirements, and how you actually want to live in the space. Interior finishes and appliances are hand-picked and integrated, so the unit arrives move-in ready rather than with bare walls and generic selections. This approach combines the speed and cost efficiency of pre-engineered solutions with the personalization of custom design, a sweet spot most ADU builders struggle to achieve.
What sets L Square apart from smaller residential builders and different from the prefab ADU companies is the hybrid approach. You get a custom design tailored to your property and preferences, not a fixed national model dropped on your lot. You also get genuine expertise in local permitting (a huge source of delays and rework in other firms), and you get someone who stays accountable through construction rather than disappearing once permits are approved. The firm's emphasis on "one team" serves to eliminate the finger-pointing that happens when a permitting firm, an architect, and a contractor are all different entities. At the same time, L Square is smaller and more localized than the national players, which means faster decisions and a team that knows Orange County and LA jurisdictions specifically.
For homeowners in Orange County or LA who want an ADU built quickly and want to minimize the risk of miscommunications, rework, or timeline slippage, L Square's all-in-house model is the more expensive insurance policy you might actually want. If you know your property inside out and have a clear picture of what you need, their free consultation and estimate process will tell you whether the timeline and cost align with your expectations. Two hundred completed projects across Orange County and Los Angeles is enough volume to have met most of what a permit counter can throw at a build. Homeowners ready to start the process can reach L Square via their website to request an initial consultation and cost estimate tailored to their specific property.
Keeping design, engineering, permitting and construction under one roof is the part worth paying for here. On a split team, the drawings get handed to a contractor who did not draw them, and the gap between what was designed and what can actually be built on your lot surfaces halfway through framing, when changing it is expensive. L Square carries that risk itself, which is why its per-square-foot number sits above the cheapest quotes you will collect. The trade is fewer change orders and one company answering for the schedule.
The free consultation and online estimate are the right first step even if you end up building with someone else. You get a real number for your own parcel, with your own utility situation and your own city's review process priced in, rather than a range pulled from an average. For an Orange County or Los Angeles owner deciding whether an ADU pencils at all, that is the question that needs answering before anything else.