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Question DetailsAsked on 5/28/2017

is it possible to lay plastic decking over a current wood deck?

Is it possible to lay plastic resin boards (Mfg name of product?) over/on top of the floor boards of the current deck boards? The deck is wood that I have now but hoping someone has tried this process with success. I've been told you can do this with linoleum tile or rolls internally for inside homes but can't imagine it wouldn't lift up eventually on the ends. However with the wood deck currently secured very well I am just trying to find out if this process has ever been done seems to me the long term maintenance would be substantially less and cost effective. Thank you. Your answers and guidance are appreciated.

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1 Answer


Indoors yes - it does not (hopefully) rain indoors.

Outdoors - sorry - I guess you might get away with it for some years with ground-contact rated decking, but in that case you would probalby not be wanting to overlay it unless it is very old - though you can retreat it yourself.

But the big problem with this is the overlay decking lets water through between the planks, which will then pool on the underlying planks and run in between the plastic and the top of the existing wood decking, leaving the wood saturated for long periods of time - an invitation to rot. I would expect your existing deck boards (and possilby tops of joists too) to start showing serious mildew and rot in about a year or less if untreated, maybe a few years if normal lightly treated wood, maybe 5-10 years if fully ground-contact 0.5 or 0.6 lb/cf pressure treated - give or take a bunch depending on local climate, etc. In Tucson or LA you might totally get away with it, in Maine or Mobile or Miami I would expect disasterous effects in short order.

One other consideration - unless you angled the new decking relative to the old, you might have some unsupported edges (at the old deck board gaps) and some warping due to uneven existing boards - and I am sure this would lead the synthetic board manufacturer to void your warranty, if you put any trust in that anyway.

If you are putting Trex or equal down at about $8-15/SF for the material alone and another say $4-8/SF for the installation, the probably around $2-4/SF (depending on local disposal costs) to remove the old decking is not that major a cost, to do the job right.

Note many manufacturers have a hidden interlocking tiedown system which uses metal clips or rails to fasten the decking, which holds it up a bit off the supporting wood - so in that case only the rails or clips would be contacting the existing deck, leaving at least a thin air space between it and the overlay - which should certainly help and make it more like the existing contact between current deck boards and joists - but would still have strips on the top of the old decking under the rails which could stay wetter, so while that is probably an improvement probably not an optimal solution. Plus if the connectors/rails are not stainless they would likely corrode a lot quicker than normal.

Bear in mind - if you are getting rid of the current decking then presumably it is well into its life so has maybe 2 to max 10 years before it becomes a fungal farm, and you presumably hope the new plastic/composite decking will last 20-30 years minimum - so what will you do when the old decking is rotting out - take up the plastic decking and the old wood, then put the plastic back down ? I think that is not the maintenance situation you are looking for - so I would take up the old now if it is past rehab or if you want to eliminate the restaining / recoating hassles.

Or go with my solution (subject to some if's if small kids will be crawling on it, because of the treated wood splinter issue - they fester up pretty badly, like cedar) - go with ground-contact rated treated wood and pressure wash with deck cleaners every few years as needed if you don't like the graying, and retreat it every 10-30 years as needed depending on your environment. (Mine is just over 30 years old and at the point where I will be thoroughly cleaning and pressure washing it and retreating it for the first time, in a moderate summer and severe winter climate).

Answered 3 years ago by LCD

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