Architect’s Outline Specification - how closely does this need to be followed?

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Hi, just looking for some advice on something. I’m getting a sunroom/extension built at the back of my house and noticed the builders are using 120 mm thick Kingspan floor insulation boards (TP10/TF70/TW55) whilst the Architect’s Outline Specification states that it should be 150 mm thick Kingspan K103 (so thicker and generally higher quality too I believe). I asked about this and the Architect himself has told me that using 120 mm is still compliant. I’m just a bit concerned that if they are not following the spec what else could go wrong with the build, how closely are they required to follow the Outline Specification before they are breaching some regulations?

I’m located in Scotland.

Thanks
 
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Builders should follow the specification implicitly, and only change things with your prior approval.

Obviously they have used a cheaper/inferior insulation, and whilst it may still perform to the required standard, they should reimburse the costs of the cheaper product.

They have priced the work based on the drawings and specification, remember that always. They may then look to substitute products to their advantage not yours.
 
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Thanks, interestingly the Architect’s drawings show 120 mm boards but his spec says 150 mm.
 
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Thanks, interestingly the Architect’s drawings show 120 mm boards but his spec says 150 mm.
OK that's poor specifying by the designer. He's probably just cut and pasted his last job and not properly checked things.

Typically the drawing is referred to by the builders, rather than any separate text document. So strictly whilst a contractor should check and cross reference all documents and clarify errors and omissions, it's common and understandable for just the drawing to be followed.

Perhaps you now need to check confirm that all documents contain the same details.
 
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120mm (currently) is the more realistic figure.
It's an architects 'oath' to ensure the build is carried out as economically efficiently as possible. If 120mm cuts the mustard....
 
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A whole new, but closely related problem has now come up so looking for some advice on this. I’ve attached some pictures, one showing roughly what we were looking for and two showing what we have got. You can clearly see that the structural steel is at a different angle from the roof and this prevents the ‘floor to ceiling’ windows (delivered yesterday) from going all the way to the ceiling. Clearly the builder knew about this mistake all the way through but didn’t think it was worth mentioning! I’m now left in the unfortunate situation where after over 10 weeks of building and multiple more weeks earlier waiting for things to get started to now have an almost fully constructed sunroom that doesn’t match what I asked for! Any advice on what I should do appreciated. At the very least I’ll need substantial compensation from the builder, as it’s their mistake isn’t it?
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Here’s a clearer picture of the steel itself and the structural engineer’s drawing (architect’s also shows windows going to ceiling).
 

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If dynamite is not an option for the extension and the builder, then it needs to be in-filled above the frame to match the head above the other frame and the roof angle.

The drawing has not been followed as per post #2. How you work out compensation for a building built differently to what you wanted, I doubt know.
 
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How much money have you given the builder so far? I wouldn't be giving them another penny until it's rectified. To be honest, infilling above the door with timber isn't a difficult job but how the steelwork ended up so far out (and why the builder didn't get it remade to the correct angle when they realised) beats me.

I see similar problems regularly, and they often stem from the builders deviating from the plans and making freestyle decisions that end up causing problems further down the line, but also the fact that the architects often only give minimal information on the drawings, meaning the builders have to come up with a lot of their own solutions.
The lack of fully dimensioned architect's drawings and details often stems from the client going with the lowest price, so usually no-one is blameless when issues such as these arise.
 
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clearly that is a c***-up! I suggest you need to have a measure up of the structure against the plans; similarly the window against the plans. Maybe get the architect out as well to do the measure up.
One or the other is wrong. If it's the building then you either have to accept an infill, or pay (or convince the builder to pay for) for a replacement full sized window assembly. If it's the window then I'd be pressing for a new window assembly to to fill the aperture completely.
 
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One or the other is wrong. If it's the building then you either have to accept an infill, or pay for a replacement full sized window assembly. If it's the window then I'd be pressing for a new window assembly to to fill the aperture completely.
The window seems to perfectly match the pitch of the roof - the steelwork looks like it's at a much steeper pitch than shown on the plans.

I'm not sure that the steel posts are necessary either, but that's a question for the SE.
 

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