Exterior wall on a houseboat

[husbåt]

hi

I'm wondering if I've got this right?

The walls on my houseboat will be 195mm with insulation at 170mm
Description:
plywood(12mm)| insulation(170mm)| weather protection(1mm)| plywood(12mm)

Is that correct??

construction blog: www.ibatteri.com

 

[haavard]

Houseboat or house are certainly similar. That is: air gap between outer plywood and wind protection and (if you have mineral wool in the walls) plastic between inner plywood and insulation.

 

[husbåt]

Houseboat or house is probably the same. So: air gap between outer plywood and wind protection and (if you have mineral wool in the walls) plastic between inner plywood and insulation.

hehe then I've done it completely right =D but about that air gap, is it necessary?? because on my drawing, it's incredibly tight so the air gap would only be about 0.5mm. are there any disadvantages to not having that air gap?

 

[John J]

hehe then I have done everything right =D but what about the air gap, is it necessary?? because in my drawing it is incredibly tight, so the air gap would only be about 0.5mm. Are there any disadvantages to not having that air gap?

You probably shouldn't skip the air gap on a houseboat, the air is likely to become humid.

I would have put minerit on the outermost.

http://www.cembrit.se/Det_finns_5_typer_Minerit-21583.aspx

 

[haavard]

hehe then I did it completely right =D but is the air gap necessary? because on my drawing it's incredibly tight so the air gap would only be about 0.5mm. Are there any disadvantages to not having that air gap?

Then you need to redraw! Either thicker walls or reduce to 145mm insulation.

 

[husbåt]

Then you have to redraw! Either thicker walls or reduce to 145mm insulation.

what is the minimum length for the air gap? is 2.5cm enough?

 

[miry]

If I may express my thought on this, regular insulation is not something I can imagine being suitable in a construction that will be constantly exposed to humidity around 100%, and the temperature will fluctuate, leading to condensation on the walls both outside and inside depending on when it gets cold outside or if it doesn't rise inside. If it is well-insulated, the temperature inside could be low compared to outside, causing condensation on the inner walls as well because there is still inertia in the materials.

So my thought would be to impregnate or oil the wood you will build with thoroughly, so even if moisture enters it, it won't rot or mold, and then use formply or marine plywood for the walls and glue it to the outside, and use Styrofoam as insulation because you don't want anything that can start to mold inside the walls.

If I were to put it together, it would probably become:

Formply (the usual ones don't even have waterproof glue in them)
20-50mm Styrofoam lying completely covering
170-200mm Styrofoam between the stud frame and screw through that layer so you get a "tight" layer
Either the same on the inside, but formply isn't very attractive; marine plywood is nice but not cheap either, or use a breathable material like gypsum that you can paint, allowing any little moisture that gets in to come out

So I would probably skip regular insulation, and the thickness of the middle layer is determined by what the construction requires. There you can also reinforce it to make it rigid since you won't benefit much from the holes of the plywood in this case, but you will get a construction without thermal bridges which is well-insulated, and the insulation capability will remain constant compared to what you will likely get with mineral wool when it absorbs the water, which it certainly will, making it difficult to dry it when it's in a wall.

But that's just my thought.

 

[John J]

so my thought would be to properly impregnate or oil the wood you are going to build with so that even if moisture gets in, it won't cause rot or mold, and then use formplyfa or marine plyfa on the walls and glue it on the outside and for insulation, use foam since you don't want anything that can start molding inside the walls.

so I would, if assembling it with screws, probably do

formplyfa (the usual ones don’t always have water-resistant glue)
20-50mm foam lying completely covering
170-200mm foam between the stud frame and screw through that layer to get a "seal" layer
either the same on the inside but formplyfa isn’t very pretty but marine plyfa is nice but it’s not cheap either or you could use a breathable material like drywall which you can paint so any small moisture that gets in can come out.

I would do it like this, Minerit (IMPORTANT, the frost-resistant variant) on the outside, there’s no better material in a humid environment (sure it’s a bit pricey but it's worth it) then a 2.5cm air gap, after that studs with foam in between (possibly 2 layers if you want to eliminate thermal bridges) and then I would put some wood paneling on the inside to stiffen up the whole build and give a nice marine atmosphere.

today's marine plyfa is not nearly as good as it used to be, the glue is worse and I've seen mold growth on fairly new panels already after 1 year in a damp environment, which you never saw before.

 

[husbåt]

I would have done it this way, Minerit (IMPORTANT, the frost-resistant variant) on the outside, no better material exists in a humid environment (sure it's a bit expensive but worth it). Then liftspal 2.5cm followed by studs with styrofoam in between (possibly 2 layers if you want to eliminate thermal bridges) and then I would have put some wood paneling on the inside to stiffen the entire construction and give a nice marine atmosphere.

Today's marine plywood is not nearly as good as it used to be, the glue is worse and I have seen mold growth on fairly new sheets after just 1 year in a humid environment, which you never used to see.

so how does this sound =D

Mineritskiva Normal | 170mm styrofoam and Impr. stud | Minerit Windstopper | Minerit Fasad

the goal is for this boat to last 5 years at sea at a low cost

 

[Krawk]

Some unusual questions arise for a house.
Where will the boat be located? Could there be water splashes up on the facade? Salt or freshwater?
What movements will occur? Do you need extra reinforcement for these?
How to connect to the deck/hull? Condensation problems there?
etc.

And wouldn't it be wiser to use XPS or PUR instead of regular EPS foam?
I think that closed cells should be advantageous?
Otherwise, it might also be worth considering using steel studs instead of wood.

 

[husbåt]

A bit unusual questions for a house do come up.
Where will the boat be located? Can water splashes reach the facade? Salt or freshwater?
What movements will occur? Is there a need for extra reinforcement?
How to connect to the deck/hull? Condensation issues there?
etc.

And wouldn't it make more sense to use XPS or PUR instead of regular EPS-polystyrene?
I think closed cells should be advantageous?
Otherwise, it might also be a thought to use steel studs instead of wood.

The boat will be located in the Stockholm area. Yes, there can be water splashes on the lowest part of the facade. Freshwater and virtually no large waves. No, it doesn't need reinforcement. I don't have answers for the last part.

Check it out yourself and say what you think
http://www.ibatteri.com/?page_id=47

 

[John J]

so how does this sound =D

Minerit board Normal | 170mm styrofoam and Impr. beam | Minerit Windstopper | Minerit Facade

the goal is for that boat to last 5 years at sea at a low price

Why would you have Minerit inside?

And what would be the point of having both Minerit Windstopper and Minerit Facade??

 

[husbåt]

formplyfa is not as fireproof as minerit: Building board for lightweight walls in demanding environments and as protection for fireplaces/hot installations. Water-resistant, does not mold, surface strong and non-combustible. It is water-resistant and fireproof, and the price difference is only 5000kr and I get a fireproof house in addition.

Minerit Windstopper ensures that wind does not come in and the facade is to make the walls water-resistant, plus I think those boards look nice

facade:
The board is:
• Moisture-resistant
• Fireproof
• Frost-resistant

It does not rot, mold or get damaged by rodents or woodpeckers. Minerit Facade Board is cement-bonded and reinforced with cellulose fibers. The board is alkaline and prevents mold growth.

 

[husbåt]

formplyfa is not as fireproof as minerit:
Building board for lightweight walls in demanding environments and as protection at fireplaces/hot installations. Water-resistant, does not mold, strong surface, and non-combustible. It withstands water and is fireproof, and the price difference is only 5000 SEK, and I get a fireproof house in the bargain.

Minerit Windstopper ensures that wind doesn't come in, and the facade is to make the walls water-resistant. I also think those boards look nice

Facade:
The board is:
• Moisture-resistant
• Fireproof
• Frost-resistant

It does not rot or mold and is not attacked by rodents or woodpeckers. Minerit Facade Board is cement-bound and reinforced with cellulose fibers. The board is alkaline and prevents mold growth.

 

[John J]

Sure, minerit is good for fireproofing, but it's not very attractive to look at indoors, although it can be painted.

If you want the fireproofing, I would have done it like this Minerit board Normal | 170mm polystyrene frame (not pressure-treated as they are not recommended in houses where people will live) | T-Vind Super| Minerit Facade