How to rebuild this- decorative arched section above window

[Lower]

We're in the process of having some 1980's double glazing replaced in our 1920s house. Unfortunately, the decorative arched feature above the landing window that used to look like this:

Now looks like this

Annoyingly, the whole section appears to have been supported by the window below and when the window was removed, the whole section fell apart.

How should i rebuild this? It was originally constructed from thin brick and clay roof tile slivers, bonded together with lime mortar into some wood laths in the same way that lath and plaster holds itself together. But the laths weren't attached to anything so the whole thing was held in place by gravity and friction. Probably quite lucky it hadn't fallen out anyway!

I can put a piece of steel in above the window to support the rebuilt feature, but not sure how to reconstruct it and tie it in to the original arch.

 

[ree]

OP,
The ceiling joists are resting on some kind of "lintel" - which in turn is sitting on perhaps a steel angle iron?
Is that the case? What material is the lintel?
Using hardboard you can make a template of the arched opening.
You can then use the template for however you decide to re-build.

 

[Harry Bloomfield]

I can put a piece of steel in above the window to support the rebuilt feature, but not sure how to reconstruct it and tie it in to the original arch.

It looks as if, you may have a concrete lintel, resting on the inner wall leaf, providing support for the ceiling timbers. The arch looks sound, so no risk there. Your only problem is filling in that arch, and that is a matter of how much you want to spend upon it. A made to measure normal window frame and (dummy) window, might look best, but would be the most expensive solution - as well as the most satisfactory solution.

Other than that, you could price up with a local joinery company, to make up a simple frame, if you made up a basic template from ply, etc. You could then fix that in place, then infill the face, with cheap UPVC, tongued and grooved.

 

[Lower]

There is a wooden lintel that bridges the gap that supports the ceiling timbers. The old infill was some half depth bricks that were supported by the window frame with edge on slips of roof tiles to create the look that was there before. I'd like to recreate the original appearance, or something similar.

Current thinking is that i put a 10mm x 150mm deep steel plate across the gap, partially supported by the wooden lintel, to take the load of the infill, instead of it resting on the window frame.

I'm then thinking that i can cut a piece of WBP ply to the same profile as the arch, and use that as a backer board to attach similar slips of roof tile to, bonding them on using modern cement based tile adhesive.

 

[Harry Bloomfield]

I'm then thinking that i can cut a piece of WBP ply to the same profile as the arch, and use that as a backer board to attach similar slips of roof tile to, bonding them on using modern cement based tile adhesive.

I would not trust the adhesive!

 

[Scally-Ho]

I'm not struck with any of the OP's idea. Stud the aperture out properly and then affix felted ply before battening out ready for tiles to be fixed properly. If water is not shed in the correct manner, rot will set in after a short time.

 

[stuart45]

The infill under an arch is known as a Tympanum. Normally you do a piece of decorative brickwork, like a herring bone panel with rubbed bricks. I wouldn't be rebuilding it with a load of random rubble.