Decks are beautiful and functional, but they come with their share of risks and costs. The biggest: dry rot. While certain woods — redwood, mahogany, cypress, cedar, and pressure treated wood — are less likely to rot to begin with, anyone with a deck or aspirations to build one needs to be versed in the warning signs and mitigation strategies for dry rot. Here are your must-knows:
What's Dry Rot?
Dry rot is a fungus that weakens the wood in your deck. After some time (sometimes as little as two years), you may notice that your wood will become discolored, get spongy, and come apart when wet. That's dry rot. The main causes are moisture and insects, which leave wood susceptible to microorganisms that eat the cellulose that binds its various layers together. The result: as the cellulose disappears, the wood becomes frail and falls apart. Look for areas with insect damage, where water pools, or that are more exposed to moisture such as posts that contact the ground. Also check for sources of leaky water: faulty sprinklers, plumbing, or gutters.
Pro tip: An easy way to test your deck for dry rot is to poke it with a screwdriver. If the screwdriver won't go in more than one eight of an inch (without brute force — dry rot is soft), you're in the clear.
The Good: Pre-emptive Weatherproofing
As with most situations around your home, dry rot doesn't necessarily spell a deck disaster straight away. You'll start off with moist wood which has not developed dry rot yet. This is when you can avoid more troublesome issues down the road by addressing the source of moisture (identify and fix leaks), drying the wood, and treating it with a sealer and/or stain to stop moisture from finding its way in again. Cleaning your deck will also help keep it free of dirt, debris, and mildew, which look bad and encourage water retention. This is the cheap end of the spectrum. Cleaning and sealing a deck is regular maintenance and typically costs somewhere around $120 to $250 for pressure cleaning, and up to $500 for sealing and/or staining depending on size and condition. This is something you can do yourself in a day or have a House Manager knock out in a few hours.
The Bad: Deck Repairs
Alright, your deck has fallen prey to dry rot. Don't panic just yet. Chances are, it hasn't spread to all of the wood and repairs won't be too pricey. First thing's first: we need to figure just how extensive the damage is. Most rot occurs in areas that aren't easily visible: the ledger board, under the deck boards, and under tread stairs. Some pieces will clearly be rotting, but inspect adjacent pieces closely. Spending a weekend replacing rotten wood only to have dry rot return months later is the worst! If you're at all unsure which pieces can stay, get professional help. Pricing varies depending on the kind of wood and the extent of damage, but you can expect to spend at least $700 and up to $3,000.
Pro tip: Be particularly careful when checking the ledger board — the strip of wood that connects the deck to your house. Mis-installed ledger boards lead to some of the most common and serious issues. Since your house framing isn't treated for moisture, it's vulnerable to rot. If this particular spot gets infected, you'll have to replace the entire deck and possibly part of the wall.
The Ugly: Full Replacement
Unfortunately, some situations are simply beyond repair. According to Pro Remodeler, the key here is determining whether your deck is simply failing (deteriorating but still safe) or about to collapse. If only one or two of the posts show signs of rot, you may be able to get away with replacing them without further work. Joists, which are structural pieces of wood that hold your deck up, are trickier to replace without taking the entire deck apart. If your frame is fine and only the decking is rotting, you may be able to reuse parts of the frame and replace the deck boards. As you can see, there are a number of possibilities here. The important things are getting rid of all of the rot and making sure your deck is still safe. In these situations, it's usually best to go with a professional. On average, full replacements start around $3,000 for small decks (less than 200 feet), and can go up to $45,000 for fancier materials, designs, and story installs.
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We promise it's not all doom and gloom with decks! Dry rot sounds terrible, but a little maintenance goes a long way here. If you haven't taken a close look at your deck recently, do so this weekend. Even if you find some damage, you can save yourself hundreds or thousands of dollars by taking care of it now so you can enjoy that gorgeous deck worry-free.
