Raising the roof

[Redfox]

Need some advice here.

 

I bought a cheap NB unseen with a view to a complete tearout and refit. Walls and roof are plywood. The ceiling height is only just about 6' in the centre, and certainly not high enough for me to walk around without stooping. How practical is it to raise the roof height? I was thinking I could detach the roof from the walls then install taller wall panels then reattach the roof. Is that doable, or am I off my head?

 

If the latter, any suggestions how to gain some additional ceiling height?

 

[Tracy D'arth]

Put a new steel top on it? Its a lot of work to raise the existing and make it solid enough.

[Ken X]

Be cautious, there are some loooow bridges out there.  When you have to remove the tiller pin, things are getting tight. 🙂. 

 

There is lots of good advice on this forum, hopefully you can sort it another way.  What's the floor construction like and how much headroom are you after?

[Bod]

8 minutes ago, Redfox said:

Need some advice here.

 

I bought a cheap NB unseen with a view to a complete tearout and refit. Walls and roof are plywood. The ceiling height is only just about 6' in the centre, and certainly not high enough for me to walk around without stooping. How practical is it to raise the roof height? I was thinking I could detach the roof from the walls then install taller wall panels then reattach the roof. Is that doable, or am I off my head?

 

If the latter, any suggestions how to gain some additional ceiling height?

 

"Walls and roof are plywood"  Is this only on the inside, or is this a wooden top boat?

Certianly it is possible to raise the roof level, or change a leaky wooden top for a steel cabin.  Whether the cost is worth it, is the question.

This might be, just tidy up and sell on.

 

Bod

[Redfox]

5 minutes ago, Ken X said:

Be cautious, there are some loooow bridges out there.  When you have to remove the tiller pin, things are getting tight. 🙂. 

 

There is lots of good advice on this forum, hopefully you can sort it another way.  What's the floor construction like and how much headroom are you after?

I'm looking to add 3-6". It's an old boat and is noticeably lower than many in the marina. It's a complete tearout and refit, so floor construction can be tailored.

[Redfox]

2 minutes ago, Bod said:

"Walls and roof are plywood"  Is this only on the inside, or is this a wooden top boat?

Certianly it is possible to raise the roof level, or change a leaky wooden top for a steel cabin.  Whether the cost is worth it, is the question.

This might be, just tidy up and sell on.

 

Bod

It's a wooden boat top. I'm guessing a steel cabin would be expensive. Too late for a 'tidy up and sell on' I'm afraid - the insides were a mess so I've stripped them out

[Tony Brooks]

I fear that once you start to remove the side panels, you will find rust and perforation in the hull parts. This could easily go out of control. Even if you intend to take the roof off the sides, I fear you will find rot, thus making the job far longer and difficult than you envisage. Sorry to be a pessimist, and the best of luck with it.

[howardang]

Be cautious of adding extra weight especially to the roof. You could seriously compromise the reserve of stability without thinking of this issue and you may find that you may have to add weight i.e ballast low down to compensate, which could then increase your draught.  Discuss it with the boatyard before proceeding.

 

Howard

 

 

[Stroudwater1]

A friend replaced their GRP roof with steel. It’s been a very good result and their old Harborough boat looks similar to how it did even with the louvred windows preserved. A good boatyard should be able to advise. His was done at a well known yard with a tall crane near the River Severn. 
 

it would probably be a worthwhile investment but then we don’t know what your boats hull is up to. Good plywood is very expensive now but sadly I think steel is too. 
 

The difficulty as Tony says is that wood GRP and steel all expand and contract at different rates so leaking seems are pretty inevitable with the set up you have. 

[Bod]

Does anyone remember the thread where a wooden top was taken off, and bigger taller up stands were welded to the gunnels?

I've tried to find it, as it would show how the top is fixed to the hull, and the amount of work involved.

 

Bod

13 hours ago, Redfox said:

It's a wooden boat top. I'm guessing a steel cabin would be expensive. Too late for a 'tidy up and sell on' I'm afraid - the insides were a mess so I've stripped them out

The wooden roof and sides, how good or otherwise is the quality of the joints, and methods of construction?

Chippy grade, butt joints and nails.

Carpenter grade, some angle joints and screws.

Thru to

Cabinet grade, no visible joints, brass screws (with slots all lined up) and varnished.

 

Bod

[Tacet]

I would not have taken this boat on, as it is too much work for me.  But if I was in you position with a wooden top that needed to be raised (rather than replaced) I would at least consider adding the extra bit on the bottom end of the cabin sides.

 

Run around just above the gunnel with a circular/reciprocating saw, lift the top off in one piece. This removes the scruffy lower edge of the cabin, which is the most likely area for rot.  It will also allow you to get at the steel wood interface where leaks and rust abound.  Weld a new steel upstand to give the extra headroom and reassembly is then the reverse of removal.

 

What it will look like, I'm not sure but same applies to increasing the height at the top.    Quite possibly less work than peeling off the roof (which is bound to get wrecked in the process) and piecing in timber on the sides.

 

[Sea Dog]

Can't help thinking it'd be easier to have 3" taken out of your shins. Of course, the waiting list might be an issue... 

[magnetman]

I was advised to have my head cut orf as a way to deal with low headroom boats. 

 

Another approach of course is to put in a mollicroft like you see on showman's wagons and very occasionally also on narrow boats. 

Mollycroft 

 

 

Then get a Lara Croft to do the housework. 

 

 

[BWM]

If you're stripping it out, have a look under the current flooring. Many older boats have untidy ballast, raising the floor beyond the necessary minimum and would be a much easier way to increase headroom by dropping the floor. 

[magnetman]

Just now, BWM said:

If you're stripping it out, have a look under the current flooring. Many older boats have untidy ballast, raising the floor beyond the necessary minimum and would be a much easier way to increase headroom by dropping the floor. 

 

 

I did this on one of my narrow boats. removed the floor and was able to drop the level by using the central keelson (proper boat) and cross members as part of the floor with pieces of scaffold board in the spaces between. So the floor ended up being partly wood and partly metal and gained over an inch of headroom. 

 

 

And of course there is the late Jim Mac's Elizabeth which is an interesting approach. 

 

[Redfox]

2 hours ago, BWM said:

If you're stripping it out, have a look under the current flooring. Many older boats have untidy ballast, raising the floor beyond the necessary minimum and would be a much easier way to increase headroom by dropping the floor. 

Checked that today, no go unfortunately

8 hours ago, Tacet said:

I would not have taken this boat on, as it is too much work for me.  But if I was in you position with a wooden top that needed to be raised (rather than replaced) I would at least consider adding the extra bit on the bottom end of the cabin sides.

 

Run around just above the gunnel with a circular/reciprocating saw, lift the top off in one piece. This removes the scruffy lower edge of the cabin, which is the most likely area for rot.  It will also allow you to get at the steel wood interface where leaks and rust abound.  Weld a new steel upstand to give the extra headroom and reassembly is then the reverse of removal.

 

What it will look like, I'm not sure but same applies to increasing the height at the top.    Quite possibly less work than peeling off the roof (which is bound to get wrecked in the process) and piecing in timber on the sides.

 

That's an interesting idea. I've got the boat yard to give me a ball-park estimate for replacing the entirety with steel. If that's too much then it's back to plan A.

BTW, what do you mean by "upstand"?

[Alan de Enfield]

33 minutes ago, Redfox said:

BTW, what do you mean by "upstand"?

 

Imagine an L shaped piece of metal (say) the short leg is 2" and the long leg is 6"-8"

 

The short leg is attached to the boat hull, the long leg then stands vertically upwards.

 

The cabin is slid over the 'up-stand' and attached.

If the upstand is 3" higher than it was previously you can build a 3" high 'wall' and then drop the cabin back on and it will sit 3" higher than it was before.

 

[Redfox]

2 minutes ago, Alan de Enfield said:

 

Imagine an L shaped piece of metal (say) the short leg is 2" and the long leg is 6"-8"

 

The short leg is attached to the boat hull, the long leg then stands vertically upwards.

 

The cabin is slid over the 'up-stand' and attached.

If the upstand is 3" higher than it was previously you can build a 3" high 'wall' and then drop the cabin back on and it will sit 3" higher than it was before.

 

Ah, gotcha!

[magnetman]

How would one lift the cabin without deforming it? 

 

 

 

 

 

[Alan de Enfield]

2 hours ago, magnetman said:

How would one lift the cabin without deforming it? 

 

 

 

 

 

 

Carefully.

[magnetman]

Very Large Helium Balloons might work. Indoors. 

 

 

[Tony Brooks]

11 minutes ago, magnetman said:

Very Large Helium Balloons might work. Indoors. 

 

 

 

More likely some framing and Acrow props between the baseplate/floor/ballast and the framing.

[magnetman]

Yes. Quite a lot of preparation needed I still think the sides might move inwards.

 

 

The point is if it did buckle or move this could later translate to a leaking cabin.

 

 

 

A Mollycroft roof is quite an interesting approach for a narrow boat because it is narrower than the existing top so will not tend to hit bridges. It can also be added to the top in advance of cutting out the existing parts from inside. 

 

Its a wooden top = trouble unless very well done but I reckon a mollycroft would be more likely to succeed than detaching the entire cabin. 

 

One tends to mostly walk down the middle of a narrow boat depending on layout especially if one is tall (I am 6ft2.314in). 

 

In this case as it is empty the layout could be arranged with things like a cross bathroom so as to keep a central walkway. 

 

A picture of the boat is needed really. 

 

 

Edited October 25, 2023 by magnetman
error

[David Mack]

18 minutes ago, magnetman said:

A Mollycroft roof is quite an interesting approach for a narrow boat because it is narrower than the existing top so will not tend to hit arched bridges. 

FTFY

19 minutes ago, magnetman said:

It can also be added to the top in advance of cutting out the existing parts from inside. 

But as soon as you cut through the existing transverse roof frames I suspect the roof would sag alarmingly. The only way you could add such a roof would be to securely attach some 'top hat' shaped steel frames before you cut the existing roof supports, and that would involve making holes in the existing roof.

The alternative would be to leave the existing roof bearers in place across the central raised section. But that would involve ducking every 2 or 3 feet when you walk along the boat.

[Tacet]

2 hours ago, magnetman said:

How would one lift the cabin without deforming it? 

 

 

 

 

 

Struts could be put across the cabin sides before lifting.  The whole lot would probably keep its shape better than removing the roof alone.

 

I'm not saying it is a good idea, merely it is (perhaps) a better idea than raising just the roof

11 hours ago, Alan de Enfield said:

 

Imagine an L shaped piece of metal (say) the short leg is 2" and the long leg is 6"-8"

 

The short leg is attached to the boat hull, the long leg then stands vertically upwards.

 

The cabin is slid over the 'up-stand' and attached.

If the upstand is 3" higher than it was previously you can build a 3" high 'wall' and then drop the cabin back on and it will sit 3" higher than it was before.

 

Yes - except that you could probably use a flat piece to make the upstand.  It could then be off vertical if you wanted to be posh and maintain any tumblehome.

 

There could/should be an existing upstand but they are vulnerable to rusting