Exterior Under floor cracking in sections of ply floor

Boots in Action

Well-Known Member
Mar 13, 2017
Ferny Grove, Queensland
I was doing a check of underneath my Penguin the other day and noticed that the underneath flooring was showing signs of deterioration. Splits were appearing in some sections of the ply floor and some of the outer laminate was cracking away. Whilst these were only small and in the outer layer of ply only, the fact that these small fissures would let water penetrate to the next layer of ply was a concern. We all know what happens to ply material when subjected to water!! Immediate action needed!
From Bunnings, I managed to purchase a 4 litre tub of oil based bituminous paint for $37.00 to waterproof the underneath of the floor and seal up the splits and cracks and any "screw break-throughs" - screws that were too long and had penetrated right through the floor with the inevitable splitting of ply. Then the job of applying same! First coat sucked up a lot of paint as timber was very dry. Fortunately, the van body is higher than normal because of the under slung axle, but still not a fun job. Galvanised frame hard to get around, so it received an occasional splash too as well as my face ( eyes protected by safety glasses). Second coat a lot easier and soaked up a lot less paint which left some more for a third coat. Under floor timber now fully sealed so no water should penetrate to timber in either wet road conditions or creek crossings. Just as well I saw it as the Jayco black covering of the ply is nothing but blackboard water paint sprayed on and never meant to handle the elements that are splashed up underneath. Perhaps other members have had a similar experience or should now have a look at the floor condition underneath their van if timber laminated ply construction? Especially if been through a lot of water or wet roads.


Well-Known Member
Sep 29, 2018
Agree ,even on my 2015 Journey Outback ply was starting to delaminate.Got some water thin epoxy and brushed that on first,into cracks etc then gave it coat of single pack epoxy black.The ply does not appear to be marine ply,just rubbish form ply.


Well-Known Member
Nov 7, 2013
I did similar on my 14.44 and Big Mal, underbody deadener and chassis black mostly, humungous mess underneath as well as me but weatherproof. Chassis copped it but I just sprayed it with silver later on...