Double arch builder's opening in fireplace - can I remove one?

3 Sep 2017
Reaction score
United Kingdom
Hi there,

I'm currently opening up the fireplace in our 1890s terrace to put in a reclaimed old cast iron fireplace. All well and good, but the cast iron insert is too tall to fit in the builders opening as it stands. Even if I were to remove the 3" hearth, it'd still be a shade too tall.

The fireplace is supported by a brick arch consisting of two rows of half-size bricks - see image. If I were to remove the lower arch, the insert would fit.


The alternative seems to remove the arch entirely and replace it with a concrete lintel at the level of the upper arch.

Grateful for some advice as to whether I can safely remove the lower arch and rely on the upper arch to support the masonry above, or whether it would be better to replace the arch altogether with a proper lintel.

Also, I need to remove the existing fire back (in picture) and reset it deeper into the recess. What's the safest way of unseating it without causing it damage?




  • 1B6E1B63-F565-4D9A-9C2F-6C4E1D7D0B4B.JPG
    254.5 KB · Views: 281
Sponsored Links
Personally (and having exposed the same archway in our house recently), I would install a lintel. We were lucky and were able to keep the archway without touching it, so there were no concerns over safety.

With that archway, the strength is found at the sides where the bricks push against either side of the opening so removing just one row would surely compromise strength. I would be safe and put a solid lintel in - at least they you know it's all safe and sound :)

As for your fire back, it's very hard to keep these complete when removing as the material is so brittle. I found chiseling at the bottom very slowly and working your way around removes it from the hearth it is sitting on. The hearth is easier to move.
Thanks very much for the excellent advice. I'll go with a new lintel. I was lucky and managed to unseat the fireback by rocking it back and forth, so got it out intact.
Thanks very much for the excellent advice. I'll go with a new lintel. I was lucky and managed to unseat the fireback by rocking it back and forth, so got it out intact.

No problem. If the fireplace had been short enough to fit, I would absolutely have said keep the arch, but by removing that bottom layer the arch would lose some of its structural properties.

Good news on the fire back too - mine felt like it had been bolted down...
Sponsored Links
What sot of finish do you intend to have on the the chimney, and why do you want to reseat the firebrick. If you are going to replaster the chimney, then take out both rows of soldier bricks, and put in the concrete lintel, but if you are going to take off the plaster, and have a bare chimney, then take out both soldier courses, remove a couple more courses of bricks, make up an arched former, and rebuild a new arched soldier course. A fireplace is only about 15% efficient, but a multifuel stove of over 75%. Plus the fireplace draws so much cold air into the room, that you're hot in front of you, and cold behind.
Hello Doggit,

The firebrick needs to be reseated because we're putting in a tile insert that sits further into the fireplace. Agree that woodburners are much better for heating, and we'll probably get one for that purpose in another room, but there's also something nice about an open fire once in a while too!

DIYnot Local

Staff member

If you need to find a tradesperson to get your job done, please try our local search below, or if you are doing it yourself you can find suppliers local to you.

Select the supplier or trade you require, enter your location to begin your search.

Are you a trade or supplier? You can create your listing free at DIYnot Local