Houseboat insulation floor, floor construction

Hello everyone,

I am currently converting a houseboat and have a question about the floor construction, especially regarding the insulation.

The entire house is built using timber frame construction, and the floor currently consists only of OSB panels. Now I want to lay insulation on top of it and ultimately laminate flooring above that. For the insulation, I was thinking of XPS rigid foam boards (50mm or 60mm). Now my question is: does a vapor barrier need to be installed somewhere in between, and can laminate be laid directly on the insulation? Do I need to install edge insulation strips all around? What floor construction would you recommend to me? Please ignore the water stain in the picture; the roof is now watertight;-)

What is underneath the OSB? Outside air or ventilated area? It won’t be directly in water like that, right? Regarding XPS: You cannot lay flooring directly on it, especially no laminate or vinyl; a load distribution layer is needed, otherwise, you’ll punch a hole in it with the first kick. Vapor barrier: On the inside (the warm side) always more vapor-tight than on the outside (exterior wall or floor surface). Or your insulation is capillary active and vapor-open, so moisture can dry back inside. In your case, you have "outside" OSB. That has a relatively high vapor-retarding effect. The options remain either OSB or tighter on the inside as well, or everything open and made of wood + wood fiber. Either: Battens with wood fiber soft boards in between or jute, and parquet planks on the battens. Or: EPS DEO with >150 kPa compressive strength and dry screed boards or also OSB boards on top, and then laminate/vinyl/parquet. You can also use XPS, but it’s more expensive. For the wall, I would use compressed mineral wool and a vapor barrier inside and OSB sheathing. Even better is to put about 6 cm battens with compressed mineral wool inside in front of the vapor barrier and then OSB before that. Then you have an installation cavity and the vapor barrier is not pierced. The roof is the same. Edge insulation strip with EPS + dry screed makes sense if the battens are to be laid floating (to prevent warping) that also makes sense.

What is under the OSB? Outside air or ventilated area? It won't be directly in water, right? Regarding XPS: You can't lay a floor covering directly on it, especially not laminate or vinyl; there needs to be a load distribution layer, otherwise you'll punch a hole in it with the first kick. Vapor barrier: Inside (warm side) always more vapor-tight than outside (outer side of wall, floor). Or your insulation is capillary-active and vapor-permeable so moisture can dry back inside. In your case, you have "outside" OSB. That has a relatively high vapor-retarding effect. The options left are either OSB or tighter on the inside as well, or everything open and made of wood + wood fiber. Either: battens with wood fiber soft panels in between or jute and parquet planks on the battens. Or: EPS DEO with >150 kPa compressive strength and on top dry screed boards or OSB boards and then laminate/vinyl/parquet. You can also use XPS, but it is more expensive. For walls, I would use compression fleece with vapor barrier on the inside and OSB sheathing. Even better is to put about 6 cm battens with compression fleece in front of the vapor barrier inside and then OSB in front of that. Then you have an installation space, and the vapor barrier is not penetrated. Roof the same way. Edge insulation strip with EPS + dry screed makes sense if the battens are to be laid floating (to avoid warping). That also makes sense.

Thanks for your detailed answer first of all. Exactly, outside air is under the OSB. After about 50 cm comes the water. I think I prefer the variant with EPS and then OSB on top. I just have to check if the weight is okay. The boat weighs about 5t without the interior fit-out, I still have about 2t available for the complete fit-out. It'll work ;-)