Attach interior walls directly to the steel

[Noviceboata]

Hi guys,

Has anybody attached the plywood, mdf or any material directly to the steel steel structure on the interior of a narrowboat after installing insulation such as polyurethane? (No stud wall) Just trying to save a bit of space for the interior. I guess that is how it is done for the ceiling

Edited October 29, 2022 by Noviceboata
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[Higgs]

10 minutes ago, Noviceboata said:

Hi guys,

Has anybody attached the plywood, mdf or any material directly to the steel steel structure on the interior of a narrowboat after installing insulation such as polyurethane? (No stud wall) Just trying to save a bit of space for the interior. I guess that is how it is done for the ceiling

 

If you have insulation, you will need battening of some sort to extend beyond the space the insulation occupies.  available to attach wood panelling. If you attach the panelling to the steel, you will suffer from condensation. You need to separate the cold steel from the warm interior. Without insulation, the cold is transferred to the interior, and warm air meeting a cold surface produces condensation.  

Edited October 29, 2022 by Higgs

[Noviceboata]

1 minute ago, Higgs said:

 

If you have insulation, you will need battening of some sort to extend beyond the space the insulation occupies.  available to attach wood panelling. If you attach the panelling to the steel, you will suffer from condensation. 

Thanks for that. What would be the minimum thickness of the wood? Just enough to cover the insulation that is sticking out?

[Higgs]

10 minutes ago, Noviceboata said:

Thanks for that. What would be the minimum thickness of the wood? Just enough to cover the insulation that is sticking out?

 

Wood is structurally required to meet the requirements intended. Heavier can be used on the sides, and lighter on the ceilings. Battening needs to be stout enough and well secured to perform a supportive roll. You're not building a tank, but some thought needs to be given on rigidity and strength for purpose. So, if you use thin ply and too few battens, it will end up rippling.

 

 

Edited October 29, 2022 by Higgs

[Noviceboata]

4 minutes ago, Higgs said:

 

Wood is structurally required to meet the requirements intended. Heavier can be used on the sides, and lighter on the ceilings. Battening needs to be stout enough and well secured to perform a supportive roll. You're not building a tank, but some thought needs to be given on rigidity and strength for purpose. 

 

 

 

Thankyou for the info!

[Rose Narrowboats]

Assuming you're doing this to live on, and the budget doesn't run to sprayfoam, then use 2" polystyrene on the deck head (done in two 1" layers to it will bend to the profile of the deckhead), minmum 1" on the cabinsides (preferably 2") and 2" below gunwhale. Cabin framing looks like 1" box, so 1" battens will do the job. Any less and the timber will soon start to go black (from condensation) where it is close to the box section.

 

With the fraiming you have, run the battens fore and aft on the deckhead, cabin side and hullside- this minimises contact with the steel and also supports the ply better.

 

9mm ply for the deck head, 9 or 12mm for the cabin sides, 12mm below the gunwales. Personally I'd use T&G pine above the gunwhale - it's a lighter material (so the boat will be less roly) and you can go a bit thicker so it's stronger and also a slightly better insulator than ply. If you use T&G then thebattens need to be done accross the boat, not fore and aft

 

Do not insulate with rockwool (except around the flue collar). Do not use MDF for lots of reasons.

 

Do put thin polystyrene tape on all the between the battens and the steelwork. Do fit the polystyrene nice and tightly, and fill in all the little gaps - it makes a difference.

Edited October 29, 2022 by Rose Narrowboats

[David Mack]

If you are getting the boat sprayfoamed, then fit the battens first, to the face of those steel angles and box sections, then the sprayfoam will fill behind them. After spraying you will need to cut the excess foam back to flush with the battens so you can then fix the lining.

If you are using celotex/kingspan boarding you could use two layers, one behind the battens and one between the battens to achieve the same effect. Ensure 100% coverage and tape all joints with the proper tape to provide a vapour barrier to stop moisture getting to the inside face of the shell.

[BEngo]

If you are not using spray foam insulation you need to add a layer between the insulation and the plywood, to form a continuous  vapour proof barrier.  This stops the warm, moisture laden, air from the inside of the boat getting to the cold outside steel and condensing.  It will get through the smallest gap, so be conscientious.

 

If you use kingspan type insulation, then tape every join between two pieces of insulation  using aluminium tape.  If using polystyrene sheets, cover them with builders plastic membrane, taping the joins as above.

 

Beware of the effects of PVC cable insulation on polystyrene foam sheet.  The plasticiser in the cable sheath can eat into the foam and the cable becomes much less flexible, but sits in a groove in the polystyrene.

 

Spray foam in tins (from builders merchants, screwfix, toolstation etc.)  is very useful for filling small holes and gaps at joins.  The gun grades are easiest to use.

 

N

[dmr]

59 minutes ago, Rose Narrowboats said:

Assuming you're doing this to live on, and the budget doesn't run to sprayfoam, then use 2" polystyrene on the deck head (done in two 1" layers to it will bend to the profile of the deckhead), minmum 1" on the cabinsides (preferably 2") and 2" below gunwhale. Cabin framing looks like 1" box, so 1" battens will do the job. Any less and the timber will soon start to go black (from condensation) where it is close to the box section.

 

With the fraiming you have, run the battens fore and aft on the deckhead, cabin side and hullside- this minimises contact with the steel and also supports the ply better.

 

9mm ply for the deck head, 9 or 12mm for the cabin sides, 12mm below the gunwales. Personally I'd use T&G pine above the gunwhale - it's a lighter material (so the boat will be less roly) and you can go a bit thicker so it's stronger and also a slightly better insulator than ply. If you use T&G then thebattens need to be done accross the boat, not fore and aft

 

Do not insulate with rockwool (except around the flue collar). Do not use MDF for lots of reasons.

 

Do put thin polystyrene tape on all the between the battens and the steelwork. Do fit the polystyrene nice and tightly, and fill in all the little gaps - it makes a difference.

 

Do you mean the thin expanded polystyrene "tape" just a couple of mm thick? Our boat was done with this in places, such as over the steel framing and under the 'gunnels' . It has failed. Because expanded poly is not fully airtight the stuff becomes water logged in winter so its worse than useless as it retains water against the steel until it falls off.  The thicker (inch or so) stuff used as the main insulation has done ok, boat is over 20 now and its still in reasonable condition. Extruded poly is  better than expanded poly though there is a question aboit its fire performance, but "proper" insulation board would have been much much better.