For a one level rectangular raised Trex deck attached to a structure.
0) PERMITS: Ensure all needed permits are obtained and in hand.
1) LOGISTICS: Find the location of the project and determine the logistics of the area. Is there sufficient work space and access? Where are you going to store the lumber and your tools? Where are you going to cut and prepare the lumber? When is trash day? When do the gardeners come? Etc. Move any furniture or potted plants out of the working area so that it can be easily cleaned as needed.
a. Determine the finish elevation of the deck. If there are any questions or options, get this sorted out right away.
b. Check the level, if it is along a patio or walkway that is slightly sloped, decide how best to handle this, if the whole deck should be slightly sloped keeping it flush to that level, or if there is to be a step up that will be higher on one end than the other.
c. Check the elevation of any significant features, like steps, retaining walls, etc.
d. Determine the physical area of the deck and ensure there are no problems with trees or other features that may interfere with the construction. First figure out what is there, then determine how you are going to handle it. Take up any problems with anyone else involved, once you have figured the best solution.
a. Make a working sketch with a plan view, preferably to scale showing the structure all joists and beams. Determine the sizes of the lumber from local building codes.
b. Also draw a cross section of the structure, not to scale, including any steps or levels.
5) MATERIALS: Make a materials list to ensure sufficient amounts and lengths of the needed lumber. Order the materials that are to be delivered. Pick up others as needed and deliver to the job site.
7) DEMOLITION: Do any demolition needed of any old structures or any plants that need to be cut back, taken out or relocated.
8) FOOTINGS: Check the condition of the existing footings or the placement of the new footings. Re-furbish the existing footings but drilling in rebar dowels and capping with new concrete and bracket around the old footing. If new, dig and pour new footings ensuring they are well above the existing grade. If there needs to be a grade beam, which is a foundation used to attach the deck to a hillside, do this in conjunction with the footings. NOTE: If it is permitted, once the holes are dug, call for a footing inspection and show the inspector the holes and metal before you pour the concrete. There may be additional concrete work needed if engineered.
9) LEDGER BOARD: A ledger board is a board attaching a new structure to an existing structure. It is installed 3/4" - 1 ½” below the finish elevation of a deck, which depends upon the size of the decking you will be using. The top of this is called the structure elevation. From this elevation shoot a level with a laser level to each footing to determine the length of each post at each footing, which would be that length minus the width of the beam and joist (for a laser level also minus the usually ¾” that the laser beam is above the structural elevation). NOTE: The ledger board is usually attached to an existing structure with 3/8” x 6”lag bolts 16” on center (o. c.) into each stud, or ½” x 7” Tru-bolts 16” o. c. into a masonry wall or foundation. The board is always pressure treated and usually water-sealed with ASPHALT EMULSION (Henry’s 107 water-sealer). Spacers between the concrete and ledger board allows for drainage and aeration.
10) LUMBER DELIVERY: When the lumber is delivered, ensure everything is there, or work out any problems. Move the lumber from the street sorting it as you go so that the pieces are available in the order that they are available. Large lumber may be cut to approximate size for ease of moving. A hand truck is used to move large beams, and they should be evaluated as to which side is the top by looking down it to see which way it is bent, or which side has a tendency to warp. It should be placed so that gravity and the weight of the deck would tend to straighten it out, making it “pre-stressed”. This top should be clearly labeled “TOP”. On the top should also be labeled where the middle of the board is with an “M” so it is known where the center of gravity is for purposes of balancing it. The lumber should be moved back as soon as possible for safety and so as to minimize the inconvenience. The Lumber should be laid out so that it can dry as much as possible in the sun, especially if it is to be stained, and it should also be easily covered with a tarp in case of rain. Once the rain has stopped the tarp should be removed as soon as possible.
11) POSTS: Posts are the primary vertical structural component holding the structure at the desired elevation.
a. Cut each post, treat the ends with JASCO TERMIN-8 or similar wood preservative. (NOTE: all cuts in pressure treated lumber and all butted ends of any large lumber are treated with Jasco Termin-8, which is a highly toxic wood preservative, and we referred to it as “the nasty stuff”) and/or asphalt emulsion – usually both on the bottom.
b. Stain the post if it is required, before installation.
c. To install, set the post in the metal bracket and with it fairly well leveled up, draw where the holes are to be drilled. Take the post out and drill all the holes half way from both sides, including the holes needed for the beam attachment, which can be put on and then install the post with the bolts and level it up. The holes should be 1/8" larger than the diameter of the bolts being used.
d. Do this with all the posts and then look across the tops of them to ensure there is a straight line for the beams to sit on. Make any corrections needed by re-cutting or fit a treated block on the top so that it is straight or very slightly crowned.
12) BEAMS: Beams are the main horizontal structural component carrying the weight of everything above it. There may be several rows of beams on a large deck.
a. Cut the beams to fit with the posts level, cutting any end corbels (detail end cut) as needed, sealing the butt ends with a heavy duty wood preservative and stain the rest if needed before installation.
b. Install the beam with the arched side up, which should be noted as “TOP” from step 11, and is referred to as pre-stressing. Install by the stepped brace method, by a “High Lift” device or if it is not very far, just lifting it into place. On a slope, a joist board can be nailed to the post and the beam slid into place. Shoot it in place temporarily with a nail gun, and then firm them up with bolts or connectors.
c. When the beam is in place, put a strap across any splices, caulk the connections on the top and sides, but not the bottom and you can apply asphalt emulsion, roofing paper or flashing to the top of the beam for moisture protection.
13) CROSS-BRACING: Cross bracing is needed for lateral stability – primarily in the event of an earthquake or other catastrophic event. It can be accomplished by bolting joist lumber at a 45 degree angle from the post to the beam or by knee braces bolted on underneath the beam to the post. The KNEE BRACE is usually post material, 4x4 or 6x6 lumber and cut at a 45 degree angle on each end and is used for lateral stability, and can be custom cut to produce an aesthetic effect. They are bolted on the bottom though the post with “through bolts” and lagged into the beam at the top. The picture below shows a lag bolt, which isn't as good.
14) JOISTS: Joists are the top structural level of the deck and are what the decking is attached to. They are perpendicular to the decking and on top of and perpendicular to the beams. NOTE: Each layer of the structure is perpendicular to the last.
a. JOIST HANGERS are metal brackets usually used to attach the joists to the ledger board at 16” o. c. (on center) and are shot on with joist hanger nails by an air palm nailer, always using safety glasses. NOTE: If the Trex decking is to be installed at a 45 degree angle, the joists would need to be spaced 12” on center. The joist hangers are best installed by setting the joist in place and nailing them in, or by using a small section of the joist board resting inside the joist hanger so the exact placement can be perceived and then nailed.
b. The joists are selected to be pre-stressed so that they are installed with the arched side is up and fit into the joist hanger so that the top is flush to the ledger board. If it isn’t flush, shim it up with a wedge or scrap piece of pressure treated board, or notch the bottom if too high and then nail into place. The end joist should be exactly 90 degrees square by checking with a framing square or a laser square and nailed to the beam.
c. Space the joists along the beam with the same spacing as the ledger board and toe-nail (nail at an angle from the side of the board) into the beam with two nails on each side or with L brackets or hurricane clips, Simpson H1 or H2.5. Square up the last joist - the square-ness of the deck can be cross checked by measuring the distance between the two opposite corners, which should be equal.
d. Cut off the ends of the joists by first measuring the same length on both end joists, snapping a chalk line and drawing a square cut line with a speed square, cutting with a skill saw and treating the cut ends with a heavy duty wood preservative.
e. Nail on end joist or fascia board ensuring corners are square. If the edge of the deck is too high to hold the fascia in place, a block can be screwed to the bottom of one of the middle joists to balance it until the first nails are in. If the joists are twisted, you can notch a 2x6 with a 1 1/2" notch and use it as a wrench to pull the joist straight.
15) RAILING POSTS: If there is to be a railing of 4x4 posts, the span between the posts should usually be less than 6 feet for a wood railing or 8’ for metal rails between wood posts. The spacing of the posts should be approximately evenly spaced, but it is structurally best if the post is next to a joist. If it is close, put the posts next to the joist and along the fascia board with three ½” x 6” carriage bolts total, two in the fascia and one in the joist. If it comes out so some of the posts have to be in the middle of two joists, cut a block approximately 14 ½” long and sandwich the post between the block and fascia board. Level the post and nail in the block and attach the post between them with two ½” x 7” carriage bolts. Note: A carriage bolt in wood always needs a washer on the nut, unless it is going into a metal connector.
16) APPLY TAPE (one of my secrets): This leaves a water tight gasket so that the joist is protected from water damage where it is most vulnerable. Joists tend to rot out where the screws or nails penetrate the wood. This step alone adds probably ten years of life to the deck. Install 10 mill PVC (poly-vinyl chloride) tape (pipe wrap tape) to the top of all joists, ledger, fascia and any blocking around the posts that the decking will be attached. Do this in a without stretching the tape or it will pull itself off, especially in the heat. This is best done by pulling some tape off the roll, sticking it down with the tape loose, then holding the side towards the roll and pulling it off the roll, letting it go slack and smoothing it down in its relaxed position, then again holding the end and pulling it off the roll, etc. The ends are cut with a utility knife. A staple or roofing nail on each end helps to hold it in place from shrinkage in the sun or foot traffic while working.
17) TREX DECKING is a composite material made of sawdust and recycled plastic.
a. Install decking by starting on the outside edge, notch the first piece around the posts leaving about ½” overhang on the front edge. Screw in two 3” stainless steel finish screws into each joist ensuring the board is straight by sighting down it from the side of the deck. The head of the screws should go into the Trex about 1/8” so it can later be pounded to give the “screw-less” appearance. There should be a 1/8” gap or so between the butts where the Trex is lapped so it won’t buckle in the heat when it expands. The exact rule is the gap should be 1/16 of an inch for each 20 degrees below the hottest temperature for a twenty foot board. Therefore, on a very hot day, there doesn’t have to be much of a gap at all as it will only shrink when it cools, and if it is a colder time of the year the gapping needs to be wider, as it will expand when it gets hot. The ends should overhang at least 1” with the final cut to be made later. If one side butts up to a wall, there should be a ¼” gap for expansion.
b. The next row of Trex should be evenly gapped with a wood chisel to between 1/8” to 1/4”. Any but joints in the decking should be staggered and in some regular pattern. The piece may need to be straightened by screwing it in on the ends and prying it out in the middle and then screwing it all in. If the piece is bent the other way it can be screwed on one end and the middle and then pry out on the other end and then screwing it all in. Every few boards, sight down the spacing to ensure it is going down straight. Make slight corrections as you go to insure the decking looks nice and straight. It works well to go along for about four boards just connecting them in three or four places, coming back filling in all the screws and then pounding them flush. The pounding can be a later step and is best done by first pinching the mushroomed Trex sawdust together before pounding it with a couple of wraps with a flat faced 1-3 lb. hammer.
c. Continue screwing down the rows of Trex notching around any other posts. The last row will likely need to be ripped for a flush fit, it will be the same size on both ends if your spacing is good, but check the distance to the end several rows back and if possible, adjust the spacing a bit to come out even at the end.
d. For the end cut, with a chalk line make a line 1” from each side and cut the ends, preferably with one cut with a skill saw, which won’t usually quite make it to the end, so the last few rows should actually be cut to actual size with the 1” overhang.
18) RAILING: The railing can be easily installed using 8’ metal railing sections between the posts. These sections and their attachments are available at Home Depot. Use only The best grade of metal fencing guaranteed for ten years, called category C. Just cut the sections with a carbondium blade to fit minus enough room for the connectors, spray paint the cut ends and screw to the posts with a 4” spacer under both ends to hold it at the same height until screwed in. It looks good to make post caps of a square piece of 2x6 with rounded edges.
19) SKIRT: A skirt is a façade built to hide or seal off the underside of the deck for fire resistance. It is an option that may be required. It is usually constructed by using the posts and beam for the sides and top and fitting STRINGERS, which are a structural element used to support something, between the posts a few inches from the soil. Either stained fencing boards are fitted and nailed on, or lattice panels are formed into this structure. NOTE: If the deck is in a high fire zone, they may require a skirt made of 2x lumber or stucco.
20) CLEAN-UP: The area should be totally cleaned up, hosed down, all refuse removed and any messes or mistakes corrected.
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