Redoing an attic

[saveasteading]

Timber works the same as steel. The principles are the same, but the product is more variable., and it is easier to adapt.

[Garald]

11 minutes ago, saveasteading said:

This sort of stuff?

 

Elastic section modulus

Equation (9.10) may be written in the form

σx,1=MZe,1σx,2=MZe,2

in which the terms Z_e,1(=I/y₁) and Z_e,2(=I/y₂) are known as the elastic section moduli of the cross section. For a beam section having the z axis as an axis of symmetry, say, y₁=y₂ and Z_e,1=Z_e,2=Z_e. Then, numerically

σx,1=σx,2=MZe

 

From

Dr.T.H.G. Megson, in Structural and Stress Analysis (Third Edition), 2014

 

- looks like fun. The more maths/physics there is, the more readable it will be for me.

[Garald]

3 minutes ago, saveasteading said:

Timber works the same as steel. The principles are the same, but the product is more variable., and it is easier to adapt.

 

You mean for us to adapt to it, or for someone to work on it and make it suitable?

[saveasteading]

4 minutes ago, Garald said:

for someone to work on it and make it suitable?

Diy. Saw, hammer, nails. 

[Garald]

OK. So, open challenge: recommend books that are reasonably concise and heavy on the reasons behind things; mathematical content a big plus (goes together with being concise).

 

 

[Garald]

Otherwise put: OK, maybe there is no such thing as engineering books written for mathematicians, since perhaps not enough mathematicians are curious about statistics. But what is the statistics equivalent of Feynman's lectures or the Berkeley Physics Course? (On these two examples: neither is ideal for me *now*, since they assume less mathematical maturity than I have, but they can be very good fun.)

[Gus Potter]

34 minutes ago, Garald said:

Of course I risk annoying an SE by 'double-guessing', but OTOH I completely agree with your philosophy:

You are paying the fee. There are plenty SE's about that take the view .. pay me a fair days rate, recognise my skills and craft.  I run my business not on price but on my skills.

For all on BH you'll be happy to pay £250 and hour to your lawer but get an upset tummy if your SE charges you 80 - 100 an hour.. but your lawer is not going to save you say a week on site for a couple of men that will run up a bill of 1.5k a week?

 

An Architect with 40 years experience behind them will save you piles of cash too! If they can't then get rid and come to me @ETC

 

About every month I have someone that declines one of my briefs. The reason.. I can get an SE for half the price.. but I know that the builder is going to rip the absolute pish out them.. I also see some of my competitors  SE desings.. and sometimes they are downright dangerous! Yes the beams say in themselves may take the loads but the buildability / sequancing  can't be realised at an affordable cost...and that makes their design dangerous! They know it, they know I know.. and they shite their pants when I get called into to inspect their design! cause I'm a builder come gamekeeper!

 

Scottish SER scheme.. story for another day.. but maybe that is the police policing themseves? Surely not! Does that mean that Scottsh SE's are better than Irish or English SE's? Funnily the Scottish SER Scheme is an English registered limited company.. the smell of roses is overwhelming!

 

@Garald Spend some time finding the right SE  for you, don't go for the cheepest, find an honest broker, go for the one that will deliver what you need

 

 

 

 

 

[Garald]

2 minutes ago, Gus Potter said:

@Garald Spend some time finding the right SE  for you, don't go for the cheepest, find an honest broker, go for the one that will deliver what you need

 

Completely agreed. I won't be looking for the cheapest - I'll be looking for an SE who besides doing a good job will not be annoyed by @Garald always asking why.

(Oh, and will actually be interested in not doing things in the most standard, boring way. Plenty of people in the Paris area just scrap everything in the attic and build something very standard from scrap, I take. My feeling is that if the task actually forces the engineer to put serious thought into the issue, the end product will be much better.)

 

> An Architect with 40 years experience behind them will save you piles of cash too!

 

Well, it seems that due to legal requirements I'll need to go through an architecture studio no matter what. I suppose the algorithm is to ask around for an SE that works in an architecture studio, and choose the studio in which that SE works?

[Gus Potter]

59 minutes ago, Garald said:

Well, it seems that due to legal requirements I'll need to go through an architecture studio no matter what. I suppose the algorithm is to ask around for an SE that works in an architecture studio, and choose the studio in which that SE works?

I do a good few attic conversions in my day job. Some require a bit of ecclectic engineering /  design and that often drives the viability in terms of cost. Many Architect's just don't have the SE knowledge to excecute this at an effective cost. I'm surprised that you have to go through and Architect's studio. I carry £2.0m PI insurance but most of the Architect's / domestic light industrial Architectural designers carry less than a £ 1.0m as a day to day working policy. This reflects the responsibility that SE's carry to be blunt!

 

To be fair I have a big tool box of stuff I've learnt over the years . I know when I have a good chance of sistering joists, when I need steels, can I use cold formed steel, glulam beams, can I plate up the existing roof joist connections with plywood and glue.. can I just shift a bit of load elsewhere in an old roof to make it work?  will it be ok just as it is! But here we need to look at how an old roof is made. Is it a true cut roof or does it rely on nails that may have corroded?

 

It's not just the structure per say.. often you have drainage requirements that has to be weaved about the structural members. I wear two hat so I'm an SE and Architectural Designer.

 

But.. I also collabrate with Architects where I just do the SE stuff for them. What they do is to say.. hey Gus.. I want to do this project.. can you have a look over it and see where you can save some cash..squeeze in the stair case so they can then go back to the Client and say.. our SE has had a look at this and we think we can do x, y and z Arcitecturally and here is how we are going to make the savings to pay for it. This can mean getting a traditional joiner that has been on their books for a long time and the Architect wins the job on their access to the right contractor and SE.

 

Now here is a small example. In a traditional roof you have some vertical struts. In Scotland we call them soldiers. These struts are commonly 1/3 checked. The check acts in direct bearing..timber to timber  the other part has commonly three nails only that stops the rafter lifting up. In other words this simple joint is more comlex than  it seems at first glance. One part of the joist resists wind uplift ( the nails) the other say downwards snow load. Once you are aware of how a checked roof joint works you can begin to appreciate how skilled the joiners were.

 

That's it for now.

 

 

 

 

[Garald]

8 minutes ago, Gus Potter said:

I do a good few attic conversions in my day job. Some require a bit of ecclectic engineering /  design and that often drives the viability in terms of cost.

 

I'll be glad to pay an SE - and the joiners, and other people doing the physical work. As for some of the people that get in the middle...

 

Of course part of the idea of reusing the existing structure is to reduce waste (it seems a bit to scrap something that has lasted almost 100 years and that looks rather nice in my view) and also to reduce labour (and material) costs by avoiding *unnecessary* manual labour.

[Garald]

Since the system apparently deleted the photos in my original post, let me add a couple here, to make clear what things look like now - the attic has already been renovated, and it's a nice space; it's just that there's not a lot of head room and the insulation is very middling.

 

Attic with cat:

 

 

(There's also a bathroom and a bedroom/second office.)

 

Here's what the area in the second picture looked like when the two skylights where about to be opened; the insulation material in that bit of the ceiling had been removed and was about to be replaced (by rockwool I think). There's still an issue with cold air circulating within the ceiling.

 

[Gus Potter]

32 minutes ago, Garald said:

 

Of course part of the idea of reusing the existing structure is to reduce waste

I agree. It's a good appoach to let sleeping dogs lie. The existing roof will likely be restraining the existing wall heads. Often in the Uk we used what is called a pole plate roof. Here there is a timber runner that locks the rafter base to the ceiling joist.

 

I'll dig out a photo, not tonight but later if of any interest.

 

The more you mess with an existing roof the more risk that it will move. If you have a period property then you get no prizes for cracking the walls!

 

Now this may not apply to you but many old walls rely on having a good amount of compressive load from above. Sometimes we can "unload" an old wall and we think that will be good for it.. but in fact it can be very bad! At first glance this is counter intuitive but the compressive load keeps the say soft lime mortar in compression. Masonry walls perfom well if they are subject to reasonable compression. In laymans terms this helps keep the joints tight., and by default water resistant.

 

I could show you the maths but lets stick to concept ideas for now.

 

Edited Friday at 02:27 by Gus Potter

[Garald]

1 hour ago, Gus Potter said:

I agree. It's a good appoach to let sleeping dogs lie. The existing roof will likely be restraining the existing wall heads. Often in the Uk we used what is called a pole plate roof. Here there is a timber runner that locks the rafter base to the ceiling joist.

 

I'll dig out a photo, not tonight but later if of any interest.

 

 

By all means do!

[SteamyTea]

6 hours ago, Gus Potter said:

When I was a builder I did not know how to teach myself! @SteamyTea @MikeSharp01does this make sense to you

Autodidact.

 

 

[Gus Potter]

46 minutes ago, Garald said:

By all means do!

 

Rotate the image +90 degrees. i.e clockwise. The pole plate is the ~ 50 x 50 mm timber that locks the rafter to the ceiling joist.

 

The simplicity of this connection is remarkable but this is not taught at university... and you won't find this in standard text books. What you will find is plenty Architects / builders and other historical types  talking about this but few actually know how it works @ETC fancy a go?

 

Just kidding you.. The primary forces are the gravity loads,  wind uplift, timber shrinkage and creep.

 

Now you live in France.. so you'll have some of these stunning winding stone stair cases that seem to be supported by sky hooks.

 

We know they work and why qualitatively.. like the pole plate above... but if you get some twat from your approval authority that says.. lets see some calcs. It  is very difficu to prove it by calculation. Even when you can you find that many old buldings and their structural membesr can't meet the moderns design loadings.

 

When this happens we as SE's need to delve deep in our basic maths, we have a look at probalility and risk of over stress. and all the while folk are slagging us off and not willing to pay for us keeping their kids safe?

 

I've got some high end soiftware that does finite element analysis.. it could maybe come close but it could take me about a week to set up the model.. then I need to verify that my model is rational, then explain to some (expletive deleted)wit in the council what it is all about. I would not do this for less than 7.5k... UK pounds. Now imagine if I sent this stuff to your local French Authority. They would / may do one of two things.

 

The smart folk would say.. let's see how the Scots guy is modelling this and the conditions / assumptions he is making in his model. they would use it as a CPD excercise all at your expense.. the rest would say.. we don't like Jocks  so "^ let them have intercourse"

 

 

Still happy to give you a bit of advice though but as you can see from the above I'm a bit of a pragmatist.

 

 

 

 

 

 

[Garald]

4 minutes ago, Gus Potter said:

 

The smart folk would say.. let's see how the Scots guy is modelling this and the conditions / assumptions he is making in his model. they would use it as a CPD excercise all at your expense.. the rest would say.. we don't like Jocks  so "^ let them have intercourse"

 

 

Still happy to give you a bit of advice though but as you can see from the above I'm a bit of a pragmatist.

 

Right, I'm afraid I'll have to hire someone local (and an architect to sign off on things! brrr!) when I actually go through with this. Still, I'm very grateful for all advice I can get here.

 

One of many reasons to find out which possibilities are possible and sensible is that I will need to ask for permission from townhall. I think they care mainly about the external look of things. (Or possibly structural work is the business of another department within townhall?) Wouldn't be fun if I hired an SE first, paid them to do plenty of work, and then found out townhall does not like how it would look from the street.

[Garald]

CPD = Continuing Professional Development?

[Gus Potter]

2 minutes ago, SteamyTea said:

Autodidact.

I admire your intelect, range of knowledge, what you teach and explain. Your command of English blows me away. You have a gift of being able to distill complex subjects into laymans terms. I've just learnt a new word not least.  Thank you. If you are ever up in Weegie land then let me know.

[Garald]

PS. I just have a regular wooden staircase going up to the first floor and then a *really* narrow staircase going up to the attic. I would have thought there would have to be a way to extend the first staircase instead of cramming a narrow staircase in what must have once been a closet, but hey, I don't want to change something that works!

 

 

[Gus Potter]

27 minutes ago, Garald said:

CPD = Continuing Professional Development?

Yes.

 

As Engineers we are always seeking out new ideas. @Kelvin et al.

 

On the AI stuff. But I'm going to give AI a hammering if I have the will to live. Folk are getting carried away with this. For me it's just another IT ( computer development) that we will get used to.

 

As an SE it may make the calculations more speady.. maybe format our reports a bit better. But having been involved in developing software that other SE's use..I've learnt that any software has it's limitations. The basic rule of new software is let's get it out there and we will sort out the bugs later. No shit folks I have been there and worn the tee shirt! Buy the time you sort out all the bugs the world lhas moved on and the investment is lost!

 

AI will be limited by the (expletive deleted)wits that are involved in teaching it. These will tend to be young folk that have litle to no life experience. Itis  potentially dangerous but they said the same about Elvis!

 

The main stream media are making a big song and dance about this.. but to give the young folk credit they can smell shite just the same as us us older folk!

Edited Friday at 05:42 by Gus Potter

[Garald]

Wait, SE is about the last field in which I would think of using AI. The main advance in AI in the last few years is that it has got really, really good at bullshitting. It can write an Op-Ed for a major newspaper, yes, but designing a roof that will not fall?

 

Finite elements was a legitimate revolution in its own bounded field back in the day.

[SteamyTea]

9 minutes ago, Gus Potter said:

but to give the young folk credit they can smell shite just the same as us us older folk

Old people fall for shite as well.  People still want to believe that Walt Disney was frozen.

 

30 minutes ago, Gus Potter said:

Your command of English blows me away

Strange that, I failed English 'O 'Level (both of them).  But then it was really the third language I learnt after Chinese and Dutch.

After that we lived in French and Spanish speaking places, so all got muddled again when I was 10.

For a laugh, and it was a real laugh, I learnt British Sign Language about 25 years ago.

Now that is a sensible and logical language, and you don't have to write anything.

[MikeSharp01]

7 hours ago, Gus Potter said:

When I was a builder I did not know how to teach myself! @SteamyTea @MikeSharp01does this make sense to you?

Yep - learning to learn is more important than learning any single subject and embedding lifelong learning alongside a reflective practitioner approach makes everyday a school day! 

[MikeSharp01]

1 hour ago, Gus Potter said:

AI will be limited by the (expletive deleted)wits that are involved in teaching it.

Well some of them anyway - I teach AI to undergraduate and post graduate engineers, very much tempered by the patterns I have learned about technology and its progress. I am as concerned about the potential of AI as Geoffrey Hinton but I do think it has great potential to help in many places - medical imaging is one, but these are really rather simple AIs. We are just at the find and exploiting the opportunities phase in the backwash of the Large Language Models (LLM) really. Recent research undertaken showing how LLM AI might find ways to protect itself from our intention to turn it off is worrying but for me - and I would not want to hijack this thread as it is a genuine challenge for @Garald, almost none of it is possible without leveraging the services of the big players - such as Google (Tensorflow /Keras) and Meta (PyTorch) so we are slowly moving ever closer to the grip of the corporations for more and more of what we do - this much I have learned.

[SteamyTea]

@Garald

I have been pondering your mathematics and how it fits in with structures.

 

 

I found this, but thought I would let you digest it and write up a in less than 500 words for the rest of us to read in the morning.

 

https://cdn.ima.org.uk/wp/wp-content/uploads/2018/02/MT-2007-Nonlinear-Mathematics-in-Structural-Engineering.pdf

 

This one is interesting as well.  It is about teaching.

 

https://peer.asee.org/using-engineering-mathematics-to-learn-structural-analysis.pdf

Edited Friday at 20:54 by SteamyTea