Green Building Forum - Engineers and overly safe design

Engineers and overly safe design

tony — Wed, 18 Jan 2017 22:29:06 +0000

How much are 'we' paying to protect engineers PI insurance?

"We need to use piled foundations (to protect my PI insurance)" , they explained

Now that we have done soil borehole tests and designed the piles we feel that it would be safer to go down another 600mm (you will have to pay for this extra depth)

We have to pay but were piles even necessary?

There is a 200 year old building within 25m of our site and the building that we are extending is 40 years old and showing no signs of any structural problems.

We still need piles.... but why??? -- see above

Engineers and overly safe design

gyrogear — Thu, 19 Jan 2017 01:36:51 +0000

Posted By: tonyshowing no signs of any structural problems.

not until you start driving the piles, that is

gg

Engineers and overly safe design

SteamyTea — Thu, 19 Jan 2017 07:09:18 +0000

Sounds more like you need to get a second opinion, not all 'engineers' are equal.

Engineers and overly safe design

nigel — Thu, 19 Jan 2017 10:38:56 +0000

Thats the norm for consultants they over specify to cover themselves and often because increasing the cost increases their fees.

I would tell them that next time you will be going elsewhere.

I have an engineer who makes sounds judgements on safety margin and I respect that and use him without question as I trust him to come up with a solution that is workable, safe and economic, thats their job.

Engineers and overly safe design

DarylP — Thu, 19 Jan 2017 10:41:23 +0000

@Tony, the excess on their policies.....?

Engineers and overly safe design

tony — Thu, 19 Jan 2017 12:55:24 +0000

Nigel, yes this is tricky problem ".....because increasing the cost increases their fees."

This is widespread, even commissions from contractors, etc

How can we get to a sensible place on this?

Engineers and overly safe design

CWatters — Thu, 19 Jan 2017 13:04:44 +0000

Our SE put so much steel in our roof that the earths magnetic field has changed and birds are flying the wrong way.

Engineers and overly safe design

gyrogear — Thu, 19 Jan 2017 13:33:58 +0000

Maybe they *bill you* for lot of steel, then the contractors remove it when nobody is looking, and use it on the next site...

gg

Engineers and overly safe design

djh — Thu, 19 Jan 2017 15:34:11 +0000

I had three engineers. One for the main body of the house, chosen because he was happy to sign off straw structure. But he wasn't happy with (de)signing a passive slab foundation, though he regularly does concrete raft designs, nor was he comfortable with a complicated timber roof structure so I had separate engineers for those. Oh, and the first floor structure was (de)signed by the supplier's engineer.

Engineers and overly safe design

joe90 — Sat, 21 Jan 2017 11:42:38 +0000

I have the same problem with my I beam roof, I know it is alright in fact the companies website shows it will work. The supplier says the "computer" won't allow it but this contradicts with their own website details. I have been told to go to a structural engineer but I don't always think they are required in such cases ( and I don't see why I should go paying again to get yet another opinion. )

Engineers and overly safe design

dimengineer — Sat, 21 Jan 2017 11:51:55 +0000

I shall have to defend my profession a bit here. Yes, Engineers can be a bit conservative; this is doubly so for structural engineers (in my experience - I'm the chemical variety). However, in the end, if it does go wrong, they are the ones who are up in front of the judge, not you. That does change one's perspective somewhat.

Engineers and overly safe design

joe90 — Sat, 21 Jan 2017 12:12:23 +0000

Posted By: dimengineerI shall have to defend my profession a bit here. Yes, Engineers can be a bit conservative; this is doubly so for structural engineers (in my experience - I'm the chemical variety). However, in the end, if it does go wrong, they are the ones who are up in front of the judge, not you. That does change one's perspective somewhat.

Dimengineer, not having a pop at your profession at all, I am having a pop at people that have access to information and knowledge of professionals but still choose to rely on insurance backed "others", I know I am not risk adverse.

Engineers and overly safe design

SteamyTea — Sat, 21 Jan 2017 13:26:10 +0000

It is a bit like the difference between Climate and Weather, it is hard to know if SE are cautious because of their professional responsibilities or if the insurance companies have forced them into it.
There will be a lot of variation between SEs but only a few insurance companies underwriting those risk.

I would not like to use a professional that does not have insurance.

Engineers and overly safe design

TimSmall — Sun, 22 Jan 2017 17:53:39 +0000

Some observations (I'm not a structural engineer, but have done some structural calculations). I don't have a lot of experience with commercial SEs, but my impression is:

. The SE will often have no knowledge of the ground conditions, in some instances employing a geo-technical engineer to give you an allowable bearing pressure will pay off (mine gave one 6 times higher than the default value normally used as far as I can remember).

. The Eurocode load assessment methods can often produce worst case loads which are half that of the UK standards, but they are rarely used (especially for small one-off projects - the old 'withdrawn' British Standards are often used). This may change over time, but the EC load assessment methodology is a *lot* more complex than the old BS one, and really requires software (which many SEs still don't use). In particular, small domestic SEs seldom use it (many haven't been trained in it).

. An efficient design takes more time, the additional cost may not be worth it (particularly for one-off projects) - e.g. 30% material reduction might take two to three times as long to calculate by hand (and in some cases might only result in a 10% saving once you've got to the end of the more complex calcs).

Engineers and overly safe design

dimengineer — Sun, 22 Jan 2017 18:40:26 +0000

Posted By: joe90
Posted By: dimengineerI shall have to defend my profession a bit here. Yes, Engineers can be a bit conservative; this is doubly so for structural engineers (in my experience - I'm the chemical variety). However, in the end, if it does go wrong, they are the ones who are up in front of the judge, not you. That does change one's perspective somewhat.

Dimengineer, not having a pop at your profession at all, I am having a pop at people that have access to information and knowledge of professionals but still choose to rely on insurance backed "others", I know I am not risk adverse.

Thats OK, not accusing anyone of having a pop. Just trying to give the view from the "other side" if you like

Engineers and overly safe design

Mike1 — Sun, 22 Jan 2017 20:00:38 +0000

There are various ways of physically testing piles for adequacy, however on a domestic job adding another 600mm to the length is virtually certainly to be the cheaper option.

I would imagine that the 200 year old building would have been built using either a traditional timber frame or lime mortar, either of which would allow the building to flex if / when the ground moves, and that as a result walls may not be plumb or flat, and floors and ceilings may not be level and flat either. Generally people prefer their buildings not to do that these days, and many modern materials aren't able to withstand movement to that extent either, so standards are more rigorous, even than they were 40 years ago...

Engineers and overly safe design

djh — Sun, 22 Jan 2017 21:55:02 +0000

I think the difficulty is that sufficient people think that if something moves or cracks the correct thing is for the builder to fix it, or sue the builder until he does. Then the various third parties with an interest - mortgage companies and insurance companies - insist that the building is built to industry-agreed standards. In the case of foundations, that means the NHBC standard, which is fairly prescriptive. And that's become so usual that building inspectors look for it as well, even when it's not a requirement. It's much like the approved documents, in effect.

And as people have said, it's usually simpler and cheaper to go along with it than argue the toss. I did persuade my engineer that it didn't matter if my garage heaved a bit, especially if it heaved the same amount as the drive in front of it. So he agreed we could do without a big deep hole filled with hardcore underneath the raft.

Engineers and overly safe design

tony — Mon, 23 Jan 2017 17:11:12 +0000

Well done.

Engineers and overly safe design

vord — Sun, 29 Jan 2017 17:41:03 +0000

Quite agree Tony - I have fallen out with the structural engineering industry myself. It is the minority that are useful. My minority has retired and I have no idea how to find another without a bunch of Â£500/hour consultations to rule them out one by one.

Generally I would discuss and agree with building regs before (and hopefully instead of) employing a structural engineering consultant. I reckon my house won't be the first house that anyone has ever built and there should be some rules of thumb. You'll still be going 2m on the foundations if there is a tree in a nearby county.

The real sillyness for me is when you want to fiddle a little with a 400 year old house where they forgot the foundations. Engineering for me is mostly common sense with a calculation every other week (I'm an engineer myself). I've not found a structural engineer who does the common sense part and I find that annoying.

Structures have changed a bit since my house was built. In the old days they built shallow foundations and used flexible materials. My lime mortared brick wall has sunk a few inches but has not cracked. Modern practice is to use cement which is very stiff so any movement will cause cracks so foundations have to be very deep. I don't know why it is not possible to use lime in difficult builds which would otherwise require the use of structural engineers with piles. Lime would allow the building to take a bit of movement and is very much cheaper than employing consultants with no common sense.

Engineers and overly safe design

Nick Parsons — Sun, 29 Jan 2017 18:27:25 +0000

''....which would otherwise require the use of structural engineers with piles.''

Is that really a pre-requisite? (Winces!)

Engineers and overly safe design

fostertom — Sun, 29 Jan 2017 18:30:31 +0000

If anywhere West Country, try http://pasquibbs.co.uk/

Engineers and overly safe design

tony — Sun, 29 Jan 2017 23:26:09 +0000

I am worried now that the lead designer on the project is keen to have high professional consultant costs as their fee is based on a percentage of the overall project cost ... ðŸ˜¢

Engineers and overly safe design

fostertom — Mon, 30 Jan 2017 08:26:54 +0000

That %age doesn't include other consultants' fees as part of the project cost.

Any 'lead designer' (meaning Architect?) who tries to bump up project cost in order to bump up his/her fees is an idiot.
Far more valuable than a bit of cream on this job, is the whole of the next job, which comes by recommendation from happy clients who haven't been ripped off.

Engineers and overly safe design

tony — Mon, 30 Jan 2017 09:45:37 +0000

Oh good.

Engineers and overly safe design

Peter_in_Hungary — Mon, 30 Jan 2017 11:39:58 +0000

If the architects fee is a %age of the project fee, why should the fee go up if the owner wants gold plated bathroom taps and top of the range hand made floor tiles etc. Why not a simple m2 price? Over here it is a m2 price agreed at the beginning.

Engineers and overly safe design

fostertom — Mon, 30 Jan 2017 15:57:38 +0000

Go beyond that simplistic incentive-structure thinking, instead

Posted By: fostertomby recommendation from happy clients who haven't been ripped off

means that we ignore any client's choice luxury finishes, fancy kitchen etc in the notional project cost that I charge a %age of.

Posted By: Peter_in_HungaryWhy not a simple m2 price? Over here it is a m2 price agreed at the beginning

Better instead to agree the %age at the beginning.
One m2 is not like another m2, as far as intensity of design input etc - and no one, least of all the client, really knows at the beginning what kind of a project this one will turn out to be, what with site constraints discovered, and client's aspirations evolving.

Within that, the project's scope will be adjusted to suit the clien't available budget, and the halfway-fair rough measure of amount of design etc work eventually involved, is the final final project cost.

Engineers and overly safe design

barney — Mon, 30 Jan 2017 17:50:07 +0000

Is the fee really a % of out turn cost

It may have been that way in my youth (and that was on a sliding scale anyway)

Most consultant appointments are fixed fee (based on the predicted out turn cost, but fixed fee, with a scale of charges for "change" nonetheless)

Personally, if the client wants to treat me with the practices of the bazaar rather than as his trusted professional advisor, then I can hardly be criticised for treating him the same way - he's trying to sell me his risk on the cheap, I'm just selling it straight back to him

Not difficult, if you want to use a smaller beam or a shallower found, then do it and sign it off yourself

Regards

Barney

Engineers and overly safe design

nigel — Tue, 31 Jan 2017 08:02:52 +0000

Posted By: barneyPersonally, if the client wants to treat me with the practices of the bazaar rather than as his trusted professional advisor, then I can hardly be criticised for treating him the same way - he's trying to sell me his risk on the cheap, I'm just selling it straight back to him

Not difficult, if you want to use a smaller beam or a shallower found, then do it and sign it off yourself

You have to have a trusting relationship with your engineer and being able to question the engineer without them taking offence is quite a good way to develop that.

I am not sure that accusing clients of selling risk on the cheap is quite the approach I would like to see in my engineer.

Engineers and overly safe design

barney — Tue, 31 Jan 2017 09:26:48 +0000

What do you do for a living, Nigel - just asking. What are the criteria you use when selecting professional advisors

I've no problem with developing the client - consultant relationship, much of what I do is based on repeat commissions from satisfied clients

There are also clients whose focus is "how cheap - and of course you'll be taking full responsibility" - basically, they want to buy my skills (and my PII) at the lowest cost (or at no cost)

Not intending to make this personal in any way, but look at Joe 90's point regarding his roof design "He knows it's right, he just wants someone to sign that off" - but infers that he's not happy to pay for that

Barney

Engineers and overly safe design

nigel — Tue, 31 Jan 2017 16:12:20 +0000

I don't think anyone is suggesting that engineers should do work for free or on the cheap.

Just provide an optimised and cost effective solution to problem but not necessarily one that provides zero risk to the PI.