There seems to be some strange advice around on how to glue T&G boards when using the 'floating installation' method.
what not to do
Recently we have seen how wrongly applying the PVAC wood glue can cause problems - in the short and long run - where the adhesive was applied on the underlayment in front of the already installed row of boards with the idea that installing the next row would 'scoop' up enough glue to bond the boards together.
A) it doesn't and some parts of the T&G will not have enough adhesive, creating a 'weak' link
B) residue glue will be left on the underlayment, bonding part of the boards to the underlayment which can cause obstruction when the wood expands or shrinks
Another 'bright' idea is to apply drops of adhesive instead of a whole length. Again, this will cause many weak links in the construction of your floor.
With the floating method all T&G's have to be glued completely, no two ways about it, no 'saving' money in the short run (and really, bottles of PVAC wood glue aren't that expensive, compared with the costs/time of having to re-install the floor and probably replacing many damaged boards where the T&G's have broken off because of this 'drip and drop' method).
The correct way
So, what is the best method?
A PVAC wood glue bottle comes with an 'adjustable' nozzle. Depending on the size of the groove (narrow, medium or wide) you select where to cut off the nozzle. Remember: you can always go 'bigger', you can never 'knit' it back on.
Hold the board you're about to install in your hand and apply the adhesive in the bottom part of the groove, the whole length of the groove (you'll find your own 'best practice', we normally start at the lowest end of the groove, working our way up). Do the same with the short end groove.
When installing the glued board the sliding movement will spread the adhesive 'around' the Tongue of the board of the row already installed. This is especially important with Wood-Engineered flooring where the Tongue is made of cross-layered wood (pine) which has a more open structure. Not enough adhesive on this open structure could create a weak link.
Any seepage out of the adhesive on the top of the board should be removed with a damp cloth straight away.
As with more installation methods: keep it simple and keep it clean for the best results.
Wooden Floor Installation Manual available now!