Hi can anyone tell me how to build a welsh arch, my brother has to find out for his construction homework and I can't find nothing on the internet about it.

I can tell you how to build an arch, but I'm unsure what a welsh arch is. Can you give more detail?

It is an arch in wales, uk apparently the bricks go a certain way but I'm not quite sure myself, if you can't answer it no problem thanks fro trying.

I've looked myself to see and I'm running into the same problem sorry I couldn't help

I believe that a Welsh arch is an arch made with three masonry units. The two outer units cantilever over the window or door jamb and are angle cut symmetrically to receive the keystone unit. The bottom of the arch is perfectly straight with no curve or "arch". The strength comes from the force of pressure from the keystone pushing against the two outer units.

We have welsh arches on our 1930's house. Our builders are going to replicate it for the garage we are building.
The arch is made up of a different brick to the house i.e soft reds. The bricks are standing up and angled from one side to the other like a v above a window or door in the lintle. Straight at the bottom and straight at the top. The bricks have to be cut at an angle one and a half bricks high alternating each one. In the middle are tiles thick at the top going smaller at the bottom to fill the v, usually done with a different morter colour. Looks very nice when done. Hope this helps. Helen

A Welsh Arch is an arch made of three bricks that go over a single pipe in the ground instead of using a lintel bricks at each end of the void are corble and cut at 45% at the end that is corbled the key brick is cut at 45% both ends and the placed in the gap that's over the pipe
That's what is called a welsh arch its only three bricks

As the old bricklayer said, "That's why it is called a welsh arch its only three bricks"... see image below: