Gus Potter

This is really interesting, thank you Gus. To take up your point about being a competent person, is it acceptable to do self calculations for your own extension (for Building Control/Insurance etc if you properly understand and execute the concepts? Your demonstration of a  confident, rather than competent builder is pertinent, as a self builder, I've been guided so far by the principle that if it looks wrong, it it might well be, rusty physics A Level notwithstanding (see what I did there?). I'm guessing the homeowner panicked and asked for a second opinion? In my own field, I've had an overconfident rider get on a difficult horse without a helmet, telling me he was 'insured', as if that would somehow protect him.  

There were not many notes on the drawing, so the contractor should have read the one that said props no more than 25mm out of plumb!

 

How is the cross bracing normally done?  Scaffold poles?

9 hours ago, Jilly said:

This is really interesting, thank you Gus. To take up your point about being a competent person, is it acceptable to do self calculations for your own extension (for Building Control/Insurance etc if you properly understand and execute the concepts? Your demonstration of a  confident, rather than competent builder is pertinent, as a self builder, I've been guided so far by the principle that if it looks wrong, it it might well be, rusty physics A Level notwithstanding (see what I did there?). I'm guessing the homeowner panicked and asked for a second opinion? In my own field, I've had an overconfident rider get on a difficult horse without a helmet, telling me he was 'insured', as if that would somehow protect him.  

Hi Jilly.

 

@JillyYes, you can do your own structural calculations and submit them for your own extension but you should be competent. 

 

There are other factors worth some discussion. Here are a couple.

 

The first is to recognise that Building control will make reasonable checks to satisfy themselves that the design meets the Building regulation requirements.  For example, they may check 10% of the maths in the calculations and look at perhaps the stability system. However, it is the responsibility of those carrying out the work to ensure that the provisions of the regulations are met in full.  You could look it another way. If BC were responsible for the design then there would be less of a requirement for an SE say to hold the level of PI cover that they do.

 

Secondly, if you do your own calculations and something goes wrong where do you stand from an insurance point of view? I would recommend that if you are going to do your own calculations then it’s worth having a discussion with your insurer. Before you start.

Edited January 4, 2021 by Gus Potter

8 hours ago, Mr Punter said:

There were not many notes on the drawing, so the contractor should have read the one that said props no more than 25mm out of plumb!

 

How is the cross bracing normally done?  Scaffold poles?

 

@Mr PunterYes usually with standard scaffold poles which have an outside diameter of  ~48.3mm.

 

The top part of the prop (inner tube) is the same diameter as the scaffold tube so you can make 90 degree connections with a standard double coupler, angled (diagonal bracing) connections with a standard swivel coupler. The outer tube of the prop has a diameter of ~60.3mm so here you use reduction couplers.

Edited January 4, 2021 by Gus Potter