UK Building Regulations - size of an opening on an external wall 3

[SKD_BW]

Hi all, this has been bugging me for a while so I wanted to see if anyone could give any clarity on it?

My query is in relation to UK Building regulations Part A - Section 6.7.3 Openings and recesses. The regs states "no opening in any case should exceed 3m" - W1, W2 or W3 < 3m - as shown in extract below:

My question is, how can biofolding doors or entrances into extensions above 3m ever be allowable under the building regulations? A quick google search shows bifolds are manufactured up to widths of 8.4m - hence this rule does not seem to be enforced.

One obvious statement would be to use a portal frame (i.e. wind posts / goal posts) however it states "under no circumstance" hence, a portal frame would still not be compliant.

Over the years I have worked on multiple projects which have openings bigger than 3m and this has never been questioned by the buildings inspector - is this simply ignorance, or is there a reason this rule can be exceeded? I have read this section of the building regulations probably monthly for the past 5yrs and this statement has never sat right with me. Is there something I am missing?

Thanks in advance!

 

[kipfoot]

My guess is that this is a prescriptive guideline that a mason can use to layout an opening and that if you want something bigger, you need to have a structural engineer figure it out.

However: I'm not in the UK, have never seen this code before, and spell centre with an 'er' at the end.
[URL unfurl="true"]https://www.labc.co.uk/news/what-has-x-factor-got-do-building-regulations[/url]

 

[LittleInch]

It's the difference between "should not" (firm advice) and "must not" (obligatory).

To go against a "should not", you normally need to show how you've allowed additional support or doing something more than the minimum.

That's always the problem with regulations, they are way behind what people actually want or do. Bi fold doors weren't heard of 20 yrs ago so they didn't think about them.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[SKD_BW]

Thanks kipfoot - thanks for that link, I read that page this morning but I am still unsure on the maximum width of w4. Also unsure of when an opening is classed as either rw3 or w4.

My understanding is the UK Building Regulations are always enforceable and the rules should always be complied with. Below statement taken from the building regs:

"First, if a person carrying out building work contravenes the Building Regulations, the local authority may prosecute them in the Magistrates' Court where an unlimited fine may be imposed (sections 35 and 35A of the Building Act 1984). Prosecution is possible up to two years after the completion of the offending work. This action will usually be taken against the person carrying out the work (builder, installer or main contractor)."

Obviously, this would only occur if there was a major incident (failure) - however, in the event an opening was greater than W3, if the structural engineer deemed the opening to be safe (but still in contradiction of the Building Regs), is this acceptable.

Understand this is quite a specific problem, however I suppose this is a larger question in regards to how structural engineers and architects should use the Building Regs - and when (or if) is it ever acceptable to contradict the regs.

For matters such as fire regs, this is fairly descript. I suppose the grey area is for structural alterations or boundary clearances where the Regs provide clear geometrical rules that cannot be complied with.

 

[SKD_BW]

Fantastic point LittleInch

So I suppose, if an opening was bigger than 3m (i.e. W3 > 3m) - but the engineer used best practice and sound engineering judgement / rationale, contricting this rule would be acceptable?

 

[LittleInch]

I believe so.

Often you see something say

Xxx should not exceed yyyy unless ZZZ is in place.

I installed a 3.6m wide set of windows using a certified catnik, which stated it was suitable for openings up to 4.5m wide. That seemed to make everyone happy.



Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[SKD_BW]

Thanks - that makes me feel better. The building regs can tie you in knots at times, but I suppose that is why they are so difficult to write as they aim to be applicable to whole of the UK and domestic properties vary so much.

Exactly there are plenty of bifolding doors, catniks, lintels etc. available "off the shelf" greater than 3m, but reading the regs you would struggle to find an application for these - which is clearly not the case.

 

[Seng1984]

Section 2 of Approved Document A provides prescriptive guidance for sizing 'certain residential buildings of traditional construction'.

Provided all of the various limitations of the section are adhered to, explicit consideration of wind loading etc. is not required and the walls can be sized straight from the document.

I would draw your attention to diagram 3 which notes that any walls which do not comply (eg: walls with openings larger than 3m) are considered 'outside of the scope of this part'. That is to say, you need to consider all loading and justify its construction and stability via explicit calculation.

 

[GeorgeTheCivilEngineer]

An architect can pick up Part A and if they follow the rules, essentially they don't need an engineer.

If they deviate from the rules then an engineered solution is usually required.

I offer a low fee to architects for a 'part A review' - so I just review their layout and make comments where it doesn't conform. Building control used to do this but rarely get any decent review these days.

If they want something to not conform then I charge them for a steel/masonry panel/wind post design.

It is important to note that Part A is out of date and a dumbed down version of BS 8104. In particular the need to move to wider cavitys to get sufficient u-values has made the buttressing rules in Part A redundant.