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Composite Sheet Sub-Floor


toppy007

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Hi All,

 

Just wondering about using some composite sheets as sub flooring. I've taken inspiration from composite decking. 

 

However this recycled plastic comes in 4 x 8 format at 25mm think. 

 

See link for an example https://www.kedel.co.uk/mixed-plastic-lumber/POB100100025.html?keyword=&matchtype=&network=u&device=c&gclid=CjwKCAiA-_L9BRBQEiwA-bm5fh45y-ypFyjxxPnglnGKZkwe1X0DiVJO1gzjvMf3Ssl75io8npSw2RoCHB0QAvD_BwE

 

I feel its thermal properties and ability to resist moisture make it ideal as sub flooring!

 

But Id love to get your thoughts of using it over traditional Marine-Ply or buffalo board 

 

thanks for any advise

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2 minutes ago, Alan de Enfield said:

Surely a 'sub floor'would be underneath, NOT over marine ply or buffao board.

Haha sorry for my explanation 

 

I saw trying to say, I was thinking of using composite sheet instead of the ply or buffalo board which I've seen commonly used as sub-flooring!

 

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4 minutes ago, David Mack said:

My guess is that this stuff is nowhere nearly as stiff as plywood. So it would be OK if laid over a solid floor, but it will need closer supports than plywood or floorboards if it is to be the main floor in a boat.

Yeah, That's something ill have to consider, and ill dig a little deeper into the young's modulus of the material  

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I have recently looked at recycled plastic for a project, its biggest problem is its thermal expansion which is terrible. If you leave the boat unattended in winter the floor might get down to 0 degrees. On a really hot day it could easily get to 30. You will need to leave big expansion gaps between the boards and fix them down with screws in oversize holes, and not too tight so everything can slide. Anything you put on top will have to cope with this movement too, its just not worth it. Plywood or even water resistant chipboard are much more stable materials.

 

.............Dave

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I would use nothing other than exterior grade OSB  (oriented strand board ) as I have used it for 40 years and never had a problem. Also known as Stirling board.

 

Modern ply is rubbish compared with  the old stuff, even so called marine ply.

 

Definite no-no is MDF.

 

My preferred floor is OSB with real oak T&G on top, totally maintenance free, the more distressed it gets, the better it looks.

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Thanks for the Info 

 

I've been on a couple of narrowboats and all of them have had a damp feel to the floors.

 

Is this normal as plywood will natural absorb the humility from the air?

 

What would the perfect materiel be? a rigid, non-fatiguing, waterprof material with good thermal insulating properties.

 

 

 

 

 

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1 hour ago, toppy007 said:

Thanks for the Info 

 

I've been on a couple of narrowboats and all of them have had a damp feel to the floors.

 

Is this normal as plywood will natural absorb the humility from the air?

 

What would the perfect materiel be? a rigid, non-fatiguing, waterprof material with good thermal insulating properties.

 

 

 

 

 

My boat is dry as a bone. Its 20 years old and, when I fitted a new carpet a couple of years ago, the ply was amazingly like new.

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On 26/11/2020 at 22:12, Richard10002 said:

My boat is dry as a bone. Its 20 years old and, when I fitted a new carpet a couple of years ago, the ply was amazingly like new.

Me2, only bit of damp was due to windows not draining, an easy fix. I do have hot water pipes from stove to calorifier and thence to central heating radiators. Bed warm and dry when stove is on, ie all winter. No need for a hot water bottle, I'm really too warm most nights, rarely wear my wyncyette nightgown :)

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I'm not sure what the advantage of composite plastic floorboards would be? Either you've got wet/damp bilges or you haven't. If your bilges are damp then dry them out. Plastic floorboards aren't going to solve that issue. 

 

The other thing is, as others have said, because the plastic composite has no lateral grain you don't know if it's going to suffer from point loading/creep issues over time and sag under the weight of whatever it's supporting. Alternate grain ply is a dynamically stable proven material so stick with it.

 

My bilges are bone dry by the way.

Edited by blackrose
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On 26/11/2020 at 20:33, toppy007 said:

Thanks for the Info 

 

I've been on a couple of narrowboats and all of them have had a damp feel to the floors.

 

Is this normal as plywood will natural absorb the humility from the air?

 

What would the perfect materiel be? a rigid, non-fatiguing, waterprof material with good thermal insulating properties.

As a matter of interest, what is the problem you are trying to solve? Have you got a boat that you are refurbishing, or have your existing floors rotted away due to damp.

 

Whichever it is, once you have lifted the existing floor, if you do whatever is necessary to stop things getting wet and damp again, plywood will be fine.

 

I have the original plywood, a layer of Cloud 9 underlay, then carpet. Very thermally insulated :) 

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On 29/11/2020 at 00:22, Richard10002 said:

As a matter of interest, what is the problem you are trying to solve? Have you got a boat that you are refurbishing, or have your existing floors rotted away due to damp.

 

Whichever it is, once you have lifted the existing floor, if you do whatever is necessary to stop things getting wet and damp again, plywood will be fine.

 

I have the original plywood, a layer of Cloud 9 underlay, then carpet. Very thermally insulated :) 

Ok cool thanks yes I'm refitting a boat 

 

Guess I was interested at looking at materials that didn't absorb moister to prevent any buildup of damp.

 

I'm happy to use marine ply with a well ventilated sub-floor and a heating system, But I guess I was looking for something to negate the ability of the sub-floor to absorb moisture as you would when looking at properties for a ballasting material.

 

But I very much appreciated everyone's views 

 

Thanks

 

 

 

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13 minutes ago, toppy007 said:

Ok cool thanks yes I'm refitting a boat 

 

Guess I was interested at looking at materials that didn't absorb moister to prevent any buildup of damp.

 

I'm happy to use marine ply with a well ventilated sub-floor and a heating system, But I guess I was looking for something to negate the ability of the sub-floor to absorb moisture as you would when looking at properties for a ballasting material.

 

But I very much appreciated everyone's views 

 

Thanks

 

 

 

OSB will soak up gar less water than plywood.  At less cost.

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I don't know much, but I get the impression modern OSB is often used outdoors on building sites and for jobs where it needs to be reasonably weatherproof. In the beginning it was let down by the adhesive/glues, but now it's OK. I've seen it used in the construction of NB linings, a bit too rustic for my liking ......

I do know there is plywood, 'marine ply' and 'Real Marine Ply', can't remember the specs offhand.

Edited by LadyG
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