© 2008, rev. 2013 by Raymond Alexander Kukkee
Build a Freestanding Deck for All Occasions
Need a deck for entertaining and that big barbecue in the back yard? Planning a patio or deck? To build a deck is to add a new dimension to your home, one that includes utilization of the outdoors, has potential for entertainment value, and the self-satisfaction of putting some of those unused creative skills to work –all in one project.
A free-standing deck is not to be confused with a deck attached to the house by the use of ledger-boards, where support members or beams are attached directly to the wall or foundation of the house.
Don’t forget the building Permit and Restrictions
Some jurisdictions require building permits for decks, so be sure to apply for your building permit. Make yourself aware of any restrictions for height, size, and any specific structural requirements. Some jurisdictions, for example, do not allow attached decks, and they must be built specified distances from lot lines.
Why an ‘unattached’ or ‘freestanding’ Deck?
The back-fill around a foundation takes many years to settle, and uneven settling of the deck support structure is also possible. An attached deck may settle unevenly, causing structural damage. Other common problems include poor flashing of ledger-boards at the wall, with the inevitable result being water damage to the wall of the home. A support ledger may be fastened with suitably-sized Tapcon® screws, lag bolts or other concrete anchors to a cement wall if the foundation extends high enough, however in that design, moisture is inevitably trapped between the concrete and the ledger, resulting in decay if ledger boards and timbers are not isolated properly with essential flashing.
From a design viewpoint, a free-standing deck is a more versatile choice, allowing the homeowner to place it for optimum use and convenience. A beautifully-designed deck can also be a focal point for a future landscaping plan. Here’s how to build a free-standing deck.
Decide upon the size and location. Long-term planning for the space is critical and should be considered carefully. Outline the deck site with pickets and a ribbon or string, and carefully study the implications of building in that location. Take the time to make an informed decision and think ahead. Will it eventually be in the way of another project ? Will you need that space in the future for other purposes? Will you end up having to move it over, “just a foot or so” after it’s built? Does the placement suggest it will be used for spying on the neighbours? Is it too close to the lot line? Worth repeating, do you require a building permit? Careful planning in advance can prevent some serious headaches.
Choose the type of foundation you will use. There are several choices available, depending upon the height of the deck, the slope of the ground, and the intended use of the deck. Degree of difficulty varies. Foundation choices include:
• Deck blocks
• Post and beam
• Beam on footings
• Masonry posts
• Concrete foundations
For a simple, low deck on grade, choose deck blocks, specially formed blocks designed to support and carry a beam or short 4×4″ posts.
Establish the location of the blocks, dig out the organic material, and in soft conditions, excavate deeper, allowing a larger base of 6-8″ of crushed rock to be installed underneath the deck blocks for stability.
Install the deck blocks, leveling and lining them up appropriately using a line level, a clear plastic tube with water in it, or a transit level. Install the beams directly on the deck blocks, or install short posts as required, attaching the beams to the posts using suitable hardware, and frame the deck.
*Hint: Prior to framing the deck, take the time to install a ground fabric or black plastic underneath the deck to prevent the establishment of coarse weeds and other growth under the deck. Place a layer of coarse gravel, pebbles, or small rocks on the fabric to keep it in place.
Use P.T. (Pressure- treated ), dimensioned lumber suitable for exterior construction. Treated lumber will far outlast untreated lumber. Within a very short period of two years, most untreated lumber will begin deteriorating, begins to rot, and will soon be unsafe. Let’s do it right the first time, choose materials carefully and avoid the inconvenience and cost of rebuilding.
Ensure the span between the beams is suitable for the size of the dimensioned lumber chosen for framing joists, whether they are 2×6, 2×8, or 2×10. Do not over-span or cantilever the joist framing excessively; the deck will be “bouncy” and in the extreme can even collapse under excessive load. Use span recommendations from reputable building suppliers or building code sources. There are standard “tables” for allowable span and deflection of any specific dimensioned lumber. Remember, it is better to over-build than have a deck that is flimsy, bouncy, and weak.
Assemble the joist framing, squaring it exactly. Use the ratio 3:4:5 to square the corners, and finally, measure diagonally both ways across the deck from the corners to verify the deck is square. For a more attractive finished look and more solid construction, install joist headers to close in the end of the joists.
Cut deck material to length, enabling the alternating of joints, and for a superior modern, unblemished look, fasten the decking from the underside using proprietary fasteners. For individual planks or boards, always place the “cupped” side down, to ensure water drainage from the surface. Space individual deck boards 1/4″ apart, using a standard spacer for uniformity. Remember that most lumber will shrink to some degree.
Alternative fastening choices include fastening the decking through the top surface using galvanized nails, anodized “deck screws” or the equivalent in stainless steel. Drill holes close to the ends of the planks to avoid splitting. Always use anodized or stainless fasteners for deck applications. Ordinary fasteners will quickly rust, staining the decking.
Install the railing posts and rails to the correct height, which may be dictated and required by code. Rail height codes vary with jurisdiction. In some locations, any deck over 24″ above ground level must have appropriate railing. For safety, do take the time to find out what is required.
The installation of webbed skirting or solid alike is another choice that must be made. If you install solid skirting, ensure it is adequately vented to prevent moisture and subsequent decay of the structure. Skirting may be optional, but deck skirting serves several important functions:
- Aesthetically a deck with skirting is more attractive
- Serves to keep animals such as skunks and raccoons from establishing themselves comfy little nests under your deck
- Serves to prevent the natural collection of wind-blown trash from under the deck
- Discourages the parking of bicycles, gas cans, lawnmowers, water hoses, garden tools and other unsightly clutter from under the deck.
Finally, Install stairs, deck seats, and other accessories as desired. Stain the deck with a good quality stain as desired, and don’t forget the exterior wood sealant. Enjoy your beautiful new deck !
If alternative foundation choices are made other than deck blocks , the system most often used is ‘post and beam’, using simple concrete forms dug down to below frost level to install concrete posts for support. These pipe-like forms of spiral-wound, heavy cardboard fibre or paper construction vary in size, and are commonly from 6″ to 16″ and even much larger in diameter for other industrialized and specialized purposes. For a smaller, to average-sized deck, one might consider using 8″, 10″ or 12″ forms.
*Note: Although “Sonotube®” is a registered trade name, the popular generic, round, cylindrical concrete forms are erroneously called “sonotubes”.
To use Sonotubes© or the equivalent spiral-wound concrete forms, a suitably-sized hole is dug down to below frost level, and a layer of .l stones or coarse gravel is placed in the bottom of the hole for drainage. In very soft conditions, a layer of crushed rock may be installed, or a larger “foot” may be excavated at the bottom of the hole and concrete poured into it to provide additional footing. With either process, the form is then inserted, plumbed, and leveled. Support is provided by bracing or backfilling the outside with dirt or gravel. The form is carefully cut off at the level desired, usually 6″ to 12″ above the ground level.
*A cautionary note: “Call before you dig” is always a wise first step and can prevent unnecessary damage to gas lines, water lines, underground wires or other infrastructure.
The concrete form is filled with concrete and a steel “J-bolt” or specially-designed bolt assembly with a “U” structure attached is placed into the wet concrete, lined up and leveled accurately to enable it accept a 4×4″ wooden post or laminated beam after the concrete is set. The exposed portion of the cardboard form can be left on the concrete, or may removed at a later date.
Construction of the deck is typical, after installing posts to the correct height, bolting or fastening the beams appropriately using proprietary steel brackets, and the deck framing has been installed.
For very large decks, concrete footings can be poured, with beam pockets or auxiliary steel brackets installed. Masonry pillars of brick or stone may be subsequently built in place to the desired height to accommodate the beam and deck structure.
Regardless of the system you choose, working safely with care and effort, you can build a freestanding deck of which you can be proud. Get out the barbecue and think about a hot tub! By the way, if you planned well and followed these handy tips, you won’t have to move the new deck an inch to put in that new swimming pool .
Is that Incoming I hear?