Materials and Fixings for Garden Decking
In any building project certain factors need to be considered which will affect the look, feel and lifetime of the finished project. The most important one inis the timber that you decide to use. There are five factors that require consideration when choosing timber: availability, appearance, life expectancy, structural strength and cost.
With the wide variety of timbers you can now purchase it is often difficult to find which wood is best for each application. The majority of timber used in deck building is such as pine. is available but the price is often a deciding factor and the finish is not that much better; its resilience to decay is not such a major factor now that timber preservatives are so good.
from colder climates is the best as the growth rings are closer together and give a stronger board, less prone to warping. Some of the most popular woods include Western Redwood (Sequoia), which is very resistant to decay and need not be treated prior to use; Cedar (Thuja plicata), which is noted for its light weight, great strength and durability; and Red Pine (Pinus resinosa), a timber often sold as Redwood but not quite as robust, though the price tips the balance in its favour.
Always buy tanalized wood if you are using softwood as it is a far better way of resisting decay than trying to paint on a preservative.
When looking for a timber supplier for your deck check to see if they offer a guaranteed life to the timber, often of 15 years or more. If no guarantee is provided move on to another supplier.
The finish on deck boards can be one of many styles. Some have all the sides plained smooth, often available on the best and more expensive types. Others have only one face plained — this reduces the cost and is ideal for those building a deck on a tight budget.
Thru Bolts (Rawl Bolts)
Rawl bolts are used to fix the first joist orto masonry walls. They need to be spaced every 60cm along the ledger to support the weight of the deck and people.
Coach bolts are used for joining joists to posts and provide a very strong fixing. Use stainless steel as any corrosion will stain the wood. The length required is the thickness of the two timbers plus 25mm to allow for a washer and nut. Ideally use size M10 or M12.
As coach bolts except theyin with a spanner. Very secure fixing which is good for larger timber where the use of an electric drill may be dangerous, ie near water.
Deck Frame Screws
(Posidriv) The main fixings for the frame will be 6 x 80. Secure fixing and easy to undo. Posidriv are best as they are less prone to slipping when using a power driver.
(Posidriv/Square Socket) The deck boards use 5 x 50 screws that are self-drilling and self-counter-sinking, making the need for pre-drilling unnecessary Again they must be corrosion resistant.
Deckare not as good as screws or as secure, but are ideal for inserting because appearance is not important. It is essential to use galvanized nails.
Grooved or Not?
Depending on the look you require, grooved board has a number of benefits over smooth board. For one thing, it is better for steps as the grooves do not become as slippery and channel the water off the decking. Grooved deck boards can also be used to show a change in height or a step by laying them in a different pattern to draw your attention to the change and make the step more obvious.
Fixing the timber is best done with screws as they have obvious advantages over nails. The most important is the ‘draw strength’ — the amount of energy needed to pull aout of the wood is much greater than a nail would require, therefore creating a far stronger joint. Screw joints can be undone easily and moved if required and it is much easier to remove decking boards if you have screwed them down rather than nailed them. Screws will also stop the deck boards splitting when fixing them.
The screws must be corrosion-resistant otherwise they will rust and break over time.
When joining larger joists and posts together, it is essential to use coach bolts as large loads will be transferred to the posts through this fixing.
Your final choice will be how far your budget will stretch to — if you can only budget to pine rather than redwood, then so be it. You will still have a deck that, with the correct treatment, should last 15 years or more.