Hi Chris,
As several people have already commented, 1:12 is the most common scale for dolls houses and associated accessories. You would need to get your plans doubled in size to match that scale. Alternatively, there is a more limited range of dolls house material in 1:24 scale which would match your existing plans.
Deans Marine do a 1:12 scale narrowboat hull which is about 43 inches long and can be made into a very detailed model which is not too difficult to launch, store or transport. I used it as the basis for my model Walbut Dream which was based on several narrow boats on which we have had family holdays.

The model was featured in the August 2012 edition of Model Boats magazine and there are some other photos on the forum here **LINK**