Veneer is basically a thin layer of timber that’s glued onto a ‘core’ usually the thin layer is the timber finish desired and the core is usually a cheap softwood, this creates a cost effective product for customers on a tight budget. This veneer will achieve a similar appearance as the real product once stained, the glue also gives the compound stability and strength.
Solid timber refers to the products being the same timber throughout the product, this creates a higher quality of product with feel and lasting appearance. Most hardwoods used for joinery will already be highly durable and usually they are manufactured using lamination which permanently bonds 3 pieces of the same timber together creating a highly stable end product which produces lasting performance.
The difference becomes a lot more noticeable when discussing maintenance, where solid timber will need maintenance mostly for appearance, veneered timber will need maintenance for the integrity of the compound, as without proper care the glue between the core and the veneer can weaken. This is due to the veneer expanding and contracting with the environment at a different rate to the softwood core, creating tension within the product.