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[SableSprings]

OK. Mortar. I *think* I am supposed to use 20 sand:4 cement:5 hydrated lime. Does that sound right?

Here's the most common types of mortar used here...

6:1:1 (sand, lime, cement) is a standard (Type N) outside and below grade mortar with no high heat situations.

9:1:2 (sand, lime, cement) is a standard (Type S) that provides a higher compression and structural elasticity factor (high winds, and minor ground shifts.

3:1:1:1 (sand, lime, fire clay, cement) - the home brew mortar used as a refractory (high heat) mortar by most Forno Bravo forum builders.

Not quite sure what the 20:5:4 (sand, lime, cement) formula does for you. I'd recommend using the 3:1:1:1 home brew mortar formula for your inner arch (and finishing the rest of the dome) since it's a proven winner for this application. If you find out or have information on the 20:5:4 mix, I'd like to see it...thanks in advance


Looking at your arch brick pictures, you will have a slight problem with the current brick set. The reason is that you will be adding a layer of mortar between each set of bricks and that means the arch will be larger than the dry layout. I'd get some cardboard and place a piece between each brick set, about halfway down, to see what happens. I suspect the easiest fix will probably be to cut the end arch bricks (both left and right) thinner to compensate for the mortar.

Hope this makes sense. I basically did the same thing on my arch...so proud to have them all fit so beautifully together when cut, then shocked to find they didn't fit even close when I started mortaring them in place

[Amusinglisa]

Thank you, Mike! I think I will drop that mold a bit and re-lay the bricks with the cardboard, as you suggested before I get mixing the correct brew. I don't know where the other numbers came from, but I think that may have been what the "friend" was using. Ugh.

[UtahBeehiver]

Mike has given you some great advise. I second the need to add fire clay to any heat exposed brick joints. HC Muddox mortar clay is a California product and very inexpensive. You will need to go to a masonry supplier to get it, most likely not a big box store item.

[Amusinglisa]

I have a local landscape supply that has everything but the lime, which I have to mail order (eeeek).

[UtahBeehiver]

You should be able to find type n or type s lime at any big box store, HD, Lowes, Ace

[Gulf]

Also check out your local farm supply stores.

[SableSprings]

Also check out your local farm supply stores.

Be careful and check that you are getting hydrated lime - Calcium hydroxide (not agricultural lime - Calcium carbonate). Crushed lime (agricultural) is often used as a soil enhancer and will not work in making mortar or concrete. Check to see if there is a local builder's supply that is used by masons in your area. Check the yellow pages or as Russell said in post 20 above, the big box stores may have it or be able to order it for you.

[Amusinglisa]

I cannot get lime here in Claifornia. Trying to find out why. Ordered from Amazon -- type S. Is that OK?

[Gulf]

Type-S Hydrated lime is perfect. The farm supply stores down here stock it for for flea and tick control.

[UtahBeehiver]

I don't know where you are looking but Home Depot in Placerville, near you, has type S lime. Probably worth the drive over there versa mail ordering

[Amusinglisa]

No, it doesn't and hasn't for a full year. Every time I check, it is Unavailable at Placerville
Check Nearby Stores and "This item is not available in any stores within 100 miles of 95667."

[UtahBeehiver]

Then something is screwy. I just looked and here is a screen shot of the store stock.

[Amusinglisa]

Holey socks!!

I'll just call the stores. Maybe I am misspelling or something. Anyway, I have to bags here, so dlrymixed now and adding water in the morning to get the inner arch set. Here we go!!

[Amusinglisa]

D'oh! Must have specified the wrong brand

[Amusinglisa]

OK -- I got my gumption up and got my homebrew mix all nice and like organic peanut butter. We have some oddly cut bricks that we used as best we can - the plan is to do the outside with a layer of kiln blanket and stucco, so I worried more about structure and less about getting the outer surface all perfectly even. Here is the pictographic story so far: