Fitting of a floor in a sailaway.

[Mark R]

Hi all,

 

I have to all intents and purposes a sailway boat that I’m renovating. I’m wanting to get a floor down and would appreciate some advise as to what are the best practices relating to this.

 

There is currently ballast (concrete sleepers and block paving bricks), the ballast is higher than the steel ribs, so I have secured 2x2 inch timber over each rib to increase the height beyond the ballast. My question is, should I be insulating beneath the floor or is this a potential issue should there be a leak under the floor? If insulating is good practise I was thinking of using 25mm Kingspan (or similar).

 

The floor would be either 18mm ply or reclaimed/seconds scaffold boards. If using ply as a subfloor should this be marine grade or is that overkill? Do any of you foresee issues with using scaffold boards as a finished floor?

 

Any suggestions or thoughts are appreciated.

 

Mark

[BEngo]

2 or 3x2 timber on the bearers is common.  It should be treated timber.

 

Insulation is not common, but closed cell polyurethabe type sheet (celotex) will not absorb water if there isxa flood.

 

Ventiation below the floor is essential as are hatches to check what is happening.  One at the back will enable you to get at any water that has run along the bilge.  Using a fridge fan to draw air through the bilges is a good trick.

 

18mm Good-One-Side ( shuttering ) ply is a good and common  floor material.  Scaffold boards are too likely to move independently of each other as the weight comes on,  unless you groove the sides and fit a loose tongue.  They are also rough edged so wont fit closely together.  They would be all right iif finished up neatly and laid over a ply or OSB floor.

 

N

[LadyG]

I would think that adding two inches on the bearers plus three inches of scaffolding would reduce the effective height by five inches!

Regarding ballast, when I moved on  my narrowboat it was a bit "tippy', a bit high in the water, by the time I got all my books, clothes, tools, coal, water, and diesel, loaded up it settled in nicely.

[Tracy D'arth]

Your battens on top of the steel angles must have cut outs in them otherwise you have no ventilation under the floor other than possibly the small limber gaps in the angle iron at the side which are to let water flow backwards.

OSB is fine for floors, better than most modern plies which are poor.

Scaffold boards are overkill and rough.

Edited March 10 by Tracy D'arth

[David Mack]

17 minutes ago, Tracy D'arth said:

Your battens on top of the steel angles must have cut outs in them otherwise you have no ventilation under the floor other than possibly the small limber gaps in the angle iron at the side which are to let water flow backwards.

Fit the battens running fore and aft so there is through ventilation. You may need to adjust a few of the top layer of ballast blocks.

[Mark R]

Cheers guys, really informative. I didn't use treated timber for the battens, is that a real issue? It's not the end of the world if I need to pull it up and replace it, it can be reused elsewhere in the project.

Edited March 10 by Mark R

[blackrose]

 

1 hour ago, BEngo said:

Insulation is not common, but closed cell polyurethabe type sheet (celotex) will not absorb water if there isxa flood.

 

Most PU foam has a small % of open cells but that's not really the issue. I really don't think it's suitable to be laid under ballast where it could potentially be exposed to moisture for an extended period. Plus the weight of the ballast could cause the foam to "creep" and compress over time rendering it useless.

 

If you want to insulate the floor you'd have to find some way of insulating directly underneath the subfloor on top of the ballast, however I don't think it will be very effective. If you're having a wooden floor then the specific heat capacity of the dense hardwood will give you a cold floor in winter whatever you put underneath (likewise for a laminate floor). If you choose carpet then you may as well insulate on top of the subfloor with a decent underlay. 

 

So personally I wouldn't bother with insulation under the subfloor, just make sure there's an air gap.

 

21 minutes ago, Mark R said:

Cheers guys, really informative. I didn't use treated timber for the battens, is that a real issue?

 

I don't think mine are treated timber? I might be wrong but it just looks like normal pine to me. They've been there since 2005 and are still fine. I've cut several inspection hatches and never seen any problems, however apart from a few small leaks my bilges have always been dry. If your bilges remained wet for a prolonged period then it might be a different story I suppose.

 

*Although you should lay your ballast on old cables or plastic spacers, etc (to help any water flow to the back of the cabin where it can be removed and to prevent water getting trapped under the ballast), and people here will tell you to treat the underside of your subfloor, etc, etc... in fact the most important piece of advice is to try to prevent water getting down into the bilges in the first place. Avoid leaks, switch your water pump off when you go out, fit your water pump in a washing up bowl and place the sensor of a 9v battery operated water level alarm in the bowl. Of course over the years some water will get down there, but these measures will reduce the likelihood of damp bilges.

Edited March 10 by blackrose

[PaulJ]

19 minutes ago, David Mack said:

Fit the battens running fore and aft so there is through ventilation. You may need to adjust a few of the top layer of ballast blocks.

A better way to do it. Mine are done like this- the other advantage is with a bit of planning all your bulkheads/kitchen units etc can sit directly on them which makes having almost all of the floor removable a doddle. Alot of extra work though.

[TandC]

My boatyard recommended I use a subfloor that was 25mm plywood rather than 18mm plywood as they said modern ply is a bit crap and flexes.  I bit the bullet and spent the money and I am glad I did - there is no "bounce" or flex - and i'd be confident of sticking LVT flooring to it directly.   

 

As a result I have a load of 18mm structural ply going spare if anyone wants any!!  

[system 4-50]

I fitted 25mm ply as flooring to my sailaway, very pleased with its solidity.

[blackrose]

My floor flexes in a couple of places but I don't think it's because it's 18mm ply, I think it's because it was never fitted properly. They put a double layer of broken paving slabs in the bilges to provide enough ballast for my boat (I calculated about 8 tonnes) and in some places the underside of the subfloor barely clears the top of the ballast. The floor is uneven so I think it must be touching the ballast at a couple of points. 

 

Is there any way of leveling it off at the high points with a plane or something so that I could fit LVT or something other that carpet, or do those parts of the floor need to come up and be fitted properly?

[Tracy D'arth]

4 minutes ago, blackrose said:

My floor flexes in a couple of places but I don't think it's because it's 18mm ply, I think it's because it was never fitted properly. They put a double layer of broken paving slabs in the bilges to provide enough ballast for my boat (I calculated about 8 tonnes) and in some places the underside of the subfloor barely clears the top of the ballast. The floor is uneven so I think it must be touching the ballast at a couple of points. 

 

Is there any way of leveling it off at the high points with a plane or something so that I could fit LVT or something other that carpet, or do those parts of the floor need to come up and be fitted properly?

Floor self leveling compound, powder and water mix, pva the wood first and lay whilst still tacky. But you will have to have the boat dead level first else it will all flow down to one end!

[matty40s]

We had 2 boats in for floor replacement in January/Feb. Both had experienced long term under floor water problems which wasnt dealt with. Retro fitting flooring is far more difficult than putting down new, as everything is built on top of floor, cupboards, steps, toilet , sink units, showers, etc etc. 

 

 

[blackrose]

35 minutes ago, Tracy D'arth said:

Floor self leveling compound, powder and water mix, pva the wood first and lay whilst still tacky. But you will have to have the boat dead level first else it will all flow down to one end!

 

Well that's not an option as a boat floor is seldom dead level. Mine isn't anyway, it rises towards the bow. In terms of getting it level I'd need massive loads of ballast. Even filling my water tank doesn't really do it.

Edited March 11 by blackrose

[ditchcrawler]

11 minutes ago, blackrose said:

 

Well that's not an option as a boat floor is seldom dead level.  

It will be if you use self levelling compound, probably 6" thick at the stern and ¼" at the bows 😁

[MtB]

On 10/03/2024 at 15:18, Mark R said:

There is currently ballast (concrete sleepers and block paving bricks), the ballast is higher than the steel ribs,

 

 

This bothers me slightly. If there is too much ballast and some needs removing to trim the boat, you are stuffed once you've laid the floor.

 

Is your boat on hard standing or in the water while you are doing this work?? 

 

 

 

 

[blackrose]

11 hours ago, ditchcrawler said:

It will be if you use self levelling compound, probably 6" thick at the stern and ¼" at the bows 😁

 

That's one way of doing it I suppose!