Leaving a slight overhang is a common practice in deck building. Overhanging is letting the boards extend past the decking frame. Letting your deck overhang has both advantages and disadvantages. Many builders design wood decks to overhang, but can you do it on composite decking as well? What are the benefits and drawbacks of overhanging? And how much overhang should your deck have? 

Can Composite Decks Overhang?

Like any other deck, you can design composite decks to have an overhang. However, it should be a part of your deck planning and layout design. You can create overhang using several methods. For instance, after installing the decking boards, you may opt to leave a few inches off the boards. Another alternative is to set up picture framing, leaving a slight extension. In any case, you will need to include it in your decking plan design. 

How Much Can a Composite Deck Overhang

While it is a common practice in construction, many still wonder how much a deck can extend over the edge. The answer, however, is far from simple. Several factors determine how much you can overhang a deck. 

First of all, you will need to consult your local building regulations when it comes to overhangs. There may be a specific instruction or requirement depending on the area where you live. However, in some cases, there is no such specific regulation. What then? The rest is up to the manufacturers’ instructions or guidelines. The manufacturers may also test their products to see how much their boards can overhang. Some brands may use third-party inspectors for testing. Once testing is done, they can release information regarding their decking products. For instance, Trex recommends 102mm of maximum allowable overhang for their decking boards. 

When there are no clear instructions from the local building regulations or the boards’ manufacturers, there are other ways to determine maximum overhang. As a general rule of thumb, it should not exceed 1/3rd of the boards’ width. For decking boards, it ranges from 1/4″ to 1 3/4″ inch. If you plan to picture frame your deck, many recommend an inch of overhang. 

For composites, many consider 1 1/2″ as the ideal measurement. However, composites don’t have as much tensile strength as lumber. For this reason, many leave only 1 inch of overhang or flush the decking boards entirely. If you plan to install fascia boards, you can overhang the decking boards by 1 3/4 to 2 3/4 inches before attaching the fascia boards.

Benefits of Overhang

As mentioned, there are several benefits of overhanging your decking boards as opposed to flushing them. One of the main reasons why many extend their decks over the subframe is due to aesthetics. It drastically improves the appearance of your composite deck. It also slightly hides the outer joist of the deck. For elevated decks with stairs, overhangs also create a flawless transition between the stair nosing and the decking boards. 

Another crucial reason to overhang is to protect your substructure from moisture. If you have a wooden frame, water damage is one of the biggest concerns. Extending the decking boards past the edges help redirect water from rain, snow, or spillage away from your deck frame. In doing so, you can maintain your deck’s structural integrity, making it last longer. 

Disadvantages of Overhang

While there are several advantages of overhanging your decking boards, there are also a few disadvantages that you may need to consider. For instance, composite decking boards may leave unsightly and unappealing end cuts. Producing cleaner and smoother cuts on composites may prove difficult without the right tools. 

Another issue is that the cut ends of composites may be susceptible to several problems. While composites are water-resistant, these cut ends may not. The exposed ends can absorb moisture, causing the decking boards to warp or increase mould growth. Not only are the decking boards affected, but the frame as well. 

If you intend to overhang your decking boards, there are some ways you can do to bypass these disadvantages. For instance, you can use sealants and end caps to protect the cut ends. Not only will this hide the unsightly or rough edges, but it will also shield the boards from moisture. 

Should You Overhang Your Composite Decking?

You can overhang a composite deck, and it improves the deck’s appearance. Besides aesthetics, it can also help prevent moisture damage and protect the decking boards and the subframe. However, you will want to check in with your local building regulations and manufacturers’ manuals on instructions regarding overhang. In general, it should not exceed 1/3 of the width of the boards to ensure safety.