Cutting bricks to fit dome...

[BrritSki]

I've had a look round the forum and tried search, but can't find any references to this idea - there's a mention of tapering bricks in the plans pdf, but nothing in the appendix as suggested on page 31...

Does it make sense to cut your firebricks to fit the dome ?
i.e if when you lay out the bricks in the dome shape (cf page 9 of plans pdf) you see that there are e.g. 11 bricks between the first soldier-brick course and the final vertical brick, that means there are 12 gaps and a 7.5 degree angle between them all. If you then cut the bricks in half at this angle rather than at a right angle you can lay each course without the use of shims.
This means that there is little mortar (if any) used in the horizontal joints - is this a good or bad thing ?

A further refinement would be to also cut one of the "vertical" edges of each brick at the appropriate angle (changes for each course I think) so that they all fit together - this would use more bricks in each course, but less mortar and might look strange from the inside with a sort of spiral effect to the brick work.

Has anyone tried this or is the idea completely stupid ?

TIA Roger

[Les]

Roger - I'm trying to go this route. And you are correct, it does require a LOT more cuts. The only mortar that I am using is on the back of the bricks to maintain the vertical angle. If you go to my link, you can see the little progress I have made so far. The weather is getting better so I should be able to get back to work on it soon.


Les...

[BrritSki]

Wow, you are much more ambitious than I was suggesting with every brick cut perfectly to shape and no mortar needed hardly - do you have Inca blood in your veins ?

My initial idea was just to cut each brick in half at an angle, so no extra cuts, but they're all a tiny bit longer.

Second idea was just to cut a slice off each side so they fit at the "front" (i.e. inside the dome).

Your method of perfect cuts does look BEAUTIFUL though....

Ciao Roger

[dmun]

This is an idea i came up with a year ago, and I don't think anyone has done it yet, I call it the cut-every-other-brick-dome.



It cuts mortar use in half, and every brick is a wedge, which may increase dome strength.

Unless you have tapered firebricks, I don't think a cut-every-brick to perfect fit is practical.

[BrritSki]

Interesting, I agree that getting a perfect taper is perhaps impractical for most of us, but I think my idea of cutting bricks in half at an angle might be helpful, and yours is 1 step further along than that...

Ciao Roger

[BrritSki]

Thinking about this some more, I guess I'm assuming that the half-bricks will be set on their cut face, but that won't work for some shapes of brick, only for the ones that are roughly square cubes when cut.
I've only worked with normal British house-bricks before, what are the dimensions of fire-bricks and will my idea work at all ???

Ciao Roger

[dmun]

I got a bricklaying tool from Ireland, which I assume has the same standards as the UK. It was a perfect fit to US house bricks. Firebricks, I don't know.

The idea I sketched above should work with any brick. The two ends of the brick are cut off with a square inside face on the 7 degree angle, needed to form the vertical course of the dome. On the first layer, the piece left over in the center of the brick is laid horizontally to form the outside circle. These are good as cut for the first layer or two of the dome, then they need to be trimmed at an angle as the courses tilt in.

[Les]

Originally Posted by dmun

Unless you have tapered firebricks, I don't think a cut-every-brick to perfect fit is practical.

I don't think I have ever been accused of that.

Les...

[Frances]

Les, it'll be good to see you at work on your dome again! I've been looking forward to that all winter...

[RTflorida]

Les, I guess you and I are in the minority (although you have gone to the EXTREME extreme with your mortarless dome). I merely cut every brick to stay within the mortars recommedation for joint thickness (1/16"-1/8" side to side and no more than 1/4" between courses on the outside).
I think that if you are going with an igloo style you should do anything and everthing to avoid potential cracking, so not exceeding the recommended joint thickness seemed like a good idea at the time...don't know if that is the reason for my minimal cracking (a few hairline cracks in the mortal of my mosaic tile - nothing on the inside). VERY time consuming, but worth it to me.

RT