Heritage Restoration, Inc.

Choosing the Right Decking

What type of wood is best for decking?  Karen, East Greenwich


The Best Types of Wood Decking

Decking seams or joints that hold water longer after rain events are more prone to decay than joint designs that allow for quicker drying.  So be sure you properly space decking, about an 1/8” apart or a thick nail, so each board can dry.  I tend to stay away from tongue and groove floors, unless they are covered, because they grooves will stay wet and rot.  You can pretreat tongue and groove, just be sure the wood acclimates to the conditions before installation.


If the wood fibers stay below a saturation point of around 20% or so, fungi can remain dormant, preventing decay of the wood.  That is why wood with ground contact should be either very resistant to decay, like heartwoods such as white oak, old growth redwood or locust, or treated woods using natural or toxic chemicals.


Naturally Resistant or Very Resistant to Decay

Garapa (Apuleia leiocarpa), also known as Brazilian Oak, is a South American hardwood.  It is considered very resistant.  It Garapa is a golden to yellowish brown color, which darkens with age. The wood changes luster or color and appears to shift from dark to light coloring in different lighting angles. It resists rot, decay, splinters and fire naturally without any chemical treatments.


Ipe (Tabebuia alba) is a Brazilian hardwood, by 2007, FSC certified ipe wood had become readily available on the market, although certificates are occasionally forged.  Ipe is extremely dense, dark in color, resists warping, and wears very well.  It must be pre-drilled and screwed with stainless steel fasteners, not nails.  Ipe is very resistant to decay.


Dark Red Meranti, also called tanguile & dark red seraya, is not a mahogany but from the Shorea genus.  It typically comes from the Philippines.  Do not be fooled, there are many Meranti’s out there.  The Dark Red Meranti is the best, while the light red, yellow and white Merantis are slightly or nonresistant to decay, meaning they will rot as quickly as pine.


Cedars can be a domestic wood, although there are many varieties.  Cedar trees will usually grow to a height of up to fifty feet, but others can reach one hundred or more feet in height.  As a rule only get heartwood cedar, since the sapwood is not decay resistant at all.  The best decking choices are Western Red Cedar (softer and can scar easy) and Alaskan Yellow Cedar (a bit denser).


Moderate to Low Resistance to Decay

The trouble with using other woods such as fir and pine is they likelihood the stock you get will contain sapwood, which will rot in a few years.  Heartwood Douglas fir used to be terrific decking, with growth rings as high a 20-25 rings per inch, as opposed to today’s varieties at about 6-10.  I have actually reused 100-year-old fir for my deck, and with proper care, it still looks great.  Other woods such as southern pine (Pirrus spp.) and white spruce (Picea glauca) have lower decay resistance than Douglas fir heartwood.


Treated Woods

The trouble with many treated woods is that the wood itself is not very resistant to decay, just the chemicals are.  Woods like spruce and Douglas fir are farm raised at an accelerated rate, where the growth rings can be as little a 2-3 per inch.  So when the chemical fades, the wood rots.  Also, these wood come with a very high moisture content, causing the wood to split, crack and warp within the first few years.  The grain is also not vertical, so the wood fibers will lift and cause splinters if not maintained with a good preservative.  Specific fasteners must be used with treated woods, or they will stain the wood and the fasteners will rot.


Chromated Copper Arsenate (CCA) is a highly toxic treatment that was discontinued in 2003, although is still used in some non-residential applications.  Ammoniacal Copper Quaternary (ACQ) and Copper Azole (C-A) act as biocides to prevent insects and fungi from attacking wood.



If you are putting down a wood deck very resistant to decay, always use stainless steel with common head screws.  You can use 2 stainless steel face screws predrilled per joist, or an appropriate stainless blind fastening system.  Always pre-drill.  Finish nails, ring shank nails, and trim head screws will pull when the wood eventually moves.


Blind fastening systems work very well.  There are many types.  Some have teeth that hammer into the side of the wood, which can work well for softer woods.  Others require a saw kerf to be cut into the side of the wood, which are better for more dense woods.  The type of metal and finish depend on the wood you will use.



All wood requires treatment using designed formulas for the density of the wood.  Most applications are required after the first year; some require it every year, while others can go longer.  Look at the manufacturer’s directions for proper coating techniques and intervals.




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