There are approximately 40 million decks in the United States and only half of those are code compliant.
Every year we hear about decks that collapse under the weight of people or snow load. If you have an existing deck that is more than 3 years old you should have it inspected for safety issues and make necessary corrections by retrofitting safety hardware to make your deck safer and bring it more in line with code compliance.
Do You Need To Retrofit Your Deck? Or Replace it?
If your deck is 10-15 years old you’re at the end of that decks lifespan and should consider replacement or a serious rehab and retrofit.
Here are a few things to consider when looking at your deck:
Large cracks in framing should also be evaluated and replaced.
Missing or improper connections:
Toe-nailing or direct nailing of joists is no longer an acceptable way to secure joists with out an additional metal connectors added. Assuming you’re using the correct sized floor joists for your span, the addition of corrosion resistant or stainless steel joist hangers or hurricane ties is an easy way to make your deck flooring system stronger, safer and in compliance with International Building Code [IBC] and International Residential code. [IRC]
Follow the metal connector manufacturer’s recommendations for fastening any metal connector. My general rule of thumb is to use 16D galvanized nails everywhere I can.
Loose railings, stairs, ledgers or support posts:
Adding additional support to loose railings or ledgers can easily beaccomplished by using ¼” diameter Structural screws or thru-bolts to secure the deck from vertical loads. See VIDEO on Lateral Tension Device.
Thru-bolts should be a diameter of ½” installed through 17/32 to 9/16” pilot holes and have washers at the bolt head and the nut.
I like the structural screws because they do not require pre-drilling, are corrosion resistant and designed to be used with pressure treated lumber. Follow manufacturers’ recommendations for fastener length and placement.
Deck ledgers should also have a minimum of two galvanized or stainless steel lateral load connectors [tension ties] connecting the deck joist to the house floor system. [photo right] Each device should have an allowable stress design capacity of not less than 1,500 lbs.
I use Simpson’s tension tie # DTT2z on my deck in stalls and retrofits. These connectors tie the deck in to the hose and protect against lateral loads resulting from wind, seismic or people on the deck.
Loose deck support posts should be replaced and the deck frame should be checked to make sure it is still level and the footings have not sunk. Posts should be 4×4 or preferably larger and made from pressure treated material. Post to beam galvanized or stainless steel connecters should be used.
Inspect existing joist hangers, connectors and fasteners for corrosion:
Fasteners and connectors can corrode over time. Inspect your deck fasteners and connectors for this as well to see if the proper fasteners were used. For example, many ties people will install joist hangers but then use improper nails to install them. People often install the wrong size joist hanger.
Joist hangers must meet IBC and IRC code of downward capacity. You can determine this by usin g an approved manufacturer’s product data based on the dimensions of your joist or header that you are carrying.
Use the recommended nails and fasteners for the metal connector you’re installing. Roofing, screws and box nails have no place in any metal connector fastening system and should be replaced and avoided at all costs.
Also make sure to install a properly sized nail or fastener into every metal connector hole provided.
Deck support posts should be mechanically fastened both to the footing in the ground and the deck frame or beam. You want to ensure that your deck support posts resist lateral and up lift movement.
If your posts are notched to hold a beam they should be a minimum of 6×6 [nominal] and have a corrosion resistant post to footing and post to beam connector. There are a few retrofit options available to accomplish the post to beam. These connections are needed to resist lateral ad uplift loads.
Replacing the post usually means temporarily supporting the deck and then adding proper metal base connectors. For retrofitting a metal connector into a proper footing you can drill a hole and use a mechanical wedge anchor or epoxy an anchor in place.
Adding diagonal bracing to both the parallel and perpendicular side of the deck post is also a good ideal to reduce lateral motion and racking of the deck. Diagonal braces should be installed at a 45 degree angle 24” down from th e beam and 24” out from the post.
Deck posts should rest on and be anchored to concrete piers. Footing size are dependent on factors such as live and dead loads and ground conditions.
Concrete footings should be at least 12″ below the undisturbed ground surface and in my neck of the woods, below the frost line to prevent heaving. Follow your areas recommended footing depth to meet local code.
Guard Rails and Railings:
Railings are a critical safety connections and should get a thorough inspection for safety.
Railing posts must be attached to the decks rim joist and tied into the deck joist framing. Use two through bolts on your post and use a Simpson’s tension tie # DTT2z or a HD2A hold down for the top bolt connection.
Guard railing posts should be a minimum 4×4 size and be attached to the outside joist and rim joist of the deck. They can be retrofitted with a tension tie, through bolts and or blocking as needed. Follow IRC code requirements when installing fasteners into guard posts.
If guard posts anchoring does not have a minimum allowable tension load of 1,800 lbs for a 36” maximum railing height they should be replaced. The same tension ties used too tie the deck joist to the house can be used on railing posts and attached to the top bolt installed in a post.
If your deck is more than 30″ off the ground it requires railings and guardrails. Depending on the application guard rails can be either 36″ or 42″ – refer to your local code.
Stairs, stair stringers and stair guards must meet the IRC design and strength requirements height and opening /spacing requirements.
When checking the steps you should have a consistent step with a 7-3/4” maximum height riser. A 3/8” deviation from one another is allowed by code but should be avoided.
The tread width should be a 10” or greater.
Inspect the stair stringers, posts and railings for cracks, rot and solid connections. Additional metal connectors can be used to connect stair stringers to the deck frame as well as support legs with footings can be added under stringers. The best advice to stairs is if they are starting to get wobbly or show excessive rot – replace them.
A Safe Deck
Improperly built decks can be dangerous. Local codes were created to keep us safe. Have a qualified contractor look at your deck and evaluate it for retrofitting if applicable.
By retrofitting your existing deck you can ensure a continuous load path and feel assured that key connections are being made on the framing system and the deck is safer and code compliant.
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