wet rot vs dry rot

Is There a Difference in Dry Rot vs. Wet Rot on My Pier and Beam Home?

You’re wondering what dry rot vs. wet rot means for your home. Is there or what’s the difference between dry and wet rot on a wooden pier and beam foundation? If there is a difference, then do we do anything differently to repair the issues in the crawl space? 

Anchor Foundation Repair Bryan College Station

At Anchor Foundation Repair, we have been crawling pier and beam homes and assessing repair situations for 35+ years. We can tell you what’s really important about dry rot and wet rot, and that lies in the repairs more than in the cause.

In this article, we will outline the main differences between dry and wet rot. Then we discuss what needs to be done to repair these issues in your pier and beam or crawl space foundation and how to prevent rot conditions from recurring.

Dry Rot vs. Wet Rot: What’s the Difference?

Yes, there are some technical differences between dry rot and wet rot. As a service to you, I Googled a reputable answer to verify the info so that you don’t have to look elsewhere. I’ve summarized it all below . . .  I’m helpful like that sometimes . . . you’re welcome . . . 

wood damaged by dry rot
Dry Rot

Similarities of Dry Rot and Wet Rot

The first thing to know is that both dry rot and wet rot are wood decay conditions caused by moisture-activated fungi growth. These funguses are normally dormant and already present in the wood but the moisture just *brings them to life*. 

Don’t ask me why one is called dry rot but still caused by moisture, that’s just going to have to be a lifelong mystery for both of us . . .

Main Differences in Dry Rot vs. Wet Rot

wood damaged by wet rot
Wet Rot

What determines the difference between dry rot and wet rot are the amount of moisture needed for growth activation and the type of fungus. 

Dry rot is caused by one fungus (Serpula lacrymans, if you really want to know) that reacts and grows at lower moisture levels, around 20% humidity. Wet rot is caused by another fungal spore (called Coniophora puteana, if you’re curious) that requires higher moisture/humidity levels near 50% for growth to begin.

What Dry Rot and Wet Rot Mean for Your Home

damaged wood

The exact name of the fungus and the moisture level percentages are not that meaningful to most homeowners and their foundations. What’s more meaningful is that dry rot (surprisingly) has the potential to cause more widespread and extensive damage than wet rot. 

Probably because the lower moisture levels needed for dry rot can go undetected for longer periods. Whereas with wet rot you’re more likely to notice faster and can be more isolated due to leaks from specific water sources or heavy drainage problems. I’m no *science guy* but as a foundation guy I know this is true because I’ve seen it time and time again.

Ultimately, no matter what kind of rot you have, you’ve got to do two things to remedy the situation fully:

  1. Remove and replace the rotted wood, and
  2. Correct your moisture problem source(s).

If you think you have rot of any kind, it’s important to act quickly and be proactive with repairs and prevention. Wood rot can become more costly and catastrophic with prolonged inaction.

Repairs for Dry Rot and Wet Rot in a Crawl Space Foundation

wood rot from pluming leak

Because of the complex nature of crawl space foundations, any number of *wood parts* could fall victim to whichever rot you’ve got going on. Here’s a rundown of what it takes to replace the different interconnected structural components.

Side note: If you have an active plumbing leak causing wet rot, you should get the leak stopped and repaired first before moving on to the wood replacement.

Replacing Sill Beams

Any type of sills that are rotted should be fully removed and replaced in the same position to maintain the appropriate structural support. Sill beams are the first layer of large timber that serve as perimeter and load-bearing horizontal supports on top of ground penetrating piers

Sill replacement can be done by accessing the crawl space underneath the home. A temporary sill beam and jacks are set to carry the load normally held by the original sill, then the damaged beam can be safely removed and replaced in the correct location.

house leveling process

Replacing Floor Joists

Most of the time, instead of replacing floor joists, more are simply added. A technique called “sistering” is used and it basically means that a new joist is added alongside the damaged one and they are joined together.

The idea is to strengthen support for the subfloor and there’s no real need to take out the old ones if you just add in more.

Replacing Subfloor

replacing damaged subfloor
Subfloor removal and replacement

When the subfloor needs replacing, you can also add in extra joists in between existing joists, but that just buys you time. If the subfloor is truly decaying due to rot, no amount of extra joists will save it forever.

Replacing subfloor is an extensive project that requires a complete tear out and rebuild of the foundation and floor support structure. This is done by cutting out the floors from the top down from inside the home. 

You typically would have to move out or not be able to use the room or rooms for an extended period where subfloor replacement is needed. Extra costs are incurred with this large of a project because you might have to find alternate living arrangements and flooring replacement is likely necessary in the affected areas.

Preventing Wood Rot After Foundation Repairs

replacing rotted wood

In addition to replacing all the rotted wood, you also need to identify the moisture source or sources. Moisture and humidity in a crawl space could have one or more causes acting together to create the problem. 

Don’t assume it’s going to be just one issue that needs solving and then you’re done. Evaluate and explore all possibilities. Excess moisture and humid conditions under a pier and beam or crawl space home can come from:

  • Ground vapor due to low clearance crawl space,
  • Poor under-home ventilation,
  • Constricted airflow due to skirting material,
  • Poor ground drainage around the home,
  • Grading issues,
  • Non-existent or faulty gutters,
  • Lack of downspout extensions,
  • Leaking plumbing fixtures,
  • Rusted cast iron drain lines,
  • Water under the house that can’t drain out (need for a sump pump),
  • Or a combination of several of these factors.

Yes and sorry, this is a long, exhaustive list. Just tryin’ to be thorough! I suggest working first on the active flowing water sources like testing for plumbing leaks and gutter issues. Then move to grading and ground drainage problems. Lastly, consider airflow issues with changes to ventilation and skirting.

preventing wood rot with ventilation
Vents for airflow in a pier and beam home

Sump pumps are the *save for last* sort of solution that only works in some instances and I would try other solutions first.

Also, if a home is simply too close to the ground, elevating the whole house is a possibility only in some cases and should be done at the same time as the wood replacement. Here’s an article that discusses situations where whole home elevation might be a good idea.

Working through drainage and moisture issues is a long *trial and error* process. But it’s important to maintain dry conditions under your home. Ultimately, a dry crawl space is best for preventing both kinds of wood rot from occurring again, as well as other foundation settlement issues from developing.

Getting Started on Getting Rid of Wood Rot

Dry rot . . . wet rot, it doesn’t matter which kind of rot you’ve got. (Watch out, I might be a poet.) The bottom line is that wood rot doesn’t go away on its own and could get worse. Now you know it’s more important to act quickly to get rid of rot rather than worry too much about the exact spore causing your issue. 

crawl space home damaged wood

Address suspected rot of any kind right away with wood replacement and moisture mitigation.

At Anchor Foundation Repair, we’ve been replacing wood and working on crawl space foundations for 35+ years in BCS and beyond. We can replace wood under a home with one eye shut and our hands tied behind our backs – just kidding, we won’t try that on your house . . .

Ready to do wood rot repairs right the first time? To get your quoting process started, call 979.690.2020 during business hours, or use our online contact form 24/7 to avoid the phone tag hassle.