32" build in Calgary, AB - pompeii neapolitan

[david s]

Although there have been many successful brick galleries built and traditionally it is the method used, a cast refractory or stainless gallery have more advantages, both in reducing thermal mass, structural integrity and being better to adapt to curves easily.

Brick units are not ideal because they have two big drawbacks. Firstly it adds a lot of thermal mass in an area where you don’t really need or want it. Secondly, brick units introduce instability. because of the many mortar joints, introducing weak points from thermal expansion and contraction.
Also an inverted arch as in the second drawing is inviting expansion rather than compression.
Anchor plates usually call for drilling holes and using fixings, both of which can lead to areas where cracks develop. Using an alternative method to fit or omit one is worth considering.

[IH123]

Although there have been many successful brick galleries built and traditionally it is the method used, a cast refractory or stainless gallery have more advantages, both in reducing thermal mass, structural integrity and being better to adapt to curves easily.

Brick units are not ideal because they have two big drawbacks. Firstly it adds a lot of thermal mass in an area where you don’t really need or want it. Secondly, brick units introduce instability. because of the many mortar joints, introducing weak points from thermal expansion and contraction.
Also an inverted arch as in the second drawing is inviting expansion rather than compression.
Anchor plates usually call for drilling holes and using fixings, both of which can lead to areas where cracks develop. Using an alternative method to fit or omit one is worth considering.

Thanks for the reply. however , I already purchased additional mortar and bricks to build the arch. I am avoiding castable refractory because casting isn't always better. A cast refractory must be allowed to dry and cure properly and I have no experience in that- thermal expansion still has to be accommodated with rigid cast tied tightly to refractory bricks tightly can crack too. I am looking to choose a brick arch. I am going for now, unless someone tells me about a better brick arch design, with the inverted arch because I am planning to create a concrete buttress for the arch (regular concrete not refractory concrete) and separate the arch from the concrete buttress using leftover CaSi and/or Ceramic Fibre boards - I believe having a rebar reinforced concrete pillar buttress will create a very well solid support for the chimney and the full archway especially its not connected to dome , it will allow me to go higher .

[IH123]

I today completed the dome, and the inner arch was already complete. the dome ended up about 13.5" high instead of 14 1/8", I did not use trammel for top courses and likely mortar was thicker than planned and brick cuts might have been not exact. The dome top stone brick wasn't like you expect like a polygon on or anything like it,I jut used regular dome brick cuts and fit them in anyway that reduces mortar thickness to be between 3mm-9mm (my mortar specification/ requirement) - ended up a dump of bricks however they are tapered so they got locked without mortar (however mortar was used). here are the pictures:

[IH123]

and I believe I will proceed with the following for the remaining arches. as originally planned: inverted arch for flue gallery (6-6 1/4" deep) and segmented arch for mouth arch (~3" deep) however will as planned have a buttress as shown below: