Go Back  PPRuNe Forums > PPRuNe Social > Jet Blast
Reload this Page >

Any Architects or Structural Engineers here?

Jet Blast Topics that don't fit the other forums. Rules of Engagement apply.

Any Architects or Structural Engineers here?

Old 4th Jan 2022, 14:12
  #1 (permalink)  
Ant
even ants need some lovin'
Thread Starter
 
Join Date: Jan 2001
Location: Kent, UK.
Posts: 151
Any Architects or Structural Engineers here?

Would be grateful if anyone could shed some technical expertise on a concern I have.

Our younger son is renting a lovely flat (apartment for our US friends!) in the picturesque city of Exeter in the Southwest of England. The building is part of a crescent of very fine Georgian houses built on the hill just above the quays, and the foundation stone of the crescent was laid all the way back in 1802. It is truly a wonder that the building is 220 years old!!


On our first visit, he straight away invited us to step out onto the balcony in order to admire the view of the Exeter quayside area and the countryside beyond.

Please see picture of the balcony here and note the 8 black supporting brackets under the balcony floor.


Well, I have to say that the very moment I stepped onto the balcony I quickly became uncomfortable. I had imagined that the balcony floor might be made of timber planks or decking of some sort, and was more than surprised and alarmed to find it is seemingly solid concrete or stone with a non slip surface painted on top. On looking further at the balcony structure I noted that additional weight on the 8 brackets is being supplied by the fancy wrought iron railings to the front and sides of the structure with yet more weight from the balcony roof of timber slats with lead flashing. I don't think those 8 brackets are likely to be anything near the age of the building itself, but even if fitted recently and made with modern materials there is a substantial weight on them, and their integrity as supports also depends on how well they are keyed into the building brickwork.


I have voiced my concerns a number of times now to our son, suggesting the balcony should be regarded ONLY as a decorative structure and NOT something to have meals and drinks on in the summertime. I also offered to pay for a firm of structural engineers to inspect and offer an opinion on the structure. Yes, I appreciate that it is the responsibility of the landlord to ensure the safety of the building being rented, but I suspect they would simply put the balcony out of bounds rather than pay for an inspection themselves. Either way, son is now irritated by my interference and lets me know that every time I raise the subject.


Even if both son and landlord were to agree to an inspection, I wonder how such an inspection could realistically conclude the safety of the structure short of carrying out a potentially destructive load test.


Your thoughts, opinions and advice will be gratefully received.

Last edited by Ant; 4th Jan 2022 at 14:56.
Ant is offline  
Old 4th Jan 2022, 15:05
  #2 (permalink)  
 
Join Date: Feb 2016
Location: Southport
Posts: 1,259
My expertise stops at 1st year engineering degree level - I did Physics only from second year onwards but a couple of observations from the street view:

The "identical" balcony to the left has 4 thin cast iron columns going to ground level which your son's does not, but the brackets under that one are considerably less substantial (to say the least...I was a bit worried till I zoomed in and saw the columns - one is hidden by a parking signpost). The spacing of the brackets on your son's balcony is uneven but I guess was chosen so that the load goes down a solid brick wall rather than above the windows or door, which suggests they are meant to take that kind of load. No way of telling just from a photo how far the brackets go back into the wall but I would expect it to be some distance, if it's a double wall with cavity I'd hope they go back to the interior wall for leverage (cantilever load). Also the concrete should have metal reinforcement - again no way to tell if across the slab, in/out or both, and the slab itself might go back some way into the cavity wall and also be a cantilever support.

Looking at it if I was stood on it it would be the thinness of the metal barriers that made me anxious......but it's clearly meant that way to offer as open a view as possible. Modern way is just to use glass which is even worse if you don't like heights....

Most reassuringly.....The balcony has been there since at least 2008 (that's as far back as the Street View goes) and hasn't moved anywhere

Things that have no obvious support always worry me, every time I look at that hotel in Manchester (Beetham Tower) it makes me cringe, I know the designers know exactly what they're doing, but to have that many floors above empty space just looks.....wrong. Which is the intention, but still.....
andytug is offline  
Old 4th Jan 2022, 15:26
  #3 (permalink)  
 
Join Date: Sep 2015
Location: London
Posts: 438
I did all three years of my Engineering course, but it was a looooong time ago, and more of my focus was on trying to be competitive in several different sports than maybe it should have been...

Apart from the cantilever this is no different to the internal structure, which may well have (very heavy) brick walls supported by wooden joists of unknown integrity; it's not unknown for internal floors of older buildings to collapse (often during parties, anecdotally). At least you can see most of the structure of the balcony, and there's no obvious indicator that it hasn't been maintained. Fearing every old/unknown structure is clearly life-limiting, so I tend to rely on the law of averages, and just avoid those that are obviously in a poor state of repair. I also take the view that failing structures tend to give some warning, so if you keep an eye out for movement, and avoid significant increases in loads (eg parties) you've probably removed most of the risk.
pasta is offline  
Old 4th Jan 2022, 15:43
  #4 (permalink)  
 
Join Date: Jul 2003
Location: Brum
Posts: 845
A quick Google of the street name brings up an image of an Edwardian post card, replete with said balconies.
It's a bit blurred, but it does appear that the two different balconies have been there since it was built, odd that the two designs are different, the left supported by posts, the right cantilevered off the front wall.

It might be worth a phone around some Exeter structural surveyors - one of them might have looked at the property before, or had experience of similar local properties with similar features...



Nige321 is offline  
Old 4th Jan 2022, 17:00
  #5 (permalink)  
TCU
 
Join Date: Apr 2004
Location: On BA58/59
Posts: 255
What a beautiful building. Colleton Crescent is Grade II* listed.....best left to be!
TCU is offline  
Old 4th Jan 2022, 17:33
  #6 (permalink)  
 
Join Date: Jan 2008
Location: Denver
Posts: 1,114
My initial reaction to the image(s) is that I'd be more concerned with the integrity of the balcony platform itself, rather than the supports. There seems to be a bit of warping or sagging between the braces towards the right side. And indeed, over the ground-floor doorway there appears to be a transverse horizontal brace across the brick wall under the wider sagging segment. Possibly added at a later time.

And if actually concrete (or to a lesser extent stone), it seems like a rather - thin - structure top to bottom - 3 inchesĪ. But that does depend on the actual material, and whether it is stronger in tension or compression. And the expected loads.

(NB - Portland cement only dates back to 1824, and (internally) reinforced concrete to 1849).

Qualifications: 1 year formal study in architecture before departing for more interesting subjects, plus growing up in a family where my dad and three uncles were all engineers in the business of making heavy things not fall down (chemical, architectural, mining, and steel fabrication) - I absorbed a lot by osmosis.
pattern_is_full is offline  
Old 4th Jan 2022, 17:45
  #7 (permalink)  
 
Join Date: Aug 2006
Location: Looking for the signals square at LHR
Posts: 236
I'm not a structural engineer, but would be inclined to think that - supposing the balcony to have been designed by a competent, person - there would have been substantial cantilever integrity because the "hanging knees" by themselves, going by what can be gauged of their ratios, appear insufficient to support any substantial load. I imagine this addition to the building is of fairly recent origin and that drawings relating thereto might be available from the local council, heritage body or similar to whom application might have been made to allow the change. Capacity to absorb vertical loads with a factor of safety could be calculated from these drawings and included scantlings; this would allow "non-destructive testing".

GQ BSc, CEng.

Last edited by Gipsy Queen; 4th Jan 2022 at 17:56.
Gipsy Queen is offline  
Old 4th Jan 2022, 17:54
  #8 (permalink)  
 
Join Date: Jun 2007
Location: Beyond the Blue Horizon
Age: 61
Posts: 954
Ant
I would think that those balconies will have been surveyed at some time relatively recently by either the landlord, or even possibly his insurance company. My company is a specialist in facades of buildings, so we do not look at balconies in facades, apart from where they interface with cladding / curtain walling. If it makes you feel more relaxed I generally find that I spend 99% of my time looking at new building facades, and they create more business for my company, so I would not be so worried. Did you feel any movement when you stepped onto it may I ask ? Also maybe look with binoculars at the mounting points into the facade to see if there is any sign of cracking or movement on your next visit, but I would be a little surprised if there was. As a rule of thumb, generally older buildings have settled over time and therefore structurally are “settled”. Obviously I have not seen the building, so I would have to caveat the above comments with that, but it looks a well maintained building which some of the more modern buildings I find are not, and indeed have been very badly built in the first place.

Kind regards
Mr Mac
Mr Mac is offline  
Old 4th Jan 2022, 18:09
  #9 (permalink)  
 
Join Date: Feb 2006
Location: Hanging off the end of a thread
Posts: 22,886
Gypsy post 4 is an Edwardian postcard showing them “as is”, so not a late edition.

Did you feel any movement when you stepped onto it may I ask ? Also maybe look with binoculars at the mounting points into the facade to see if there is any sign of cracking or movement on your next visit,
And don’t do that if a copper is near or you might get arrested as a peeping Tom
NutLoose is offline  
Old 4th Jan 2022, 20:09
  #10 (permalink)  
 
Join Date: May 2007
Location: Dark side of the Moon
Posts: 325
Originally Posted by Ant View Post

I had imagined that the balcony floor might be made of timber planks or decking of some sort, and was more than surprised and alarmed to find it is seemingly solid concrete or stone with a non slip surface painted on top. On looking further at the balcony structure I noted that additional weight on the 8 brackets is being supplied by the fancy wrought iron railings to the front and sides of the structure with yet more weight from the balcony roof of timber slats with lead flashing. I don't think those 8 brackets are likely to be anything near the age of the building itself, but even if fitted recently and made with modern materials there is a substantial weight on them, and their integrity as supports also depends on how well they are keyed into the building brickwork.
A few points from an architect and structural engineer (although I haven't worked as either for some time):

1) The roof appears to be largely supported by its own set of struts, rather than depend on the wrought iron trellis (this last does not appear to be stiff enough in the vertical plane to support the entire roof, as it would buckle).
2) the 8 brackets would most likely be fixed to the wall with bolts or anchors, possibly in addition to being partially built into the wall. Providing that they are adequately anchored, they look more than capable of resisting the vertical shear load and cantilever moment being applied by the concrete deck (which is transferred to the wall as a pull-out load at the point where the top of the bracket meets the wall).
3) the only thing that would concern me slightly (and this is just from looking at the photograph) would be leaning against the balcony hand rail, as it's not clear how much horizontal load the balustrade could support.

But as the structure has been in place for a considerable time, it's probably over-engineered in the first place.

A survey by a qualified engineer should be able to assess the dead and live loads on the various parts of the structure, do a load take-down (calculate where the loads are being supported, and their magnitudes), and then assess the capability of the structure to resist those loads, using standard values for material strengths of wrought iron, brickwork and fastenings, applying the appropriate factors of safety. A few hundred quid, I'd have thought.

FBW
Fly-by-Wife is offline  
Old 4th Jan 2022, 23:44
  #11 (permalink)  
 
Join Date: Oct 2013
Location: UK
Age: 40
Posts: 539
^ Fly-By-Wife does a pretty good job of explaining it as far as I'm concerned (18 years aerospace structures analysis). It'll be fine if used appropriately.

Note the other Balcony with the supporting struts does not appear to have the brackets - you need one or the other done well. They could have done both for redundancy, but just duplication of effort.
unmanned_droid is offline  
Old 5th Jan 2022, 00:00
  #12 (permalink)  
 
Join Date: Jan 2007
Location: Mostly in my own imagination
Posts: 121
Is your son a gymnast?

<not helpful>

Is your son a gymnast?

The reason I ask is that I heard a story once where a gymnast went to a competition somewhere and checked into his hotel near the waterfront. He was surprised at how pleasant the view was and he leaned on the railing to see more of it. That, of course, is when the railing gave way.

However, now comes the gymnastic part, because he instantly realised what had happened and that he was now going to fall to the pavement far below, so instinctively got into the pike position, did two somersaults with a half twist and nailed the landing ... although he did brake both ankles

You have to appreciate the irony of the situation though, because while it was gymnastic skills that undoubtedly saved him, it was also gymnastic skills that put him in that hotel to begin with


</not helpful>
Sue VÍtements is offline  
Old 5th Jan 2022, 00:11
  #13 (permalink)  
 
Join Date: Oct 2013
Location: UK
Age: 40
Posts: 539
Iron-y railings too, probably...
unmanned_droid is offline  
Old 5th Jan 2022, 00:36
  #14 (permalink)  
Gnome de PPRuNe
 
Join Date: Jan 2002
Location: Too close to Croydon for comfort
Age: 58
Posts: 9,651
Originally Posted by Sue VÍtements View Post
I heard a story once where a gymnast went to a competition somewhere and checked into his hotel near the waterfront. He was surprised at how pleasant the view was and he leaned on the railing to see more of it. That, of course, is when the railing gave way.
That sounds like Jimmy Doolittle who was quite a gymnast and while demonstrating an aircraft in South America in the 1920s, took up a challenge one evening to emulate Douglas Fairbanks by doing a handstand on a balcony balustrade. It gave way and he broke both ankles in the fall.



Last edited by treadigraph; 5th Jan 2022 at 00:56.
treadigraph is offline  
Old 5th Jan 2022, 07:51
  #15 (permalink)  
 
Join Date: Jan 2003
Location: Kelowna Wine Country
Posts: 468
If you look for an engineer you need one with experience in period construction. Anyone else will be charging you for their education! A local builder who has worked on the building might be as useful.

The brackets themselves don't look out of proportion.

As a builder I'd want to know how the brackets are tied to the building, particularly at the top. In those buildings the joists are usually front to back ( so they don't put the joist ends in the chimneys and to locate the front wall. The brackets could be tied through the wall to the joists in which case, supposing they are not degraded, they are going to last another two hundred years. They might just have some sort of flange that hooks in the brick wall itself or right through it and rely on the weight of brickwork above.to keep it in place. Obviously either work

Degradation could occur from water penetration between the deck and the wall. You should look at that area for any way the water could enter.

It looks as though the beam under the balcony over the door was added later, I'd pay extra attention to the condition of the balcony in that area.

Not so worried about the rail as it is stabilised by the vertical portions up to the roof which prevent the bottom being 'levered' out. Relatively short rails between them. Personally I am afraid of heights so don't lean on any rails more than six or seven feet above GL.

When I dismantled the walls of our house (100 year old terrace in Portobello Road area) the mortar was just powder. You could lift the bricks off just by picking them up. The first three floors were three bricks thick so if the deck cantilever is held by weight there is probably a good deal of it!
ChrisVJ is offline  
Old 5th Jan 2022, 08:07
  #16 (permalink)  
 
Join Date: Aug 2020
Location: UK
Posts: 25
maybe you can cat/dog/rubber plant sit sometime and sneak an engineer in whilst progeny is away..
arf23 is offline  
Old 5th Jan 2022, 09:21
  #17 (permalink)  
 
Join Date: Mar 2019
Location: Vantaa, Finland
Posts: 0
Looks like the balcony on the left has been repaired/modified at some point, RHS post did not exist the time of construction. The cast iron brackets look like they could be original.

Three things to check: corrosion on the brackets and as someone said, the fixing to the wall at the corner and fracturing of the balcony floor slab. On old buildings the bad ones are culled out but ageing does happen, here the good thing is that the basics probably are ok as it has survived so far.

Old buildings like this were not designed in the sense we do it now. They were designed by experience. There usually are no clear load paths, everything depends on everything and modifying anything can be a nightmare. Have done it a few times, never ever as I succeeded the first few times.
Aihkio is offline  
Old 6th Jan 2022, 03:09
  #18 (permalink)  
 
Join Date: Mar 2005
Location: N/A
Posts: 4,445
Would the plans/buiding approval files still be extant in some archive?
megan is offline  
Old 6th Jan 2022, 06:17
  #19 (permalink)  
Ant
even ants need some lovin'
Thread Starter
 
Join Date: Jan 2001
Location: Kent, UK.
Posts: 151
Thanks all for your replies.
Some interesting details to follow in a day or two.
Ant is offline  
Old 7th Jan 2022, 05:39
  #20 (permalink)  
 
Join Date: Oct 2019
Location: USA
Posts: 179
Typically, such porches have a member that extends back into the building so that only a small portion of the support is outside, forming an effective pry bar to hold the weight.

If that's not the case then there are two parts to consider. One is that the connection to the building needs to withstand the shear load - that is the force in the vertical direction that would, if allowed, cause the porch to slide down the face.. The other is the moment or leverage that the porch applies to the connection. If there is an average weight of 1000 kg at 1 meter from the face then that is 1000 kg-meters of moment. On those brackets, if they are 0.3 meters, then the top needs to apply 1000 kg-m/0.3 m or around 3000 kg of tensile force. Of course, to balance that, the bottom of the bracket has to push away from the building the same amount. In engineering this would be multiplied by G (9.81m/sec^2) to get Newtons - the actual measure of force. However that seems to be widely abused so I'll leave it here.

Both forces would need to be resisted by suitable fasteners though shear could also be handled separately by resting on a small ledge.

If there's not a continuous beam leveraging the brackets, it's possible there are steel straps to the tops of the brackets extending back into the building, similar to the thin straps that appear under the other porch. These straps are then bolted to the floor framing. The disadvantage to straps is they are relatively thin and can corrode where they exit the building and are often difficult to inspect.

Factors in favor of it being safe: It's been there a long time. A lack of rust staining, a usual indicator of uncontrolled corrosion. If there isn't sagging.

In any case it really requires a competent building engineer to evaluate it as there are endless amounts of deception and mistakes that can mask the true nature of the construction. I would not ask an architect. They are more involved with the way people interact with the building rather than the way the structure functions. In the US a licensed structural engineer signs off on detailed building plans - not architects.

Mention that the building in Florida was standing up until the moment it wasn't.
MechEngr is online now  

Thread Tools
Search this Thread

Contact Us - Archive - Advertising - Cookie Policy - Privacy Statement - Terms of Service - Do Not Sell My Personal Information -

Copyright © 2021 MH Sub I, LLC dba Internet Brands. All rights reserved. Use of this site indicates your consent to the Terms of Use.