Local codes were created to keep us safe, and many existing decks do not meet current safety codes. This often is determined by the joist span needed. Joists. I asked my local building official how he checks a deck plan to make sure the joist size and spacing combination will meet the code. He replied. Design for. Code Acceptance recommended meet or exceed minimum requirements of the IRC. Provisions . The span of a joist is measured from the centerline of bearing .. capacity of less than 1, psf are likely to be present at the site.
He replied he goes to the 40 lb. The problem is that those tables are intended for interior floors, not decks. Decks get wet and may be framed with incised treated lumber so span reductions need to be applied.
The table includes spans for common lumber species used for deck framing like southern pine, Douglas fir, hem-fir, redwood, western cedar and others. The table accounts for wet service conditions and an incised lumber reduction for species commonly incised for pressure treatment penetration.
The table has two column sections — one for joists without a cantilever and one for joists with a cantilever. The illustrations one for cantilever joists and one for flush rim-beam hung joists point out where joist span measurements are taken from — the saddle of the ledger mounted joist hanger to the center of a dropped beam or saddle of the hanger on a flush beam. Deck Cantilevers Section R The next subsection requires that solid blocking is required over the beam when there is a cantilever.
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So run the table by your building official for approval before using it. My general rule is to use 16d galvanized nails everywhere I can. Rim Joists Once the ledger is attached to the house we install a rim joist on either side and one rim or beam opposite the ledger. Once this frame is built we take diagonal measurements and use the method to square the frame. We dig concrete footings to support all deck posts.
The wider base also helps prevent frost heave from lifting the deck. The depth of the deck footings will be determined by your local frost line and building codes. Deck posts are supposed to rest securely and centered on these footings with a threaded anchor or J-bolt holding it down.
Anchor bolts are designed to resist post movement and deck uplift from high winds. Tube-shaped cardboard forms can be cut to length and placed in the holes to pour the concrete footings. Most deck footings these days are either poured in place or precast.
When poured in place most folks use footing forms from Bigfoot Systems, Sonotube or an equivalent concrete form. These tube-shaped forms are simple to use, easy to install, resist settling, and prevent uplift caused by frost to result in a stronger deck foundation.
Deck support posts should be mechanically fastened both to the footing in the ground and the deck frame or beam. Metal brackets make a strong connection while raising the wood post away from standing water.
The frost line depth is not consistent around the nation because there is such a dramatic difference in climate from state to state. The frost line in southern Florida is less than a foot, while in northern Minnesota it approaches 6 feet.
The average frost line in Massachusetts is between 30 and 35 inches. My inspector wants to see deck footings 48 inches deep. The best source of information regarding your frost-line depth is your local building department. Footing Diameter The diameter of the holes for your footings especially large ones, create significant concentrated loads within the soil. If you calculate the weight of the entire deck, the furniture placed on it and the combined weight of a large group of people who might be standing on it, you will be shocked at the number.
Even a small deck might weigh in at 10, or more pounds. Use metal joist hangers to connect all joist ends. If your deck has wood support posts and a ledger board that is bolted to the house, the deck posts holds up approximately 50 percent of the total weight.
In this situation, the soil under each deck footing may be called upon to support 3, plus pounds. Small sections of joist material can be installed between the joists as mid-span blocking to help prevent deck bounce and strengthen through-the-deck rail post attachments.
Depending on the porch load, the diameter of the hole will probably range between 8 and 24 inches. Larger diameter footings spread the weight out over more soil area. Footing tubes come in different lengths from 4 to 10 feet. The tubes are cardboard and are easy to cut with a hand saw. Fill them with concrete, using a shovel to work out air pockets.
Apply the J-bolt and allow the concrete to cure for one week. Once the footing is cured we install support posts. Depending on where we are on the project, I might install the joists before pouring the footing or vice versa.
Either way, the temporary supports will hold the deck in place until we install and connect the deck posts to the footings. Support Posts 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 uplift movement.
How Far Can a Deck Joist Span? - Fine Homebuilding
Decks can be built with all sorts of designs. This small area was designed to store a gas grill. There are a few retrofit options available to accomplish the post to beam. These connections are needed to resist lateral and uplift loads.
Adding diagonal bracing to both the parallel and perpendicular side of the deck post is also a good idea to reduce lateral motion and racking of the deck.
Diagonal braces should be installed at a degree angles 24 in. We start left to right and mark out the ledger and outside rim joist inches on center in a square line. We cut all our joists at the same time, toe-nail them to the ledger and direct-nail them through our single outside rim joist.
Building a Code-Compliant Deck - Extreme How To
Toe-nailing or direct nailing of joists is no longer an acceptable way to secure joists without additional support, so we add metal joist hangers afterward. If the joist has a crown—a slight arc along its edge—install it crown-side up.
Roofing nails, screws and box nails have no place in any metal connector system and should be avoided and replaced at all costs. Also, make sure to install a properly sized nail or fastener into every metal connector hole provided.
Since we did not design a beam in this deck, the outside rim joist is then tripled, and is supported by the deck posts. Mid-Span Support Mid-span blocking can be used for a variety of purposes in deck building.
Probably the most commonly used technique is to install small pieces of material in between the joists to help prevent deck bounce and also to increases the strength of the rail post attachment.
Often times scrap materials from your framing lumber may be used for blocking; we often use joist cut-offs. We snap a chalk lines across the joists to lay out blocking. Install blocking in each joist bay, alternating the block along the chalk line to allow direct nailing. Install the blocking flush with the top of the deck frame. Flashing and Trim We install a metal or PVC flashing cap over the ledger board using roofing nails, and only place fasteners high up on the flashing. We also like to install protective flashing to the joist tops.
We accomplish this by using tar paper and staples on the joist tops, or a rubber membrane. We then install all of our perimeter trim on the rim boards prior to applying decking. Decking A deck should complement its environment, your landscape, and enhance your outdoor living space. Your deck, therefore, should ideally complement you and your lifestyle. Whatever your reason for building a deck—for entertaining, relaxing or outdoor living, you will need to consider materials for your decking.
Granite steps provide access to the finished deck. On some of our decks we use composite deck boards. Composite decking has the beauty of wood without the concerns of splintering, rotting, maintenance or weather damage.
Composite decking is simple to maintain and offers superior stain, fade, scratch and mold resistance. The decking surface is also easier to clean, which equates to less maintenance. Some brands come with matching, colored plugs to conceal fasteners. Once installed the plugs almost disappear. Also available are colored screws to match the decking, as well as various hidden-fastener systems that are concealed beneath the deck boards.
The posts of the railing system should be connected to the rim and joists or blocking using through-bolts and metal tension ties, such as the Advanced Lateral Anchor System available from DeckLok www.
We let the end of the decking run long, off the deck, and cut it later with a track saw.
This is faster than trying to measure each board and get the ends to match up. If you built your deck smaller than the longest available decking board length, you can install the decking without any joints. We use our speed squares to space the deck boards from each other during installation.
This provides even, consistent and professional looking deck-board spacing.