Home Addition Contractor Maintenance Schedule: What to Do and When

Home Addition Contractor Maintenance Schedule: What to Do and When

Most home addition warranties are voided not by bad workmanship, but by skipped maintenance tasks that never appear in the contract. A new addition built in Los Angeles goes through a five-year settling cycle that the original house finished decades ago, and the seams between old and new construction fail on a predictable calendar. This guide, along with our Home Addition Contractor Troubleshooting: Common Problems and How to Fix Them, gives you the exact schedule: what to check at 30 days, 6 months, 1 year, and every season after, with the specific fixes that keep your warranty valid and your addition dry.

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Quick Answer

A new home addition needs inspection at 30 days, 6 months, and 12 months after completion, then seasonal checks every spring and fall. The most critical items are the old-to-new foundation joint, roof flashing at the tie-in point, caulk seams around windows and doors, and HVAC air balancing. In Los Angeles, where the dry season and the rainy season each stress different parts of the addition, skipping the fall flashing check is the most common cause of leaks in years two through four.

Table of Contents

• Why the First Five Years Are Different
• The 30-Day Inspection Checklist
• The 6-Month Inspection Checklist
• The 12-Month Inspection Checklist
• The Old-to-New Foundation Joint: What Cracking Actually Means
• Roof Flashing at the Tie-In Point: Your Most Likely Leak
• HVAC Balancing After an Addition
• How to Keep Your Written Warranty Valid
• Common Mistakes to Avoid
• When to Call a Professional
• Frequently Asked Questions
• The Bottom Line

Why the First Five Years Are Different

Your original house settled years ago. The lumber dried, the foundation found its final position, and the caulk has long since cured into place. A new addition is a different animal. Fresh lumber carries moisture that evaporates over the first two to three years, causing walls to shift by fractions of an inch. New concrete continues to cure and shrink for years. Every seam between the old structure and the new one moves in ways the rest of your house no longer does.

In Los Angeles, the problem gets worse because of our climate pattern. We get long dry stretches where materials shrink, followed by sudden winter rain that makes everything swell. That repeated cycle works caulk beads loose and opens hairline gaps at flashing points. Homeowners in neighborhoods like Sherman Oaks, Eagle Rock, and Westchester deal with this every year. The addition doesn’t fail because it was built wrong. It fails because nobody told the homeowner to check the seams on a schedule.

What most Home Addition Contractor Warning Signs Every Homeowner Should Know articles miss: your written warranty assumes you’ll do basic seasonal maintenance. A skipped inspection is not automatically grounds for voiding a warranty, but if a small gap grows into a leak over two years because nobody looked at it, the contractor has room to argue neglect. The schedule below removes that argument.

The 30-Day Inspection Checklist

Thirty days after the final walkthrough is when the first wave of settling shows up. Run this list in the first month, ideally on a day with good light. Most of these items take under an hour. In our experience building additions around Los Angeles, the 30-day check catches roughly a third of everything that will ever need fixing on a new addition.

1. Check every window and door for sticking. As the new framing dries, openings shift slightly. A window that sticks now will usually be fixable with a simple adjustment, not a replacement.
2. Run a bead of water along the outside of every window and door. Use a garden hose at low pressure. Watch inside for any water penetration at sill corners.
3. Inspect caulk lines at the old-to-new wall junction. Gaps wider than a dime at any point mean the caulk is already failing and needs a proper elastomeric replacement.
4. Check baseboards and crown molding for separation. Small gaps under a 1/8 inch are normal and cosmetic. Gaps over a quarter inch need a carpenter’s eye.
5. Test every outlet and light switch in the addition. New circuits can have a loose connection inside a box that only shows up after the first month of use.
6. Walk the roof tie-in. If you can safely view it from the ground with binoculars, do that. Look for lifted shingles or visible gaps in flashing. If you cannot see it safely, call a professional. Roof work on a two-story addition is not a DIY job.
7. Run the HVAC for a full heating and cooling cycle. Listen for rattles, check for musty odors, and confirm airflow reaches every new room.

Document everything with photos. Date-stamp them. These photos are the start of your maintenance file, and we cover exactly how to use that file to protect your warranty in the section below.

The 6-Month Inspection Checklist

Six months marks the end of the first full seasonal shift. If your addition was finished in spring, you’ve now been through a Los Angeles summer. If it was finished in fall, you’ve been through the winter rains. Either way, the building has cycled through a full dry-wet or hot-mild transition, and the second wave of issues appears now.

1. Re-check the old-to-new foundation joint. This is the most important item on the list. Look for vertical cracks or a gap that has widened since the 30-day check. Gaps under 1/4 inch with no displacement are normal settling. Anything wider, or any crack where one side is higher than the other, needs a structural engineer’s opinion.
2. Inspect the roof flashing at the tie-in point. Six months of sun and rain are enough to reveal any flashing that was improperly lapped. Look for lifted edges, missing sealant, or water stains on the ceiling below the tie-in.
3. Check all caulk seams again. Caulk applied to fresh lumber often fails within six months as the wood dries and shrinks. Re-caulk any seam that has separated.
4. Look for drywall cracks at wall corners and above doors. Hairline cracks are normal. Cracks wider than a penny’s edge, or cracks that run diagonally from a corner, deserve attention.
5. Clean the HVAC return and check the filter. New construction generates dust. A clogged filter in month six is normal, but it needs changing before it strains the system.
6. Test GFCI outlets. Press the test button, then the reset button. Do this on every outlet in the addition.

If anything on this list looks wrong, call your contractor now rather than waiting for the 12-month mark. Small issues in month six become expensive ones by month twelve.

The 12-Month Inspection Checklist

The one-year mark is the big one. Many contractor warranties have a one-year workmanship clause, and this is your last chance to get minor defects fixed before that clock runs out. In Los Angeles, where the building code requires inspections at specific stages, the one-year check is also a good time to confirm all your permit paperwork is closed out.

1. Do the complete 30-day and 6-month checklists again. Compare your photos from both earlier inspections to what you see now. Document any worsening of cracks, gaps, or separation.
2. Schedule a roof inspection of the tie-in point. If you haven’t had a professional look at the flashing by now, do it this month. Year one is when improperly sealed flashing usually shows itself, and fixing it now costs a few hundred dollars versus thousands for water damage later. Roof work of any kind on a sloped Los Angeles roof should be left to a trained professional with fall protection and insurance.
3. Check the exterior siding or stucco at the old-to-new junction. Look for hairline cracks, especially at corners and around penetrations like vents or hose bibs.
4. Flush the water heater if the addition has its own. Not every addition does, but if yours was plumbed with a new unit, year one is the right time for a flush.
5. Run every faucet and check under every sink. New supply lines and drain connections can loosen slightly from the first year of use. Tighten what’s loose.
6. Verify the HVAC system is balanced. We dig into what balancing means and how to tell if yours is off in the HVAC section below.
7. Pull up your final permit paperwork. Confirm the final inspection was signed off. In Los Angeles, an open permit on a home addition will come back to haunt you when you sell.

The Old-to-New Foundation Joint: What Cracking Actually Means

The joint where your new foundation meets your old foundation is the single most misunderstood part of a home addition. Homeowners panic over hairline cracks that are completely normal, and sometimes ignore wide cracks that signal real trouble. Here is how to tell the difference.

A hairline crack, roughly the width of a credit card edge or less, running vertically along the joint, is normal settling. The new foundation is finding its final bearing point. This usually stops within the first 12 to 18 months. You can mark the ends of the crack with a pencil and check it every few months. If the crack does not grow past your marks, you’re fine.

A crack wider than a quarter inch, or a crack where one side of the joint is vertically offset from the other, signals differential settling. This means the new foundation is moving at a different rate than the old one, and that difference is stressing the structure. In Los Angeles, this happens more often on hillside lots, in areas with expansive clay soil like parts of the San Fernando Valley, and on properties near old riverbeds where the soil composition changes dramatically over short distances.

The expansion gap at this joint is the intentional space left between the old slab and the new slab to allow for independent movement. Check it every fall. In autumn, before the winter rains arrive, the ground is at its driest after the long Los Angeles summer, and any widening of the gap is most visible. If the gap has grown by more than 1/8 inch since the previous fall, document it and call a structural engineer, not a handyman. This is not a caulk-it-and-forget-it situation. The fix may be as simple as confirming movement has stopped, or as involved as underpinning the new foundation. Only an engineer can tell you which.

Roof Flashing at the Tie-In Point: Your Most Likely Leak

When we build an addition, the roof of the new structure ties into the roof of the existing house at a junction called the tie-in point. This is where the new shingles or tiles meet the old roof, and it is the single most common leak location on any addition, bar none. In our experience across Los Angeles, from Valley Glen to Leimert Park, years two through four are when tie-in flashing failures peak. The sealant degrades, the metal shifts slightly with the settling structure, and the winter rains find a way in.

What to check every fall, before the rains start:

• Look for lifted or curled shingles or tiles at the junction.
• Check that the metal flashing is still tucked under the upper course of roofing material, not exposed on top.
• Look for cracks in any visible sealant, especially at corner bends where two pieces of flashing overlap.
• From inside the attic, check the underside of the roof deck at the tie-in for dark stains or water marks.

If you see any of these signs, do not climb up with a tube of roofing tar. Roofing sealant applied on top of failed flashing is a temporary patch that fails again within a year. The flashing itself needs to be re-lapped or replaced. This is roof work at height, on a slope, and it is dangerous. A fall from a single-story roof can kill. A fall from a two-story roof is often fatal. Call a licensed roofing contractor or the original builder. If the original contractor is still within their warranty period, this is exactly the kind of defect the warranty covers. At Lodgewick ADU Builders home, our 365-Day Done Right Promise means we come back and make it right for free if a flashing failure happens within the guarantee period. That commitment is in writing before we start.

HVAC Balancing After an Addition

When you add square footage to your house, your existing HVAC system suddenly has more air to condition. Even if the system was sized correctly for the addition, which a good Home Addition Contractor in Los Angeles will verify, the airflow needs to be rebalanced so each room gets the right volume of air. This is not a one-time setting. It drifts as the new ductwork settles and seals cure, and it needs checking at the 12-month mark.

Signs your HVAC is out of balance:

• The addition runs 4 to 6 degrees warmer than the original house in summer.
• Some rooms get strong airflow while others barely get any.
• The system short-cycles, turning on and off more frequently than it used to.
• Your energy bill climbs noticeably after the addition, even accounting for the added square footage.
• You hear whistling at vents, which means the damper is too closed or the duct is undersized.

Balancing is done by adjusting dampers in the ductwork to push more air to the rooms that need it. A professional will measure airflow at each register with a hood and set the dampers accordingly. This is a half-day job that costs roughly $250 to $500 in Los Angeles, depending on access to the ducts. If the system is still struggling after balancing, the original equipment may simply be too small for the added load. Upgrading to a larger unit or adding a ductless mini-split in the addition is a $4,000 to $12,000 decision. Get the balancing done first. It solves the problem far more often than homeowners expect.

How to Keep Your Written Warranty Valid

Your contractor gave you a written warranty. Its validity depends partly on you. Every warranty for construction work, whether it is from a Home Addition Contractor or from a prefab manufacturer like Cover or Dvele, includes language about proper maintenance. The warranty covers defects in workmanship. It does not cover damage caused by neglect, and the contractor decides what counts as neglect.

Here is how to document your maintenance so a warranty claim can never be denied for neglect:

1. Take date-stamped photos at every inspection. Your phone does this automatically. Use it. Photos prove you were looking at the right things at the right time.
2. Keep a simple log. A spiral notebook works. Write the date, what you checked, and what you found. A Google Doc or a notes app works just as well.
3. Save receipts for any professional work. If you paid for a roof inspection, an HVAC balancing, or a caulking repair, the receipt is evidence of maintenance.
4. Report problems in writing, not just by phone. An email to the contractor with the date and the issue creates a paper trail. A phone call does not.
5. Do not attempt major repairs yourself. If you damage the flashing trying to fix it, the warranty claim becomes a fight you will probably lose. Document, then call the contractor.

For additions built with prefab components from brands like Mighty Buildings or Boxabl, the manufacturer’s warranty often has its own maintenance schedule. Read it. Some prefab warranties require professional inspection of specific joints at set intervals, and failing to do that is grounds for denial. Your contractor should give you all warranty documents at the final walkthrough. If they did not, ask for them in writing.

Common Mistakes to Avoid

• Waiting until something leaks to look at the roof. Tie-in flashing failures in Los Angeles show visible signs months before water enters the house. Check it every fall, whether or not you see stains. By the time water appears on your ceiling, the damage has been happening for a while.
• Caulking over failed caulk. New caulk does not bond to old caulk. If a seam has separated, dig out the old bead, clean the surface, and apply a proper elastomeric caulk. Skimming over the top just delays the failure by a few months.
• Ignoring small cracks because “it’s just settling.” Most small cracks are just settling. But every crack that widens, offsets, or runs diagonally deserves a professional look. The cost of an engineer’s opinion is about $400 to $600 in Los Angeles. The cost of ignoring a real foundation problem typically starts at $15,000.
• Assuming the HVAC system will just figure it out. It will not. Airflow does not self-balance. If you do not address it, you will overheat the addition every summer and blame the build when the real issue is a damper setting.
• Losing the warranty paperwork. Scan every warranty document the day you receive it and store the files in two places. A cloud drive is fine. A shoebox in the garage is not, because garages flood, burn, and get raided by rodents.
• Letting a permit stay open. In Los Angeles, an open permit on an addition shows up in the permit records when you sell. Buyers walk away from open permits. Confirm the final inspection was signed and the permit was closed before the one-year mark.
• Forgetting that a garage conversion is still an addition. If you converted your garage through a Garage Conversion Contractor in Los Angeles, the old-to-new junction is where the garage slab meets the house foundation. It needs the same seasonal checks as any other addition. Converted garages in Los Angeles are especially prone to rising damp at that junction because the original slab often lacked a vapor barrier.

When to Call a Professional

Some maintenance tasks are yours. Others belong to a professional, and knowing the difference protects both the structure and your safety. Call a licensed contractor when you see a foundation crack wider than a quarter inch or one side of the joint offset from the other. Call a roofer when the tie-in flashing is lifted, cracked, or showing water stains beneath it. Never walk a sloped roof yourself, especially not a two-story addition in Los Angeles where tile roofs are common and one wrong step sends you over the edge. Call an HVAC technician when balancing does not fix uneven temperatures. And call the original builder whenever something fails that should be covered by the warranty. ADU Builders in Los Angeles are required to stand behind their work, and a written warranty only helps you if you use it. Lodgewick ADU Builders offers free estimates in Los Angeles. Call (254) 602-5618 and a live person answers.

Frequently Asked Questions

The Bottom Line

A new home addition is not maintenance-free. It moves, settles, and weathers for the first five years in ways your original house stopped doing long ago. The schedule is simple: check at 30 days, 6 months, and 12 months, then every spring and fall. Focus on the foundation joint, the roof flashing at the tie-in, the caulk seams, and the HVAC balance. Document everything in writing and photos. Do the seasonal checks and your addition will settle into a stable, dry, comfortable part of your home. For more guides & resources, explore our blog. Skip them, and the first sign of trouble will be a water stain on the ceiling in February.

Written by Russ Delmar, Owner at Lodgewick ADU Builders, serving Los Angeles since 2010.