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Boral Home Additions & ADU: The West Palm Beach Owner’s Guide
Adding square footage to a Boral-built home in West Palm Beach typically costs between $45,000 and $130,000 for a ground-up addition, while a full ADU runs $90,000 to $220,000 depending on size, foundation work, and finish level. We’ve worked on Boral homes throughout Flamingo Park, El Cid, and Grandview Heights, and the concrete block construction Boral uses in South Florida changes how additions need to be tied in, flashed, and finished. If you’re noticing cracks along the seam where an old addition meets the main house, water staining at the roofline, or a door that suddenly won’t latch, you’re likely looking at a failed tie-in or settling issue, not a cosmetic problem. Those are the calls we walk most often in this market.
Most West Palm Beach homeowners discover the real problem when the first heavy rain of hurricane season shows up in the corner of a bedroom. Boral builds a solid shell, but every addition lives or dies on the connection points: the roof tie-in, the slab dowels, and the flashing where old block meets new block. When any of those fail, the fix is never a tube of caulk. It’s structural, and it needs a licensed contractor who knows how Boral’s block dimensions run and what the city inspector will be looking for.
Which Boral Models This Applies To
Boral’s South Florida footprint is mostly concrete block construction, and the homes we see in West Palm Beach follow two patterns: the original 1950s-1970s CBS ranches and the newer 1990s-2010s builds with Boral’s denser block and stucco finishes. The addition compatibility question comes down to block dimensions and lintel spans, not a model number. Older Boral block runs a true 8″ x 8″ x 16″ nominal, while some newer lines run 7-5/8″ actual height, which changes coursing alignment and the way a new roofline has to step off the existing plate.
Here’s the compatibility gotcha we see repeatedly in West Palm Beach: Boral’s accent and split-face block lines are dimensionally identical for stacking, but the mortar joint color and texture on a 40-year-old CBS wall cannot be matched from a new pallet. If the addition is visible from the street, you either commit to a full stucco skim coat on both old and new walls, or you accept a visible seam and adjust the design around it. We handle this by writing the finish plan into the scope before demo starts, so there’s no surprise in week four. For OEM versus aftermarket: Boral block is still manufactured and available through local supply yards in West Palm Beach, and for structural additions we specify new Boral block rather than substitutes. The block is the cheap part of an addition. The labor to set it is not, and nobody saves money installing a mismatched coursing height.
Styles & brands we work with
Signs Your Boral Home Additions & ADU Is Failing
- Vertical or stair-step cracking at the seam where the addition meets the original house. This is the classic sign of differential settlement between the original slab and the newer footing. It never fixes itself, and in West Palm Beach’s sandy soil it usually gets worse after a wet season.
- Water staining or efflorescence on the interior ceiling where the addition roof ties into the main roof. The flashing between old and new roof planes failed or was never flashed correctly. By the time you see the stain, the plywood sheathing underneath is usually soft.
- Doors or windows inside the addition that suddenly stick or won’t latch. The door frame is racking because the addition’s slab or lintel has moved. A door that latched fine for ten years and then didn’t is a structural symptom, not a humidity issue.
- A visible gap opening between the addition and the original house wall, inside a closet or along the exterior. You can sometimes see daylight through it. This is the tie-in failing and it needs an engineer’s look before it becomes a water and pest highway.
- Musty smell or mold at the baseboard of the wall that connects old house to new. That wall is wicking moisture from a failed flashing detail or a slab edge that wasn’t sealed. In West Palm Beach’s humidity, that smell means hidden rot within a few months.
See the difference
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After
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AfterReplacement Cost & What’s Included
In West Palm Beach, a full home addition tied into a Boral CBS structure runs $45,000 to $130,000, and an ADU on the same property runs $90,000 to $220,000. What drives the spread is simple: the size of the footprint, whether you’re on a crawlspace or slab, how much roof has to be cut and re-framed, and what finish level the interior gets. A 400-square-foot bedroom addition with a flat roof tie-in sits at the low end. A 900-square-foot ADU with a kitchen, bath, and separate electric service sits at the top.
Our written price includes the engineering stamps, the permit set, the demo of any failed structure, new Boral block to match, tie-in hardware, roofing membrane and flashing, stucco and paint, and interior finish carpentry. It also includes the Cedarwell Care Promise: drop cloths on every floor inside the existing house, shoe covers at the door, quiet tools during nap and school hours where possible, and a photo of the clean-up before the crew leaves. The 365-Day Done Right Promise covers the completed addition. If something isn’t right after we finish, we make it right. We also stock and install KraftMaid and Wellborn cabinets, Cambria and Silestone countertops, and Kohler, Moen, and Grohe fixtures if the addition includes a kitchen or bath.
DIY or Call Us?
You can safely document what you’re seeing: take photos of the cracks with a quarter or a ruler for scale, note the date, and check again after the next heavy rain. What you should not attempt to DIY is the actual tie-in repair. Cutting into a Boral block wall to add a new lintel or a roof ledger is a job for a licensed contractor. A poorly tied addition in South Florida is a wind-uplift risk during hurricane season, and a bad tie-in can fail in ways you won’t see until a storm finds it. The concrete and steel work also requires an engineer’s seal and a city inspection in West Palm Beach, and the inspector will want to see who did the work.
If the seam is open, if water is getting in, or if the addition is moving, call our office at (728) 203-3270. Graham Stein walks every job site himself before a single drop cloth goes down, and you’ll have a written scope in your hands before the first tool is unpacked. Put it in writing, then do exactly that.
FAQs
A properly tied and flashed addition on a Boral CBS home should last 50 to 80 years with routine maintenance, but the seam and the roof tie-in need an inspection every 5 to 10 years because West Palm Beach’s wet-dry-wet climate cycles stress those connection points harder than the rest of the structure. The original block will outlast the flashing almost every time. Call (728) 203-3270 if you want us to inspect a seam that worries you.
Yes, if the failure is caught at the flashing or lintel stage and the block itself is still sound, the addition can often be re-tied, re-flashed, and refinished without a full teardown. If the slab has settled enough to crack load-bearing block, you’re looking at underpinning or a partial rebuild. An inspection tells you which one you have. Call (728) 203-3270 and we’ll come look at it.
A straightforward bedroom addition runs 8 to 12 weeks from demo to final inspection, and a full ADU with kitchen and bath runs 4 to 6 months. The two things that stretch the timeline in West Palm Beach are the permitting queue and the inspection schedule, not the framing. We include a written start and end window in every scope, and we call when we say we will.
We source new Boral block from supply yards in West Palm Beach for every structural addition we build, and we keep the flashing, tie-down hardware, and stucco materials on order per project so we’re never waiting on a pallet mid-frame. For interior finishes, we install KraftMaid and Wellborn cabinets, Cambria and Silestone countertops, and Kohler and Moen fixtures for additions and ADUs that include kitchen or bath space. Call (728) 203-3270 to talk through your project and get a written price.
Written by Graham Stein, Owner, Elmstead Remodeling West Palm Beach at Elmstead Remodeling West Palm Beach, serving West Palm Beach and nearby areas.
