Simonton Home Additions & ADU Nationwide | Barrett & Sons Construction

Simonton Home Additions & ADU: The Los Angeles Owner’s Guide

If you’re planning a home addition or ADU in Los Angeles and want Simonton-quality planning, the typical project runs $53,100 to $153,400 depending on square footage, foundation work, and finish level. We bring the same discipline to additions and ADUs that Simonton brings to windows – measured twice, spec’d once, and built to last. Most owners reach out to us after they’ve had a design drawn by someone who doesn’t understand Los Angeles setbacks, or after a previous contractor quoted a number that quietly left out the foundation pour.

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The symptom picture is usually the same: you’ve got a garage that’s too small, a lot that’s too big to waste, or an aging parent who needs a unit closer than a rental across town. What you’re really looking for is a builder who treats the permit counter like a place you visit, not a problem you avoid. That’s how Tom Barrett has run Barrett & Sons Construction since 1998, and it’s how his sons run their crews today.

Which Simonton Home Additions & ADU Projects This Applies To

Simonton doesn’t make home addition or ADU kits, and we’re an independent builder – not affiliated with Simonton. But the planning logic transfers: a Simonton window is engineered for a specific rough opening, and your ADU or addition deserves the same no-guesswork approach to framing, foundation, and roofline tie-in. We spec Simonton windows into most Los Angeles additions and ADUs because the Southern California sun and coastal air punish cheap frames within five years, and Simonton’s vinyl extrusion holds its seal far longer than builder-grade alternatives.

For project planning, the “model-number” equivalent is your lot. The compatibility check that matters: zoning designation (R1, R2, RD), front and rear setback requirements, and whether your ADU triggers a school-fee or parkland fee under Los Angeles municipal code. A specific gotcha: some hillside lots in Los Angeles require a geotech report before the city will even open your ADU permit. We handle that as part of the scope – in writing, before we start. We also stock framing-level planning across KraftMaid, Cambria, and Silestone for interior finish packages, so cabinet and counter decisions don’t stall the job mid-flight.

Signs Your Home Addition or ADU Plan Is Failing

• Your first quote didn’t include the foundation. This is the biggest red flag in Los Angeles additions. A design-build quote without a foundation allowance in writing is a surprise invoice waiting for its date. We write it all down before a single nail moves.
• The setback math doesn’t add up. If a builder tells you the city “won’t care” about that extra four feet, the city will care, and the inspector works for you, not for him. That’s why Tom likes the inspector.
• Your finish allowance is a single round number. A bathroom vanity allowance of “$3,000” without line items means you’re getting whatever’s left on the truck. We spec Cambria or Silestone counters and named cabinet brands so you know exactly what’s going in.
• The roofline tie-in wasn’t discussed. A bad roof connection between old and new is where Los Angeles rains find their way in. We cut back to solid sheathing and flash it like a new build.
• No one mentioned a geotech report for your hillside lot. If your ADU is on a slope and the plan skips the soil study, the plan is not ready for the permit counter. We handle that paperwork as standard on eligible jobs.

Replacement Cost & What’s Included

In Los Angeles, a home addition runs $53,100 to $153,400; an ADU in the backyard runs $106,200 to $259,600 when it’s built as a separate structure. What drives the range: foundation type (slab versus raised), whether you’re tying into existing plumbing and electrical or running new lines, and how much of the interior finish we’re doing. A garage conversion lands at $35,400 to $94,400 because the shell already exists.

Every Barrett & Sons contract includes permits pulled, inspections signed, a written change order before any scope change touches the job, and our 90-Day Done Right Promise. On top of that, every home addition in Los Angeles gets the lines in writing: scope, allowances, and any price change – all on paper before work happens. Call (877) 610-1318 for a free estimate, and we’ll send the numbers in writing.

DIY or Call Us?

You can safely check a few things yourself: pull your parcel map from the Los Angeles County Assessor’s site, measure your rear yard depth to the inch, and confirm your zoning designation online. Those three facts will tell you whether an ADU is even possible on your lot, and they cost you nothing.

What you shouldn’t do is start trenching, framing, or tying into your panel on a permitted addition. Electrical panel and gas-line work on an ADU is dangerous, period – we recommend a trained professional for anything behind the meter or under pressure. Tom Barrett grew up in the San Fernando Valley, not far from the old stretch of Van Nuys Boulevard where his dad used to take him to watch crews pour foundations on weekends. He learned the trade at Los Angeles Trade-Technical College, and he’ll tell you the same thing he tells his sons: the job never lies. If a stud wall is crooked, you fix it before the drywall goes up. Call (877) 610-1318 and we’ll come look at your lot.

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