16c Fireplace - delicate renovation

[surreysteve]

Thanks for reply. The metal band is actually pretty sturdy although I will keep a watching brief.

...just a quick note. They certainly aren't pozi's - well fixed 4" sleeve anchors.

Steve

 

[Penners]

that strip needs to have an upstand - like a piece of angle iron - welded to it so as to make a T shape.

I agree with 88v8. That flat piece of steel has very little resistance to flexion.

In order to provide much more rigidity, I would have had a blacksmith make the strap out of angle (L-shaped) with the horizontal face as near the full depth of the arch bricks as possible, and the vertical face hidden on the inside of the arch. The ends would have been mortared into the cheeks of the stack.

To fill the irregular voids between the underside of the arch and the flat of the angle, I would do as suggested by Zebra above - use lime mortar for the slight gaps, filled with slips such as pieces of tile in the larger gaps.

 

[billybuntus]

Have you thought about rebuilding it.

Now that you've removed the cement you can see just how far its gone.

I would find some matching brick (something close) take that full section out including the arch and rebuild it. I'd make it into an inglenook and reduce the arch side. The lime will knock off your existing bricks easily.

It will also add support to the floor above (not that it probably needs it looking at the size of those beams. But every little helps.

It's far from a piece to conserve in my opinion. It adds nothing but shows how bad workmanship can be. You'll ensure it will still here in 100+ years if you commit to it which is a far better approach than trying to extend its life by 10 years.

 

[Keithj]

The way those bricks sag, and the wavy line they trace, isn't exactly quality work. I would be suspicious that it wasn't like that until relatively recently. It looks as if gaps immediately under the beam have been filled in.

We had a similar mess in one of the apexes of the church roof. We decided (with permission) to have it dismantled and rebuilt. The builder doing the work told me afterwards that he found evidence of at least three attempts to fix it in relatively recent times (because they used cement rather than lime). He also found the cause of the problem when he removed the bricks - a "fix" was never going to work.

I would be inclined to ask an expert (the CO if you have one, or one of the serious professionals otherwise) for advice. If you're going to fix it, do it right.

 

[Penners]

I'm afraid I agree with the above remarks. I really don't feel that the repair as carried out is a reliable long-term solution to the problem.

If it were my fireplace I would do as has been suggested - dismantle the face of the chimney breast completely, below the crossbeam, and recover as many of the bricks as possible. I would then install an iron arch as I described above and rebuild the whole structure, like-for-like*. This would almost certainly mean including some additional matching bricks - if you don't have any/enough, you could have some made by a specialist traditional brickmaker. You may know of one near you, but if you don't then I can recommend the following from personal experience:-

http://www.bulmerbrickandtile.co.uk/

* If your house is listed, like-for-like repairs do not require Listed Building Consent.

 

[agbagb]

I would still want a full understanding of why the arch failed in the first place.

Does that beam (that supports the centre of the floor above) move when a few people are walking /bouncing upstairs?
This should answer the question:
Does the arch need to support anything other than the brick infill from the arch to the beam?

If Yes then the current strap or flat bar and a total rebuild will not be a reliable long term fix.

If No and a bit of bounce in the floor above is safe and acceptable? Then as long as any movement isn't transferred as loading (eg. no packing between infill and beam), then the strap might be enough to stop a sudden collapse of the bricks.

Please consider, that the design that has survived is not a working safe structure , 99 time out of 100 we don't have the evidence of what didn't work. Or the original design was sound and later removal of lateral restraint to the arch or degradation of materials or additional loading has caused failure.

With proper reinforcement (hidden or visible) the existing structure can be safely preserved. With proper reinforcement (more than just on iron bar to sit the arch on) it can be recreated with structural integrity. To design either solution would require either overkill using structural lintel or a more delicate approach based on an understanding of how arches work.

There are so many factors to consider, I would advise keeping an acro prop under it for now and to take your time researching and thinking over a solution you will be happy to live with in the long term.

 

[Flyfisher]

I may be wrong, but I've always thought that the iron bars under fireplace arches were essentially a temporary requirement to support the arch during construction only. When the mortar had set, the arch would be self-supporting and the iron bars were only left in place because it would be too much trouble to remove them. If this is correct, then it may also be why these iron bars tend to be fairly small (in my limited experience), because they only have to support part of the arch during construction.

In this case, however, the situation is reversed - the arch is not reliably self-supporting and the iron bar has been added as a permanent, load bearing, structural solution. To my amateur eye, and considering the size of bressumers in large open fireplaces, the ironwork looks somewhat 'light' considering the structural task it is being set.

Perhaps it would be worthwhile to seek a professional structural engineer's opinion?

 

[surreysteve]

Hi All

Thanks for all the posts so far - I have taken away some very useful tips.

Obviously, whilst I have tried to post as much information as possible it is not always possible to convey the full information.

The house is indeed G2 listed and planning and conservation consent was granted for the renovation 4 years ago. The fireplace is the last bit to be done. All the previous work was supervised by a conservation surveyor who specialised in oak framed medieval buildings. He was sufficiently skilled that our local conservation officer just kept a watching brief after the initial reports.

Hence, it is pretty much known (from the surveyor/co) that the arch bears no load aside from the bricks and also that it is self supporting without acros. In fact after the plaster was originally stripped it was then in place for 2 years with no support. The acros were only put in place for the final cleaning off as further concrete was removed. NB There is a thick layer of render on the back of the bricks which will remain in place.

The opinion at the time (4 years ago) was that a good repoint would add to the strength (of the already self-supporting arch) but that a further metal support would not hurt to further stabilise things.

On the other note, I take on board the point that it was a poor original design, but I think an interesting poor design that I am quite willing to preserve. I understand this is a personal view and others may prefer to rebuild. As to dates it was built sometime during the 16c and was probably in place for c400 years before it was 'ruined/strengthened' after failing in the early 1960s. So a failed design maybe, but it has outlasted 95% of the houses built in the UK. So perhaps not too bad for a bunch of peasant builders?

I do have some very old small bricks I can use to replace on a like for like so will keep this in mind for filling gaps and replacing unworkable bricks.

I will post pictures here of the final results.

Thanks again for comments and help so far.

Steve T