Wood rot, termite damage, and structural decay are the most common reasons homeowners in San Jose call a carpenter. Whether you have noticed soft wood at a sill, discovered damage during a pest inspection, or felt an unexpected bounce in your floor, this guide explains what you are looking at, how to tell one problem from another, and what repair actually means. The Santa Clara Valley's clay soils, seasonal moisture, and stock of older homes built from the 1880s onward make these issues a practical reality for many households.
This is a reference guide, not a sales pitch. By the end, you will understand the difference between dry rot and wet rot, how insects hollow wood differently than fungi do, what a floor joist actually carries, and the honest criteria for deciding whether a member should be repaired or replaced. You will also know which trades do which work, so you can assemble the right team for your home.
Dry Rot and Wet Rot: Not the Same Problem
Dry rot and wet rot are both fungal decay, but they behave very differently and demand different solutions. Dry rot is caused by a fungus that needs sustained moisture in the wood, typically between 20 and 60 percent moisture content. It does not require standing water or active leaks. Once established, dry rot spreads through the wood grain and can even travel across masonry to colonize new timber, which makes it the more aggressive of the two. Wet rot, by contrast, is a fungus that requires a persistent direct water source and stays localized to that wet area. In the Santa Clara Valley's climate, with winter moisture and the seasonal wet-dry cycle, dry rot is the more common culprit in older framing and siding.
The two look and feel quite different. Dry rot wood develops a distinctive cubical cracking pattern and becomes dry and crumbly, almost like a biscuit. Wet rot darkens the wood and makes it spongy and soft, almost pulpy. The danger with both is that the surface can look deceptively sound. Paint and finish can hold moisture against the wood beneath while appearing perfectly intact on top. A screwdriver or awl is the only honest way to find out what is underneath. Probing the wood, especially at sills, fascia, and the base of exterior trim, will reveal the true condition far better than appearance alone.
Termite and Beetle Damage, and How It Differs from Rot
Termite and wood-boring beetle damage look different from rot and progress differently. Termites hollow out the interior of a member along the grain, often leaving a thin shell of sound wood on the surface. You may see mud tubes built on masonry as termites travel from soil to wood. Wood-boring beetles, by contrast, bore through the wood and leave behind small round or oval exit holes and a fine powder called frass. Both types of insect damage can occur in the same timber as fungal rot, because the same moisture that invites fungi also attracts insects. A member can be hollowed by termites, rotted by fungus, and riddled with beetle galleries all at once.
Identifying insects and treating them is the work of a pest control operator licensed or registered in your state, not a carpenter. When you have a pest inspection done, the report will tell you what is present and what should be treated. From that point, the carpenter's job is to remove and replace the damaged wood. We work from the pest operator's findings, not from a new inspection of our own. The two trades are separate because the regulatory requirements and the expertise are different. Once the insects have been addressed by a licensed pest operator, we rebuild the structure with new wood.
Reading the Signs Before You Open Anything Up
Before you call anyone, you can do a simple walk-through to identify where decay might be hiding. Look for paint that blisters or peels at window sills and door thresholds, especially on the north or shaded side of the house. Press on exterior trim, fascia, and soffit with your thumb or a screwdriver handle. Sound wood will resist. Soft or spongy wood, or wood that yields under light pressure, is a sign of moisture and decay. Check door and window frames to see whether doors or windows have begun to stick, bind, or close unevenly, which can happen when the framing around them swells or warps. Inside the house, walk the floors and feel for soft spots or areas that bounce or flex more than they should, especially near exterior walls or under bathrooms.
Look for musty or earthy smells in enclosed spaces like crawl spaces, basements, or closets, which often indicate persistent moisture. Check deck boards for soft spots by stepping on them, and look at where a deck ledger bolts to the house, since that connection is especially vulnerable to moisture. None of these signs means you need an emergency repair. They mean the wood should be looked at soon and probed properly. Surface appearance almost always understates the true extent of decay. Wood can look relatively sound on the outside while being significantly compromised beneath the paint or finish. A thorough probe with a screwdriver or awl will show you what is actually there.
What Decay Does to a Floor, a Deck and a Wall
To understand what decay does to your home, it helps to know what each piece of wood actually carries. In a floor, the floor joists run perpendicular to the direction of the room and carry the weight of everything on that floor down to the sill plate and rim joist at the perimeter. The subfloor sits on top of the joists and distributes point loads across them. The sill plate is the horizontal member that sits on the foundation or rim joist, and it anchors the entire wall frame above it. In a deck, the ledger is the board bolted to the house that carries half the deck's weight back into the structure. Lose section in any of these members, and you lose their ability to do that job.
The progression is gradual and honest. As a member loses cross-sectional area to decay, it loses stiffness first. That is what you feel as bounce or flex in a floor or deck. The member is still carrying the load, but with less rigidity. Over time, as decay advances, the remaining sound section becomes smaller and the deflection greater. A floor that was stiff becomes noticeably springy. A deck ledger that was solid begins to move. These changes happen long before any structural failure. The point is to address decay while there is still plenty of sound wood to work with, not to wait until the structure is compromised. The connection where a deck ledger meets the house is worth special attention, because moisture there can go unnoticed and that connection carries a disproportionate share of the load.
Repair or Replace: The Actual Criteria
The decision to repair or replace a damaged member comes down to four things: how much sound wood is left, where the damage is located, whether the water source can actually be closed, and how the two costs compare once you account for access and finish work. If a floor joist has lost section to decay but still has at least two-thirds of its original thickness of sound wood, and the damage is not at a bearing point where it sits on the rim joist, then sistering (bolting a new joist alongside it) is often the right answer. The new joist carries the load, and the old one stays in place. If the decay is at a bearing point, or if less than one-third of the joist is sound, replacement is the honest answer.
For trim and non-structural profiled woodwork like casing or crown molding, epoxy consolidants have a real but narrow use. They can harden surface decay on trim that is worth saving for its character or cost. But epoxy filler over structural rot is not a repair, it is cosmetic postponement. A good contractor will quote you both options where both are real and explain the trade-offs. Repair costs less upfront but assumes the water source is closed and the remaining wood is sound. Replacement costs more but is permanent and gives you a warranty. If the moisture problem that caused the decay is not fixed, any repair will fail. That is why identifying and closing the water path is as important as the carpentry itself.
Who Does What: Carpenter, Pest Operator, Engineer
Protecting your home means understanding which trade does which work. A pest control operator licensed or registered in your state identifies insects and treats them. A carpenter (that is us, fully insured and EPA Lead-Safe Certified) removes and replaces damaged wood and closes the water path that invited the decay in the first place. A licensed structural engineer sizes beams, specifies repairs for load-bearing members, and provides the drawings and calculations that a building department requires. The building department permits and inspects structural work to make sure it meets code. Each of these professionals has expertise and legal authority the others do not have.
When you have a problem, start with a pest inspection if insects are suspected. Once you have that report, call a carpenter to assess the wood damage and quote repair. If the damage involves a load-bearing wall, beam, or major joist replacement, your carpenter or the building department may require a structural engineer to specify the repair. Contact your local San Jose building department to learn what permits are required for your specific work. They set the rules, and requirements vary. We can help you document damage for an insurance claim, but we cannot promise coverage or approve claims. By keeping these roles separate and clear, you get honest work and the protection of professional accountability. Call us for a free estimate on wood repair and to discuss which other trades you may need.