Plywood life expectancy ?

[Steve Kennedy]

I'm seeing a lot of really neat plans for hope/ blanket chests using plywood. My concern is how long will the last !!  I "hope" to make each of my 3 granddaughters their own but I'd really like their granddaughters to still be using them a hundred years (or 100's) from now !! Any suggestions ? Thanks

[rich b.]

Hi Steve, if you use good quality plywood and it is sealed on both sides it should last a very long time.moisture and abuse would definetly shorten the life.Most of my projects are done in plywood for the larger areas and the ends are capped just like kitchen cabinets.By sealing both sides,top and bottom and the underside it will help prevent moisture and warping.

[Jeff Metcalf]

Hi Steve;

Rich is correct on what he said about plywood, there is several different types and grades of plywood with different adhesives and laminates of different thicknesses. Most of us will use a cabinet grade plywood you can get marine grade, I use to buy a special plywood for signs that had a wax paper laminated on it for outdoor signs.

My memory must be going I can not remember the name of that plywood, the fact is plywood will be more stable and if it sealed properly like rich says you should be fine. if you can find a speciality wood supplier you can find the right plywood for the job.

Good Luck Jeff

[Jay Boutwell]

Steve, adding to the well stated statements of Rich and Jeff, I might add that the quality of Plywood had fallen drastically in the last few years.  If you buy your plywood from a discount store, and sorry to say, this includes Home depot and Lowes and  other big box stores, you will get a plywood that is inferior to that of what you buy at a cabinet supply or hardwood supply outlet.   The cost is a bit higher but the quality of the plywood is much better.

Some of the things you will encounter in the cheap grade plywood will be voids in the sheets, lumpy surfaces that will show in the finish when you apply it.  The lumpy surface is due to loose pressed plies that appear from bad lamination of the glued plies in the structure of the plywood.  These become lose after the plywood sheet goes through the press and rollers.   Some times it is due to soft wood of which the press rollers leave indentaions in the soft surface and then  pass over the harder woods. Most times, if not always, you will get a finished surface that is lumpy showing inpressions of the press rollers and the veneer will be so thin that sanding will not cure the ailment.  Agressive sanding will go through the veneer.  Of course you may not notice this until your project is finished and you stand back to admire your work and get the shock of reality.   I have seen several example of this when you go to any cabinet outlet and even furniture where you will see surface defects in the form of delaminations, lumpy surfaces and even rotary marks from surface sanding and or machining.  Most of the shinny furniture and or cabinets are either made of solid woods or plastic which is another chapter in cabinet and furniture building industry. 

 In the cheap grades you will get delaminated plies that come apart when you add a pocket screw or other fasteners to the ends of the plywood.

  I have seen several comments in the community about the plywood being thinner than 3/4 inch.  I never worry about this as it does not change anything unless you are cutting dado's for construction and then just cut the dados to fit the plywood thichness.  I worry about the voids and delaminations and surface with the thin veneers.   This is what will determine the life time of your project.   This thinner than 3/4 inch plywood came about not only as a material saving issue but most of the plywood is imported and in Europe everthing is made around the metric system.  The only real 3/4 ich thick plywood comes from the US plywood mills of which have mostly closed down now.  I tmay be years before this changes again so you have to adapt to it.  The tool Industry has made adaptation to this and has tooled up and made router bits that are undersizes to cure this problem several years ago.

The experience that I have had over the years tell me not to use the cheap plywood but to use the cabinet grade materials.  Even then you will often encounter the thin veneered surface that is lumpy and shows after you apply your finish.  Because of this alone, I changed my method of building cabinets over 15 years ago and now add a 3/4 inch thick panel on all surfaces that the eye will see after it is finished. The panels will be made of solid wood of which you can sand out to a very smooth surface. This is a insurance against the possible defects in the appearance of plywood.  This way I know that I will not have a veneer coming off on a panel or the possible unsatisfactory look of a cabinet with a plywood face that will be large sore on your project.

To day when picking your materials you must be careful of the quality and select the best that you can.  It takes time and is a big part in the overall outcome of your project.  It is a must to learn how to select and purchase of your materials.  Learning how to do this is a major part of building anything and in the end will make you a better woodworker.  I never consult with the lumber broker but will make my own choice based on a good solid knowledge of wood charteristics.

  In my custom furniture building and or things like hutches, dressers, chests and things of that nature, I perfer to build only with glued up solid wood that I glue up from my own milled lumber.  About the only thing that I use plywood in furniture is drawer boxes,shelves that are on the interior, cabinet backs and for cross members and braces.  Sure it is more costly but on the good side of this you have a quality piece when you finish.  It might cost a bit more but that cost is well worth it in quality and is good insurance for you know that there will be no delaminations later and or a bad looking finished surface.  The problem with plywood surfaces that you see you often will not see the bad surface until you apply the finish.  I have seen them where the surface is smooth as glass but when looking at it you can see the defects and tell tale signs of machine caused by machining the surface such as sanding and in some even the marks from the rotary veneer cutter or the knife blade as it cuts the veneer for the top layer of plywood.