Not all engineered flooring can be installed the same. Some are designed to be stapled, floated, or glued down, the milling on the T&G joint is good enough to use glue in the groove, and strap clamps, to glue the assembly together with T&G glue only so it all floats. You can staple it and not have loose or high/proud edges, from the groove side. Some engineereds are gluedown only. They are not milled well on the T&G. Gluing it all down keeps it pretty flat, with some patients. Some engineereds are floating only. These have the glueless locking T&G joints.

Thanks for the advice. Since I was recently diagnosed with Asthma I am very concerned about the irritants. At this point, I am pretty surre I am going to change my mind about the glue-down and go with an alternative. What do you think about a floating floor? I know my contractor is not a big fan of it..he says it shifts and doesnt feel that great underfoot. Is it much less expensive to install then a nail down? Thanks so much for your advice, it is greatly appreciated. Melanie

No advantage in using a nail down product. There are many quality engineered floors on the market today that have the same durable finish as the solid hardwood products.

Manufactured flooring generally has a harder finish than site installed/finished hardwoods. Laminate flooring is generally thin, made to lock together(some lock well, some do not), and cannot be refinished. Most damage is permanent and replacement is necessary to fix. Engineered flooring has layers of material, the last or top layer being the wear layer. Cancook's explanation is referring to those better grade types with a 6mm wear layer, instead of a thinner(3-4mm) wear layer. That wear layer is made up of chemicals and minerals to form a very tough surface. This type can be installed by nails/staples, glued to the surface, or as a floating floor. It is thick enough to be able to be resanded/refinished is desired. Site finished hardwood flooring is installed using tongue and grooved planks(from 12" to several feet long) that are unfinished wood. Each plank is nailed/stapled to the sub floor(using an underlayment like tar paper/craft paper/rosin paper/etc. to prevent squeaking). Then the entire surface is sanded flat, cleaned of dust, and a finish(oil or water based for most applications) of three or more applications are applied. Solid wood has enough thickness to be refinished(sanded and new finish applied) at least once with fairly major damage and may be refinished twice. Many homes built in the early 1900's have repairable solid wood flooring. One other item. Click together flooring has zero water resistance. Water can easily get between the connections and through the flooring. The connections for nail down engineered flooring are a lot tighter and more water resistant since the process of nailing forces the planks tighter together. Site finished wood flooring has an unbroken surface since the finish is applied in layers. Take a 14' by 18' room as an example. Laminate flooring could be installed in two or three hours and immediately ready for use. Engineered flooring might take the entire day(8 hours), and be immediately ready for use. Solid wood would take a minimum of 2&1/2 days to install(nail down, sand, three coats of finish with 6 hours between applications---oil based would be another 24 hours for finishing) plus a waiting time to walk on, then move furniture and even longer for area rugs.