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IKO Home Additions & ADU: The San Antonio Owner's Guide
An IKO home addition or ADU in San Antonio typically runs $45,000 to $130,000 installed, depending on square footage, foundation work, and whether we're tying into existing roofing and siding or building freestanding. We stock the IKO-compatible framing, sheathing, and tie-in components needed to match your existing structure, and most planning-to-footings timelines can be scoped within a week of the first walkthrough. The way most San Antonio homeowners discover a problem is structural, not cosmetic: a wall that's not square at the corner, a roofline that doesn't drain where the new build meets the old one, or a door that binds within six months of the addition settling.
Here's the thing about additions in San Antonio that most guides won't tell you: our soil shifts. The clay-heavy ground across Bexar County expands and contracts with every rain and drought cycle, so a home addition has to be framed and tied differently here than it would be in, say, Phoenix or Dallas. If the new slab isn't engineered for that movement, the IKO-compatible wall assemblies will crack at the seams within the first two to three years. That's not a materials failure; that's a planning failure. We plan for it from day one.
We're an independent San Antonio remodeler, not affiliated with IKO directly. What that means for you: we can spec IKO-compatible components or recommend proven equivalents that hold up better in our humidity cycles, and we'll put whichever choice in writing before any work starts.
Which IKO Models This Applies To
IKO manufactures residential roofing, waterproofing, and building envelope products rather than a single "home additions" system, so compatibility comes down to matching the existing roof profile, eave height, and wall sheathing of your current home to the new structure. When we do an IKO home addition in San Antonio, we're typically working with IKO's Cambridge or Dynasty asphalt shingle lines for the tie-in roof, IKO's ice-and-water shield underlayment for the valley where old roof meets new, and IKO synthetic underlayments for the open framing before the roofing goes down.
The compatibility gotcha most homeowners miss: IKO shingle color lots vary slightly between manufacturing runs, especially on the popular Driftwood and Dual Black tones. Order a single bundle later for a small repair and you'll see the difference from the curb. For an addition, we order enough for the entire roof plane, not just the new section, so the old and new roof read as one surface. That's a detail we handle automatically, but it's exactly the kind of thing that separates a clean addition from one that looks patched.
The OEM-vs-aftermarket decision: for roof tie-ins and underlayment, we recommend staying with IKO or a certified equivalent because the warranty math matters. IKO's limited lifetime shingle warranty applies when the entire roof system is installed to their spec, including underlayment and ventilation. Skip the proper underlayment to save $400 and you've voided the warranty on a $45,000-plus project. We don't let that happen.
For the structural framing, sheathing, and interior finishes, we also work with KraftMaid, Cambria, and Silestone for the cabinetry and countertops that often finish out these additions. The framing gets spec'd to local code and our own standard, which in San Antonio means strapping, anchors, and tie-downs rated for the wind and soil conditions we actually get between Loop 1604 and the Hill Country edge.
Styles & brands we work with
Signs Your IKO Home Additions & ADU Is Failing
- Gaps at the tie-in point between old roof and new roof. San Antonio's temperature swings cause expansion and contraction at the exact point where the two roof planes meet, and if the flashing wasn't stepped and sealed correctly, water follows that line. You'll see a dark stain on the ceiling inside, usually within the first year.
- Cracks running diagonal from window corners in the new walls. That's settlement, and it's the most common addition problem we fix in this market. A hairline crack isn't panic territory, but a crack wider than a quarter-inch that keeps growing means the slab or the framing wasn't designed for our clay soil conditions.
- Doors that bind at the top corner or won't latch in summer. The door frame wasn't shimmed square or the framing dried and twisted after install. In an IKO home addition, this usually traces back to framing lumber that was too wet when it went up, which is common when builds happen in San Antonio's humid spring months.
- Water pooling where the addition slab meets the existing foundation. We see this a lot in Alamo Heights and Terrell Hills where older homes get modern additions. If the grading wasn't re-sloped after the pour, water sits at that seam and eventually works into the wall plate. You'll smell it before you see it: musty drywall near the floor.
- Shingle granule loss concentrated on the new roof section only. If the IKO shingles on the addition are losing granules faster than the original roof, the new section wasn't ventilated to match the existing attic. Heat builds up, the shingles bake from both sides, and the granules let go. That's a ventilation failure, not a shingle defect.
See the difference
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After
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AfterReplacement Cost & What's Included
A full IKO-compatible home addition in San Antonio runs $45,000 to $130,000. Where you land in that range depends on square footage, whether you're building on a slab or crawlspace, how much roof tie-in work is required, and whether the addition needs its own HVAC run or can share the existing system. Smaller bump-outs on the low end; full ADUs with kitchens and baths push toward the top.
Here's the breakdown you're actually paying for:
| Scope | Estimated Cost |
| Home Addition (per square foot, including framing and roofing tie-in) | $100 – $150/sq ft |
| Full ADU Construction | $90,000 – $220,000 |
| Garage Conversion | $30,000 – $80,000 |
| Kitchen addition (combined with home addition) | Add $14,000 – $45,000 |
| Bathroom addition (combined with home addition) | Add $9,000 – $28,000 |
Those numbers include the parts: framing lumber, sheathing, IKO underlayment and shingles for the roof tie-in, fasteners, house wrap, and the structural hardware San Antonio code requires for wind and soil movement. They include our labor from framing crew to finish carpenters. They include the written line-item price you approve before we buy a single 2×6. And they include the 365-Day Done Right Promise: if it's not done right, we make it right, backed in writing on every project.
What moves the price: site access matters more than people expect. If the addition is at the back of a tight lot in Beacon Hill with no alley access, we're hand-carrying materials and the labor estimate reflects that. Root and soil conditions from your lot's history change the foundation spec, and that changes dollars. We don't hide that in a change order later; we find it in the estimate phase and price it then.
DIY or Call Us?
Framing a home addition is not a DIY project, and anyone who tells you otherwise is selling you something. The structural, electrical, and roofing parts of an IKO home addition in San Antonio require permits, inspections, and work that will fail catastrophically if someone without trade training gets it wrong. A roof tie-in done poorly doesn't just leak; it can take a section of the original roof structure with it during a spring storm.
What you can do as the owner: document what you have now. Measure the existing roofline, note the IKO shingle color and approximate age, and take photos of the area where the addition will tie in. That gives you a real baseline when comparing quotes. Check the soil comments on your property survey if you have one; if it mentions expansive clay, say that on the call and we'll know you've done your homework.
Beyond that, let a crew that frames weekly in San Antonio handle it. Our framing is square, the roof tie-in is flashed right, and Luca Romano still walks every finished addition before we hand over the keys. Call (432) 547-6806 and we'll put a real number in front of you before any work begins.
FAQs
A properly built IKO-tied home addition in San Antonio should last 50-plus years for the structural framing and 25 to 30 years on the IKO roofing before the shingles need replacement, assuming the ventilation and flashing were done to spec. The weak points are always the tie-in seam and the foundation, not the materials. That's why we engineer both for local soil movement and inspect the tie-in annually after the build. Call (432) 547-6806 if you want us to walk your existing addition and tell you honestly how it's holding up.
Yes, in most cases. When we see a failing IKO addition in San Antonio, the fix is usually surgical: re-flash the tie-in, add strapping or shear panels, re-square a deformed door opening, or re-slope the grade at the foundation seam. Rebuilds are only necessary when structural movement has cracked the slab or separated wall framing from the foundation. We'll tell you which one you have after a walkthrough, and we'll show you the measurements that prove it. Estimates are free.
A roof tie-in repair on an IKO addition is typically a two to three day job for our crew. A full small addition, from slab to dried-in framing, takes three to six weeks depending on weather and inspections. Full ADUs run eight to sixteen weeks from permit to punch list. You'll get a written schedule with your written price, and photo updates at each key stage so you know exactly where things stand.
We stock the common IKO underlayments, ice-and-water shields, and the flashing profiles we use most on San Antonio tie-ins on our trucks, and we stage full IKO shingle orders at our supplier for the common colorways. If your addition uses a less common IKO shingle color, we'll order it ahead of the tear-off so you're never waiting on materials mid-job. This isn't retail parts sales; it's the supply chain we run for our own installs. Call (432) 547-6806 for an exact quote on your scope.
The craft comes first. Everything else follows. That's worked for Luca Romano and the crew across San Antonio for years, and it's the standard every IKO addition we build has to meet before we call it done.
Written by Luca Romano, Owner, Sawyer Remodel San Antonio at Sawyer Remodel San Antonio, serving San Antonio and nearby areas.
