how to build a floor

[richmusk]

Hi,

 

I am at the stage now where I will be very shortly laying a new floor in my boat. I have the metal supports to support the joists in place and will soon have the ballast laid.

 

I understand that there needs to be a waterproof membraine below the floor to stop damp coming up from the bilge ... how and why is this done?

 

also ... is it wise to insulate ... what with and how much?

 

Does anybody have any advice on how this is done?

How do you fix the floor without nailing through the membarine?

How far apart should the wooden joists be?

Do I need ventalation for the air trapped beneath the floor?

 

Any advice would be good ...

 

Thanks,

Rich

[dor]

I can see why a membrane might be recommended, but I don't think many boats have it. The bilge under the cabin shouldn't be wet.

 

Similarly with insulation, the floor is going to be in contact with the water, which doesn't get that cold (i.e. below freezing), and much of it will be covered with ballast which is probably brick or concrete slabs, which will insulate a bit. Think of the ballast as a storage radiator.

[John Orentas]

Hi Rich.

 

I have never bothered with a membrane of any kind, there is no reason at all why the space below the floor should be at all damp. 20mm shutter ply makes good flooring. Ventilate the space as much as you can to behind the hull side lining and each end if possible but it really is not vital.

 

Screw the floor down with brass or stainless screws as you do on the rest of the boat as you may just need to lift them one day, you rarely have any choice for the beam spacing, but if you do, go a little wider than the standard flagstone you will use for ballast, makes things much easier.

[richmusk]

thanks for that - it will savea lot of time not having to worry about the membraine.

 

Another quickie though ... what would people recommend to paint the bottom of the boat (inside) before the ballast goes in?

[Glennbrown]

Cheap black bitchimen 15 quid B and Q ! Lay flags on correx £40

I went one step further and foamed ballast in to stop any movement

or vibration.

[richmusk]

Cheap black bitchimen 15 quid B and Q ! Lay flags on correx £40

I went one step further and foamed ballast in to stop any movement

or vibration.

25684[/snapback]

 

I wasn't sure whether I needed to use correx as I have horizontal metal beams that are a good 6' off the hull itself so there will be no chance of rubbing. Is this the only reason you were recommending it?

 

I though I would box in the ballast with wood to stop it moving and then use that same wood as the floor joists.

[Guest]

Both our boats have had ballast (common bricks) straight on top of blacking - there should be little or no water down there. Tightly packed ballast should move very little.

[DHutch]

What would people recommend to paint the bottom of the boat (inside) before the ballast goes in?

You defonatly ort to paint the whole of the inside of the boat well before you do any fitting out, its a hell of a lot easyer before you put the floor in!

- Ours was shot blasted, the primed with shot blasting primer and painted with twopot polyureothene.

- Then the paving flags where layed on sheet plastic rolled out over the beams to protect the paint from damage.

 

 

Daniel