Delamination is a common problem with caravan and motorhome floors and as a result the owners of such vehicles have been performing DIY repairs for many years. The main methods of addressing the 'spongy floor problem' which are discussed the most in caravanning communities follow the same basic principals, adhesive is injected into the floor through pre-drilled holes and weighted from above until the adhesive has cured. Two part epoxy resin or one part polyurethane resin are usually the products of choice to repair floor delaminations and while both systems may provide an adequate repair, we believe there are long term advantages to choosing an epoxy resin over a moisture cure polyurethane.
Once fully cured epoxy resin is a very solid material similar in hardness to glass, that will not shrink or expand over time or when ambient conditions change. It flows readily to fill any voids in the floor and then cures at an even rate throughout it's mass until full cure is achieved.
A moisture cure polyurethane (MCPU) curing system is based on a chemistry where the Polyol is activated by an isocyanate hardener which has been reacted with. In this case moisture from the substrates or ambient air around the adhesive kickstarts the isocyanate reaction and begins the cure cycle. Typically carbon dioxide is released by the reaction which causes adhesives of this type to foam or expand during the cure cycle. An MCPU does not cure evenly throughout the mass of adhesive, the outside skin will start to cure first and the isocyanate reaction will slowly progress inwards.
Moisture cure polyurethanes, when used in the joinery industry, are generally applied in thin coatings. When adhesives of this type are used to fill a particularly large void in a floor, either from damage or a pipe being in the floor section, then an adverse reaction could occur whereby the adhesives cures around the outside of it's mass sealing an inner liquid core away from moisture and preventing the adhesive from fully curing. The adhesive within this sealed lump can remain liquid for months until the area is stepped on heavily or a bump in the road may cause the glue bubble to break, at which point the liquid mass will begin its cure cycle again, giving off carbon dioxide and expanding inside the floor.