Replacing Aft cabin Sub Flooring

Hi, I need to replace my sub flooring in my aft cabin of my MT34 any ideas would be great also I think I may need to do the v berth sooner or latter** Thanks Dom

So what's there now?

Rotted plywood subflooring and teak parquae floors

We were on a boat a few weeks ago that had replaced all of the flooring in the galley and the main cabin with teak and holly plywood.* It looked great.* I think this is simlair.

http://www.jamestowndistributors.com/userportal/show_product.do?pid=51940

Same boat, same problem.* Since mine's 38 years old, I decided just to cover the floor with 1/2" exterior plywood, and cover that with a berber-style carpet remnant I got at the Big Box. I got some binding for the carpet edges, looks pretty good, to my less-than-perfectionist eye.* The salon and fwd cabin decks are ok. Looks to have been old water damage from before the windows were replaced. Not a lot of traffic back there anyway.

*

Don't use exterior plywood. It is generally crap. Marine grade plywood is the way to go. It is much stronger and wont try to curl up. It is more expensive than exterior grade plywood but this is a one time expense. Find a local cabinet shop and they can usually tell you where to get marine grade plywood at a decent cost. 3/4" should be under $100 per sheet. If you go to a local lumber yard you will probably pay twice that. Buy marine grade at a specialty lumber yard - they will be cheaper than you think.

Thanks, Tony. This isn't a "permanent" fix of any kind. Not even screwed down. Just something to keep the floor stable enough for carpet and to walk on. I do not think the subfloor is structural, is it? There's really only one spot that's really soft, near the head door, but I laid the plywood down over the whole floor just to keep it even.

As long as, it isn't constantly exposed to water,*it should be fine. *Be sure and*check it over for obvious flaws. *But don't buy something like a poor quality CDX (common house subflooring). *One side will have cracks and open knot holes. *I got a couple of sheets in a bundle recently, where the internal voids, cracks/splits all came together and it was very weak.

Use exterior grade, it is made with phenol-formaldehyde based glue and is water resistant. *I would still seal it to protect it from moisture though.

Larry B

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-- Edited by Edelweiss on Monday 22nd of August 2011 09:16:40 PM

Exterior plywood will be fine. Marine grade is just exterior grade with no flaws for better looks.

Marine grade plywood is bonded with the same glue as exterior plywoods.* The difference is that the voids in the cores are plugged or patched to give a core with no voids* This makes it stronger to endure more stress.* For a floor underlayment, their is an underlayment grade that has the first two cores solid to pevent heel penetration.* It comes in nominal 5/8' and nominal 3/4' thickness.* Their faces are plugged and touch sanded.* There is also a nominal 1/4" luan floor underlay and an MDF underlay.* You will pay a hefty premium for marine grade plywood that is meant for hulls and stressed bulkheads.

In many farm locations the feed stores will sell wood to use as fencing.Can be chewed ,by farm critters, unlike treated wood.

Forget if its cedar or cypress , but its cheap and usually fairly nice wood in terms of grade.

This would make a fine planked floor , sanded and oiled , it would be grand.

The last sheets of "teak & holey" we purchased were 3/4 thick , but the overlay was so thin , I doubt it could be refinished even once!

The current "teak & holey" is testimony to the ignorance of the purchaser for 50 years.

A classic teak and holy flooring has the holey proud about 1/8 of an inch to serve as no skid.

Weather plywood is "better grade" is simple , count the ply's .

a piece of 3/8 ply that is 5 or half inch of 7 layers is FINE.

I want to replace the entire floor but need ideas on getting under the beds and cabinets DOm

I would use MDO one side plywood. It is usually nicer than exterior grade and has the smooth craft paper inpregnated in it. This product is made for road signs and is made to be constantly wet/dry. Cost is about
$32/sheet in 3/8" size. It comes in 3/8 and 3/4", sold at every lumberyard . NOT to be confused with MDF.
I have built skiffs out of this stuff with excellent results. Prime it with kilz, paint with exterior latex house paint and your in biz-cover with carpeting or your choice of flooring!


-- Edited by Sailor of Fortune on Thursday 25th of August 2011 06:47:16 AM

Dom61 wrote:
I want to replace the entire floor but need ideas on getting under the beds and cabinets DOm

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*Sounds like you have an ambitious project!* I assume you've tracked down and fixed the leaks that caused the damage in the first place.

I have already replaced the entire back wall and the roofs were done before I got the boat so I believe that has been done

Second the MDO, the stuff is great but heavy! Built new style bars on the last boat out of the 1".

"Second the MDO, the stuff is great but heavy!"

Remember the area under the cabin sole will at times be awash, with bilge water with oil.

I am not convinced MDO long term useful here.

Take a cut off and boil it for an hour and see if at least the glue is OK.

You can replace the wood under the bunks and the floor by using 3 pieces of marine ply -- and fiberglass tape. Start with the larger bunk on the starboard side, rip out everything but the outer cabinet frame and you can slide the new wood under the existing frame. You'll probably have to raise the stringers a bit by laminating a small strip on top of them.

You probably have a wet, stinky balsa sandwich on both sides where the floor meets the hull, get rid of that and fiberglass the new floor right to the hull...

Do the other side the same way. You end up with one seam not taped on the main sole - (as that would leave a high spot), fill that with epoxy/filler paste and sand smooth. Then lay whatever flooring you want.

This is also your one and only chance to replace water lines to the tanks, and run the wiring to the stern light...

It can be done, good luck.

ARoss said:

Thanks, Tony. This isn't a "permanent" fix of any kind. Not even screwed down. Just something to keep the floor stable enough for carpet and to walk on. I do not think the subfloor is structural, is it? There's really only one spot that's really soft, near the head door, but I laid the plywood down over the whole floor just to keep it even.

Click to expand...

I would assume that it is structural unless I had it from a reliable source that it was not. I would remove any damaged wood, check what is beneath it, and replace any damaged structure, subfloor, and flooring with equal or better quality materials..

That's just me though, I have learned that it's easier and less expensive to make a repair the right way the first time.

@rwidman - The Floor isn't structural. The stringers on the walls, that help support the decks between the aft engine room bulkhead and the lazerrate bulkhead - they very much are - they contribute to supporting the weight of the aft cabin itself.

This is a boat with a 3/4" solid fiberglass hull from the waterline down, that's what the floor is sitting on.