I am working on a project where I have been given painted letters made of MDF wood that need to be mounted permanently on a wall that is covered with finished ( rough ) pallet wood. One of the requirements is that the letters cannot be screwed onto the wall ( no screws or nails visible ). Since the MDF and wall wood are both painted/finished I figured that regular wood glue is out of the question. Would construction adhesive be the best option for attaching these letters to the wood wall?
There is an easy way using CA glue. But you must be careful not to use excessive amount because it may squeeze out and ruining the finished surface.
The strength of this glueup also depends on the strength of the paint or finishing on both mating surfaces.
There is a possibility the glue will affect the finished surface and ultimately weaken the bonding.
If really strong and lasting attachment is required, consider using wooden dowels. This will require you to mark the back side of the object you want to stick. Transfer the mark on a sheet of transparent plastic and use it as the template to mark the wooden wall. Shallow drill the object and the wooden wall using proper drill bit which will match the dowel's diameter.
One-third depth of the thickness of the object is sufficient for the drilled holes. Use wooden dowel length of two-third of object thickness to connect the wall and the object. You may use tiny ammount of any slow setting glue to strengthen the attachment.
I prefer the second method. Dowels are very reliable.
Liquid nails will do just fine!