Loose brick arch above sash window

[Saving Laurel]

Hi All,

New to posting but regularly visit to see what’s going on and inspiration. We’re currently repainting our external joinery using Linseed Oil paint. In the process of raking out old cement mix around the windows I noticed that three bricks are loose above the window. Everything else feels solid/stable - but I don’t want these working loose and/or falling out.

Photo attached of the bricks in question can update with a bigger one when I’m up the scaffolding later - wisdom greatly recieved

Thanks!

 

[Stevers]

This is a job that I've just had to do to make good a fireplace arch in my basement. You'll need to make a form that fits the opening. Once the support is wedged tight from underneath, and each sound brick is wedged in the correct place, you will be able to carefully remove and replace the dropped bricks in the correct position using NHL mortar. The replaced bricks will need to be packed to align them correctly.


This arch was in a very poor state and has had the defective bricks replaced with new ones. The missing bricks in this picture have now been replaced, both sides rebuilt and the centring safely removed, and the arch is now completely sound again. Restoring the arch has completely stabilised the previously wobbly stonework above.

 

[Cubist]

Hi There,
Much/all of the strength of such arches is achieved mechanically by transferring the compressive forces toward the sides and then down to the ground. Some movement from thermal cycling will always have some impact and normally that will affect the mortars bond to the bricks and over time cracks will begin to open up. Theres a good chance you've caught this in time as there are clear gaps between the window frame and the brickwork. The best approach in my view would be to provide some additional temporary support, perhaps using a wooden form, to the affected bricks while you rout out above 20mm of the mortar and re-point with a compatible lime based mortar. If you can, be sure to do the same on the inside if the bricks are exposed there too.

I was about to add that Stevers has some useful knowledge in this area but he beat me to it. Ho hum.
Good luck.

 

[Saving Laurel]

Thanks both - much appreciated. I happen to have some Mike Wye lime mortar in the garage so that’s half the job. I’ll see if I can beg/steal/borrow an acrow and fashion some kind of support. Can the patching be done in situ if the bricks are mechanically wedged and sufficient failed mortar can be removed and replaced (aesthetics aside)

The bricks aren’t exposed internally but as there is a gap, is there merit in stuffing some mortar between the back of the bricks and the top of the sash frame/whatever else is up there. Intending to pack out the gap with oakum and traditional/lime caulk.

Thanks again

 

[Stevers]

Leaving them in place and chasing out as much mortar as possible is worth trying. If full length bricks they may of course be hard to remove. The key to doing them in place will be to remove as much mortar as possible, wedge them in the right place against the support, wet well, and pack the fresh mortar in nice and tight as it starts to set. All this assumes that the arch hasn't failed due to subsidence or other movement of course, in which case, whatever has caused that will need looking at too.

The two props under my arch support were loaded with folding timber wedges that I squeezed together with a G Clamp to get plenty of pressure on them.

 

[Saving Laurel]

Thanks Stevers, really helpful points. We moved in last July; there was historic movement but nothing recent and we had a full survey carried out. We inherited quite a few issues with the old girl - gradually getting round to fixing them and discovering more. Will get some timber tomorrow and try to fashion a similar device - think if located two props!

 

[stuart45]

I built a decorative arch when I did the kitchen. It was in the old back door opening, so there was a lintel in place. Getting the bricks under the lintel was the hardest bit, but luckily my wife wanted a rustic look.

 

[Cubist]

The bricks aren’t exposed internally but as there is a gap, is there merit in stuffing some mortar between the back of the bricks and the top of the sash frame/whatever else is up there. Intending to pack out the gap with oakum and traditional/lime caulk.

I would not advise using oakum, the oil will bleed into the surrounding materials and paint and it can be difficult to get a uniform finish. Packing the gap with mortar between the window frame and the brickwork, while it won't produce unsightly stains will have little benefit and you may find that there are quite large cavities behind the woodwork. In your place I would simply use a caulking cotton, braided to make a thicker rope if necessary, that is packed into the joint with the edge of an old bolster chisel or similar. Leave a cavity of 3-5mm between the outer face of the window frame and the adjoining brickwork to accept a lime filler for the final finish.

 

[Saving Laurel]

I would not advise using oakum, the oil will bleed into the surrounding materials and paint and it can be difficult to get a uniform finish. Packing the gap with mortar between the window frame and the brickwork, while it won't produce unsightly stains will have little benefit and you may find that there are quite large cavities behind the woodwork. In your place I would simply use a caulking cotton, braided to make a thicker rope if necessary, that is packed into the joint with the edge of an old bolster chisel or similar. Leave a cavity of 3-5mm between the outer face of the window frame and the adjoining brickwork to accept a lime filler for the final finish.

Thanks Cubist - there are a few deeper pockets so will use this approach for that.