Fallen Arch

[nick2013]

Suggestions ? I think the heat did this last year, I'm just in the process of rebuilding it, the archway was
the hardest bit...

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[spinal]

Apr 6, 2014 13:16:19 GMT nick2013 said:

Suggestions ? I think the heat did this last year, I'm just in the process of rebuilding it, the archway was
the hardest bit...

In my humble opinion, the sides of your arch aren't supported. An arch coverts vertical forces (gravity) into horizontal forces. Thus the arch pushes its sides outwards. In my opinion, the sides of your arch, not being supported, moved just enough to allow the arch to collapse.



I would take the mortar off the bricks, rebuild the arch - but somehow stop the sides of the arch pushing outwards... that could be buttresses, or somehow tying them into the dome...

M.

[nick2013]

Thanks for that, I'll keep that in mind when I rebuild it.

[tonyb]

I think you've been unlucky, I can't remember anyone reporting a similar occurrence but I could have missed it.

Most of us build arches using whole bricks with wedge shaped mortar joints, which i think is what you've done also, (rather than the wedge shaped bricks in the diagram), so there's a greater possibility that if you get some sideways movement then its more likely that a brick could become detached from the mortar on both sides and actually fall through the gap which I think is what has happened in your case. Again I think this is more likely to occur if the keystone is a full brick rather than shaped as in the picture. I don't think a buttress is normally required particularly as you have a lightweight flue stack but would help prevent sideways movement.

[albacore]

I had the same issue; it is down to unsupported side walls. Unfortunately this isn't well publicised and, like me, you found out the hard way!
The neatest way to fix it is to tie the side walls into the dome render as you rebuild the arch. I think buttresses might look clumsy.
Have a look at my build thread here for two methods I used.

[bookemdanno]

If it didn't happen when hot, its more likely to be freeze thaw.
Water enters a crack, freezes, expands, and blows apart the joint further.

A real shame, but a real chance of damage to an oven.
The top section of an arch is very susceptible to a heat induced "fissure" which the frosts then capitalise on.

Voissoirs, or tapered bricks can help in this situation as they'll nearly always stay in place.
Even when all are loose. A fully hemispherical arch could also be better, as the forces are equal and directed downwards i believe.

Good luck with the repair...just think..its a chance to work on the oven again!