There are several different ways to finish the substructure of a composite deck. Installing composite fascia board is one of the more popular, providing a consistent finish both in appearance and maintenance with the decking.
But adding this additional layer on the rim and end joist raises an important question. Should deck boards overhang fascia?
Best practise, deck boards should overhang fascia plus a small reveal. Covering the top of the fascia plus extending past, providing a small reveal, nosing of between a ½” (12mm) to 1 ½” (38mm) depending on the decking material used.
With wood decking, the standard practice is an overhang of 1 ½’ to 2″ (38-50mm) past the rim joist. Providing enough overhang to cover the fascia board and that small gap between the rim and fascia board. But more on that later.
Composite decking, the more common deck with additional fascia board, is not so straight forward. As composite boards vary in allowable overhang. From flush to 2″ (50mm) and everything in between. The most common is around an inch overhang.
If you have a specific composite decking in mind, click here to read a fuller article about composite decking overhang. For this article’s sake, we will just assume an acceptable ¾” (18mm) overhang. Which is enough to cover most composite and PVC fascia board.
Like all things lumber, the “size” is not the actual size. 1×8 Trex fascia boards are actually 9/16” x 7 ¼” x 12 ft (14 mm x 184 mm x 365 cm). TimberTech is no different, don’t let the 1″ scare you. It’s actually thinner and will fit under a ¾” (18mm) overhang.
The actual dimensions of composite fascia board lean towards being installed under overhanging deck boards. As the 7 ¼” (184mm) matches the standard 2×8 rim joist. Yes, again, not the actual size.
Yes, you could pay for a larger fascia board, but that just creates waste. Which interesting matches the size of a 2×12 rim joist. Isn’t that interesting? I wonder if they are trying to tell us something.
A Royal White Pre-Finished Embossed PVC Trim Board which I have used for wood decks, provides a nice fascia finish at almost half the price. But it’s a little thicker than composite at ¾” (18mm), but with wood decking its tucks under easily enough with a 1 ½” (38mm) overhang.
Why is Overhanging Fascia Best Practise with Decking?
Glad you asked. There are two main reasons, appearance and protection. Decking overhanging the fascia will look better and will also last longer.
There are small differences in material thickness, which overhang will cover over, making it less noticeable. Or even with midspan joist blocking slightly pushing out the joist, which becomes really apparent without overhang.
But if the decking overhangs the fascia board, it all blends in. You won’t even see a ¼” (6mm) difference from a casual glance.
But if the fascia board sits proud of the decking, it’s noticeable. You will see that, and in time as dirt collects, you will see it even more.
Which lead us to our second point.
Decking Overhang Prevents Dirt Buildup Between the Fascia Board and Joist
That little sliver between the fascia board and joist collects dirt and water. Looking ugly and encouraging rot. Both not good.
But with the decking overhanging the fascia board, that little gap is covered over, protected from rain and dirt.
This is another reason you want the decking to cover the fascia board and overhang slightly past. Leading water just a little further away from the joist. It doesn’t seem like much, but it makes a difference.
Just like your nose leads water away from your mouth in the shower. The same happens with overhanging decking, “nosing” leads water away from the deck.
I have torn many decks apart in which boards are sandwiched together without overhanging decking. That’s where you find rot. Protect the fascia and joist, overhang the decking over the fascia board.
Deck Boards Overhanging Fascia Protects the Fascia Board
Not only does decking overhang protect the substructure but also the fascia itself. Composite fascia board is not designed to be walked on. The downward pressure can break the fascia board or tear it off the screws, which are only intended for hanging the fascia.
Remember your Mom yelling, “Stop hanging off the curtains. They are not designed to hold you”. Maybe that was just me, but the same is true with deck fascia screws. They are designed to hold the fascia, not a person.
But if the decking does not cover the fascia board, it’s doing exactly that. Every time you step off the deck, your pushing the fascia down and off the deck. I am not sure which is the better scenario, tearing the composite off the screws or breaking the board’s edge. Either way, it’s better to protect the fascia board by overhanging the deck boards. Decking is designed for walking on. Fascia is not.
How much Should Decking Overhang Fascia Boards?
Ideally, a ½” to ¾” (12-18mm), the more, the better. But with composite decking, this becomes hard. For example, Trex only allows ½” (12mm) perpendicular decking board overhang. Which doesn’t even cover the fascia board, which is 9/16″ (14mm).
I know I just said that fascia board is not designed to be walked on, but we will need to push the rules a little here. We will want the decking to overhang the finished deck that ½” (12mm). Providing that beautiful nosing around the deck.
So you are best to overhang the decking a full 1″ (25mm) past the rough rim joist. Then the fascia can be hidden entirely under the decking with the ½” (12mm) or so finish overhang. Providing a little play for slight variation.
This is why I always start my decking layout at the front of the deck. To provide for the required overhang of decking. If you start the layout at the edge of the house, the chances of having a consistent overhang once you get to the edge of the deck is low. Start with your desired overhang and finish with your odd ripped piece hidden under the flashing. Not the other way around.
Conclusion, Of Overhanging Fascia Board
Yes, the decking should overhang the fascia board. This will make for a better looking and longer-lasting deck. Ideally, the overhang will match the deck stair’s finished depth. Providing a consistent look all-around your deck.