Currently building a new chimney above the roof as the old one has failed due to frost damage. Planning to top it with a new cast chimney crown. Several people I’ve spoken to suggest "extending" the crown 45mm outside the brick and casting it with a drip edge. The 45mm seems to come from the fact that most people build the form using regular construction studs.
I think 45mm would look strange on my chimney, is there any major disadvantage to reducing it to a 35mm overhang? Still with a triangular molding in the form to get a drip edge.
I think 45mm would look strange on my chimney, is there any major disadvantage to reducing it to a 35mm overhang? Still with a triangular molding in the form to get a drip edge.
How much it should protrude is up to you. However, it is positioned quite high up and a 10 mm difference might not be very noticeable. Our krona probably sticks out about 90 mm, but it is 11 m up, so it doesn't seem like much when you look up. I've never seen a droppnäsa on kronors. It's probably not wrong, but more important is that the top is convex so that water can run off.
I'm quite picky with the details and odd proportions are often visible even from a distance. I don't just want a "slab" on the chimney. Hence the question. I'll probably go with a 35mm overhang. Just need to rebuild the darn thing first ;-)
My chimney crown sticks out about 20 mm beyond the brick, the chimney is 400x1500 in cross-section. I don't know what's appropriate, but I'm thinking of making a new one that's the same as the old one.
FireMaster provides good instructions here:
http://www.byggahus.se/forum/biobransle/59426-tillverka-skorstenskrona.html
http://www.byggahus.se/forum/biobransle/59426-tillverka-skorstenskrona.html