Dresser carcass wood design, plywood or secondary hardwood (wood movement issue)

[kooshball]

I am still in the final planning stages with my next project, a wide walnut dresser. I plan to use vertical grain solid walnut sides joined to the top and bottom carcass with half blind dovetails. I was originally planning to use plywood for the top and bottom carcass since it is quick and is not shown on the final piece. I am concerned however that the plywood will not move seasonally with the walnut that it is dovetailed into and that I will have joint failure or splitting of the walnut.

The depth of the dresser (width of the walnut) is going to be between 20" - 21" so the question is: should I go forward with the plywood plan or substitute something cheap like poplar that will move with the walnut seasonally?

Thanks for the help.

 

[JimD]

The traditional answer is that you do not join solid wood to plywood or mdf. You know the reason. I have done it on a kitchen island and a large dresser in oak, however. Both are several years old with no problems. I did not do what you describe but it amounts to about the same thing. My carcases are a mixture of plywood and solid wood but in the form of flat panels to make up the ends of the island and dresser. The top of the dresser is solid oak. The island is granite supported by plywood. The part of these pieces that I think is similar to your concept is the drawers.

I make drawers of 1/2 baltic birch plywood. But the front of each drawer is solid wood. Oak for the dresser and cherry for the island. The sides of the drawers are half blind dovetailed into the solid hardwood drawer front. The back and bottom of the drawers are also plywood. The drawers are finished in poly which helps to inhibit mositure movement. I think that is key. If I had used an oil finish that was more easily penetrated by moisture I think I would have gotten splits. Because the wood is well covered with poly, the drawers hold up fine. I think it also matters how big a humidity swings the pieces see. Humidity varies widely in SC but the pieces never see the full swing. In a dryer climate, the risk would be even lower.

Jim

 

[Gofor]

From experience, the walnut will move over 1/8" at that width. It will cause problems if dovetailed to a ply top or bottom. You say the carcass top will not be visible. If the visible top is also solid walnut, why not just dado the side into the visible top? The grain will match a vertical side and will expand accordingly. No need for a solid "carcass" top. Face frame stretchers for the front will have long grain running along with the top (no cross-grained issues) and the rails will also match the sides.

If the visible top is to be granite, stone, etc, (i.e not solid wood) then the sub-top only needs to be narrow boards on front and back which will not cause wood movement issues. (basically like kitchen cabinet construction). Top attachment is solid in the back but slotted in the front to allow the case to move.

Not sure what your design is, so having problem seeing the need for the ply "carcass" top/bottom.

Go

 

[kooshball]

Thanks guys. I am going to go with poplar for all the secondary lumber as it is cheap and has similar moisture expansion rates as walnut.

The reason for the sub top was just to add strength. The piece will be around 60" wide and may need to support our 42" plasma TV.

 

[Gofor]

If you are going to have any internal framework (i.e. to mount drawer slides to, as a cabinet wall with front door access), that should provide all the vertical support needed for that size if the top is 3/4 thick or better.

Go