Jump to content

Roofing felt - why?


Featured Posts

On excavating down to the bottom of my boat - having taken up the floorboards and removed the ballast (concrete paving slabs), I then had to peel away a nasty, sticky mess of roofing felt. I can understand that it was there to protect the metal against water, but it hadn't - so also had to remove scale rust.

Why roofing felt? This isn't a load-bearing material.

Should the ballast have been laid differently?

Are there any alternatives - like Butyl pond liner?

 

Thanks for looking, appreciate any responses. Bear with me if I need explanation - newbie.

Link to comment
Share on other sites

On excavating down to the bottom of my boat - having taken up the floorboards and removed the ballast (concrete paving slabs), I then had to peel away a nasty, sticky mess of roofing felt. I can understand that it was there to protect the metal against water, but it hadn't - so also had to remove scale rust.

Why roofing felt? This isn't a load-bearing material.

Should the ballast have been laid differently?

Are there any alternatives - like Butyl pond liner?

 

Thanks for looking, appreciate any responses. Bear with me if I need explanation - newbie.

 

 

Yeah, ends up a right mess in most cases and if water does get to the bilges it will end up getting trapped between the felt and ballast.

 

When we ballasted all the 2 x 2 slabs were laid on strips of solid plastic, (offcut strips from double glazing) These keep the ballast off the base plate and a decent air gap between. Should any leakage occur, water will flow easily to the stern and dry out quickly between ballast & base plate. There's also good air flow.

 

We accessed our bilges just last week, first time for 6 years so didn't know what to expect.

 

Happy to see this though.

 

DSCF2879_zps50deb767.jpg

 

No damp or musty smells either. I always intended to put an accessible hatch in this area but prioritised other things. Might well do so now.

Edited by Julynian
Link to comment
Share on other sites

As Richard says it's supposed to stop the ballast scratching the protective paint off the baseplate, but the flip side is should any water get down there it is going to take an age to dry out, if it ever does.

 

I think I'm right in saying that in the days when boats were built with "wet" cabin bilges, the floors had longitudinal L section strips which held the concrete slab ballast clear of the baseplate. This method was still used, and probably is still used in some boats even though all boats now have dry bilges. It seems to me to make a lot of sense though it doesn't work if you are using brick ballast.

Link to comment
Share on other sites

Funny that,

When I built, I used roofing felt (as I didn't know any better) as an alternative to waxoil which seemed nasty and sticky. I didn't know it was a general practice.

'twas several years ago.

 

Link to comment
Share on other sites

Like Julynian my ballast is laid on spacers, I didn't have access to plastic spacers at the time and just used 1/2" batten.

The ballast itself is mixed steel block and pig iron and after about 15 years all is still fine there although I have had a couple of minor floods due to plumbing problems. The raised ballast allowed a good air flow (aided by a fan heater)to dry the bilges quickly and thoroughly boat.gif

Link to comment
Share on other sites

As Richard says it's supposed to stop the ballast scratching the protective paint off the baseplate, but the flip side is should any water get down there it is going to take an age to dry out, if it ever does.

 

I think I'm right in saying that in the days when boats were built with "wet" cabin bilges, the floors had longitudinal L section strips which held the concrete slab ballast clear of the baseplate. This method was still used, and probably is still used in some boats even though all boats now have dry bilges. It seems to me to make a lot of sense though it doesn't work if you are using brick ballast.

 

My first boat had a wet bilge and the slabs were just laid directly on the baseplate.

Link to comment
Share on other sites

From what you've all said, I reckon that my best bet is to go with using a protective layer of primer/paint, then plastic spacers on which to lay my ballast, as it's concrete slabs.

 

I'm thinking that time / movement probably caused the old felt layer to fail. Now that the metal is no longer smooth due to the corrosion, a new layer would be more of a potential water trap.

 

Thanks all.

Link to comment
Share on other sites

  • 2 years later...

Hello All,

Me and my girlfriend are currently in the same position with our narrowboat that Sir Percy was in back in 2014. Just wandering if anyone could recommend anywhere that we could get some plastic spacers that would work to create this ventilation gap between the bilge and the ballast - have been scouring the interweb and can't really find what we want.

Many thanks.

Link to comment
Share on other sites

 

another option I have seen used is the pipe clips for 15mm pipe

Link to comment
Share on other sites

use an old hosepipe cut into about 3inch lengths, alternatively get hold of some old twin and earth cable and cut that up to use as spacers

 

If there is any wet, won't the copper in the cable cause problems.... i.e. dissimilar metals

Link to comment
Share on other sites

If there is any wet, won't the copper in the cable cause problems.... i.e. dissimilar metals

Yes, it will become a copper/iron battery, but only if the water in the bilge is deep enough to cover the copper. If the two dissimilar metals are kept apart all will be ok, although personally I would use plastic as spacers.

 

See the bit about the statue of liberty in the attached.

 

https://en.m.wikipedia.org/wiki/Galvanic_corrosion

Link to comment
Share on other sites

Hello All,

Me and my girlfriend are currently in the same position with our narrowboat that Sir Percy was in back in 2014. Just wandering if anyone could recommend anywhere that we could get some plastic spacers that would work to create this ventilation gap between the bilge and the ballast - have been scouring the interweb and can't really find what we want.

Many thanks.

 

You might have timed this just right - I don't mean picking up on a thread two years old, I mean we're just now getting some hot, dry weather after a wet summer. I think it was like this when I was looking around for material to go underneath the ballast. What I found was quite a few garden hoses being chucked out by people needing to do a bit of a watering and finding that theirs was old and knackered.

Good luck!

Gav

Edited by Sir Percy
Link to comment
Share on other sites

Old fan belts cut into 1" pieces are excellent spacers. I think rubber is better than plastic, less chance of vibration. Also, waxoyl tends to dry out over time and becomes crusty, any water then gets trapped under the waxoyl and retains the dampness in the bilge. Undesirable.

Link to comment
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
  • Recently Browsing   0 members

    • No registered users viewing this page.
×
×
  • Create New...

Important Information

We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue.