Are you facing the dilemma of waterproofing a wood deck after it has been built?
It's an easy thing to overlook during the design stage as you are usually so focused on all the great things you are going to be doing on the deck area above.
It's not until you think about walking underneath your deck that you soon realize its wasted space unless it's dry.
Of course, the kind of decks I am referring to are second-level decks with enough useful space below them that it makes sense to waterproof the top of the deck.
The typical problem is a traditional wood surfaced deck with 2x6 or 5/4" decking boards. Actually, the decking could also be composite deck boards, but in both cases, the boards have gaps between them, and water drips through to the ground below.
So, where do you begin to fix this problem?
Four General Types of Solutions
There are several ways to create waterproof a deck.
There are either coatings, membranes, or physical catchment systems like eavestrough but much more evolved. Each has its own benefits and drawbacks.
I am going to talk about three types of solutions: waterproof deck coatings, membranes, locking deck boards, and catchment systems or under waterproof deck options.
Just as it sounds you cover the deck surface with a liquid material
and it becomes an impermeable layer. But it won't work directly on
gapped boards. You have to cover the boards with tongue and groove
plywood, glued and screwed to the deck.
But this is a project the average Do It Yourselfer could handle because the skill and cost required is low.
The types the you will find most often are liquid rubber products,
fiberglass resins and matting and in some professional circles, cement
For a much more detailed discussion see this article on deck coatings.
Membranes are solid sheets of waterproof material that are adhered
down onto surfaces much like flooring. The decking industry uses a lot
of durable vinyl flooring which originated in the boating industry to
seal the inside deck of a boat.
Turned out it was also a perfect way to seal wood surface decks. But
again, you have to use a plywood substrate. So its a bit more
challenging they welding is critical. So not the easiest for a DIYer.
If you see this as an option you should read the articles on vinyl membrane solutions.
A concept that is proven is to use extruded aluminum planks that
replace wooden boards. These extrusions lock together and can have a
textured, or profiled surface which stops water from dripping down and
channels it to the perimeter of the deck if the slope is correct.
Aluminum waterproof solutions like this also offer you some of the
longest lasting decking solutions possible. So you solve two solutions
at once. Not bad.
Here are the top options in this category that come to mind:
Under Deck Systems
Thankfully some very talented people have spent a lot of time working
out all the details of making a wood deck waterproof. They all are
based on physically catching water under the deck with panels that act
like a big eaves trough.
The run off water is channeled to another trough that takes the waters to a down spout.
Here are the ones that first come to mind for me:
These products really make all the space under your deck useful living space. And they can be easily added on to an existing deck as a retrofit.
Think of the utility you will gain by covering that area with a waterproof deck surface above your head and still having the beauty of a traditional wood framed decking surface.