Enlarge the entrance to the kitchen

[Krawk]

Sure, we're not talking about much load. Your board is still of no use, which is why it's inappropriate to advocate this to others who might have significantly more bricks above the door.
Doing things intuitively in your own house is one thing, but it's unnecessary to tell others to do wrong.

 

[RoughChuck]

What works is not wrong. A board sufficiently serves the purpose in this case, there isn’t more tensile strength in untwisted iron halfway in use. TS doesn’t have more above the door, the advice was based on his conditions. Such arches or openings with loads from that time always have a concrete beam. But now I’m dropping this, no matter what’s written

 

[Krawk]

What works is not wrong. A board serves a sufficient function in this case,

Your board is of no use. Your arch is clearly managing with existing arch action in the stone and cohesion in the mortar. However, how stable this construction is, is unclear.

there is no more tensile strength in untamed iron half in mortar.

Not more strength in the fracture phase perhaps, but a completely different stiffness.

TS has nothing more above the door, the tip was based on his conditions.

Your wall and TS are still not the same. They may be similar, but you don't know more than that.
Still inappropriate. (In your case, as well as TS)

Such arches or openings with loads from that time always have a concrete beam.

All properly executed non-arched walls over openings have a supporting beam construction.
(Yes, an arch can be straight at the bottom)

But now I'm dropping this, whatever is written

Please write more. But first try to calculate a masonry beam with wooden tension reinforcement with respect to deformation over time.

 

[RoughChuck]

Ok you got me I must respond
First, I just want to clearly say that I'm not so damn stupid to think that wood is a construction reinforcement in that sense, so calculating it is out of the question.q(;^p
Iron (often not ribbed iron as mentioned) placed like that doesn't hold the stones; under any load, the stones can "slide" on the iron. For the reinforcement to work, it must be embedded on top of the bottom layer, and if it's not ribbed iron, it should be bent at the ends so they can be held between the stone a bit "beside/outside" the arch. It seems like you have that down pat, so my conclusion is you don't often find yourself in this situation for real? You can remove iron placed like that simply by making space for the fingers in the middle with a knife and then just pulling downward so they slide out on the sides too. Under a load, they would give way immediately.
I know that "my board" with screws has limited effect but does at least as much good as those irons, and if it's nothing, then we're back to square one—it can be removed.
I firmly claim that the board is useful because the tensile forces at the bottom are counteracted, and the wall holds up much better against lateral loads. I might annoy you by saying that I also set side jambs of about 20mm material so they hold the stones together too if someone misses the hole on the way through

 

[Krawk]

Actually don't understand what you're trying to say now?
It's good that you have realized the pointlessness of your board.
Then you might understand why I react when you recommend that solution to others?
A frame around the opening is of course not wrong. But it does not serve the function you claim.

Of course, smooth irons should be equipped with an end bend. This would also have been needed with a cam iron at these distances since the anchorage lengths are far from being met. The fact that this is not the case in your house is unfortunate; someone probably thought it was too troublesome to arrange this, which is why the iron is now, as you've noted, ineffective.
Note, however, that even the shift with brick stones is a reinforcement as these withstand greater pressure than the lightweight concrete. Hence my earlier reference to it as a "brick beam."

 

[RoughChuck]

No, it actually doesn’t seem like you even want to understand , "brädan" is far from pointless, it (with the screws naturally) counteracts tensile forces even if it can’t compete with properly executed reinforcement.
But because I have noticed from experience in many places (not just my house) how it IS done and not how it maybe SHOULD be done, I feel I can, in good conscience, suggest the idea in the "right" situation.
Take care, Krawk

 

[Krawk]

No, it doesn't actually seem like you even want to understand , the "board" is far from useless; it (with the screws, of course) counteracts tensile forces even though it cannot in any way compete with properly executed reinforcement. But since, from experience in many places (not just my house, that is), I've noticed how it IS done and not how it maybe SHOULD be done, I feel that I can in good conscience recommend the idea in the "right" case. Take care Krawk

Indeed. I've understood that you believe your board works. However, I cannot understand how the fact that the wall obviously manages without tensile reinforcement would prove this in any way. Apples and Oranges.