Solid or Engineered?

Hardwood

As the name implies, solid hardwood is solid wood, all the way through. 

Engineered hardwood flooring is done in layers.  The top layer is a hardwood veneer and then beneath that, there are layers (or plies) of wood.  Generally, these plies are perpendicular in direction and layered together. Generally these plies are made of wood although they are not necessarily the same species as the top layer. The thickness of the top veneer can vary, and generally higher quality engineered woods have a thicker top layer, and cheaper ones have a thin one.

Solid hardwood expands and contracts more, especially in wider widths.  (Note: all hardwood expands/contracts based on humidity).  With wider widths, especially 5 inches or wider, it’s important to both nail and glue the flooring for less movement. 

Engineered hardwood is often more stable.  Because of its layers, it’s often stronger than solid hardwood.  And, because the layers are perpendicular to each other, there is usually less expansion and contraction, so it allows for a tighter fit, especially during the winter when it is dry.  In addition, because it’s more stable, you can often go wider in the planks.