Don't know what to do with this...

This!!

Agreed.

As a young woman she will experience lots of men looking at her 'funny' because that's what many do. Unfortunately it's a learning process we go through, especially when she goes out to pubs and clubs. Basically leering, which is as prevalent today as it's always been.

The younger generation has been raised to call out this behaviour/express when they feel uncomfortable, which is positive. However, it's a brief look, a young man turning round and looking probably wow she's attractive, bored on a smoke break.

It doesn't sound sinister, a glance, and as you said you can't understand how this even happened. So I do think she's most likely creating attention, wants BF to be jealous, play being so offended.

What's the point of creating an issue, possibly jeopardising his job, for a tiny moment which she will most likely forget the next day?

Sounds like a typical teenager riling up her boyfriend and attention seeking.

I'd have a discrete word with the guy in charge of your build and say the teenage girl next door is feeling uncomfortable due to a couple of the lads and could he give them gentle nudge to make sure they're not doing anything to make her feel that way.

I think her bf was incredibly mature to approach you the way he did and although there may or may not be an issue with the way the lads are behaving, a gentle reminder to be respectful can't hurt.

So if the 16 year old girl came and told you, I would maybe have a subtle word about upsetting the neighbours..

The bf... is it him who doesnt like how the builder looks ar her? Keep out of it

Reading some of the responses on this thread it it quite clear why girls and young women don't feel able to raise concerns about predatory behaviour towards them, or worse still SA. So many MNetters posting here that teenagers are too immature/over dramatic/sensitive/showy offy/downright liars...
Reading these comments has sickened me, especially in the light of the top news stories over the past week.
Young people deserve better from us.

I assume this is an ill judged attempt at humour? Because if it's not you are either a) a massive 🚩
or b) a time traveller from 1970s.

Immature, jealous, over sensitive, over the top to name a few.

People are trying really hard to discredit the teens, aren’t they?! The OP explained you can get from their garden to their parking space which is across from her house. Is it “fishy” that the daughter may use it as a way in and out of her property? Really?

This is a UK based site and unless OP says otherwise, it is assumed she is in the UK too. Our driving age is 17.

They can where I live.

None of us? we didnt all say the same thing....
I also have a 16 yo daughter and she's quite mature and sensible. Sometimes she gets things wrong, but so do adults.

I remember this as a teenager just minding your own business and builders start wolf whistling you, lorry drivers too. Leering. Smirking. Staring. I've even seen it since as I lived near a school and workmen would 'look' at the girls walking past on their way to school. Men do look at women "funny" and make them feel uncomfortable. The boyfriend brought it to your attention. He might have his own issues but that doesn't mean the girlfriend wasn't made to feel uncomfortable by one of your workmen.

Go and speak to her mum and see if you can find out what actually happened. Im sure you dont want to upset your building work, but if the 16 year old girl is upset or frightened you do need to do something. Or at least be aware of whats going on.

We don't even know if the girl herself knows anything about this.

I think I’d just say to them to “be a bit careful as a young lady nearby apparently seems to think she was looked at a bit funny, whatever that looks like; who knows what that means” with a shrug of your shoulders and a confused gesture.

That way you are giving them a warning to behave if warranted, or a be careful if it was misinterpreted. You aren’t insinuating, just passing on a message.

There's too much speculation here but I think if a child in your neighborhood has felt uncomfortable by the actions of someone working for you, you have at least a bit of a responsibility to find out more. Why not ask the girl or her parents what she means. I get that it would be awkward to raise if you then had to but you could just pass on that you've had a complaint that one of the workmen had made a girl feel uncomfortable and leave it at that.

I said that earlier but OP didn’t say anything 🤷‍♀️.

I don’t think anyone has been particularly horrible have they? But I’m pretty gobsmacked at the balls of a 16 year old boy (OP said he looks the same age) to knock on a complete strangers door late in the evening complaining about their builder looking at his girlfriend when neither of them seem to have asked the girls own parents about it. If your 16 year old son said ‘mum, my girlfriend says this and that’, wouldn’t you say ‘tell her parents’? The whole story comes across as weird, he has never met OP or her husband before yet felt ok to tell them all about what their builder has been doing?

Edited to say he’s not ‘helping her to address it’ is he?

Well quite. That means an adult who can drive would be with her too since 16yr olds cannot drive. It's all sounds very fishy.

As I have to remind my children a thousand times a day when one accuses the other of looking at them in some kind of way: we can't control how or where people point their eyes. I don't think there is a way you can say to the workmen "please do not stand outside and look at our neighbours" without causing bad blood. That is, unless you have evidence that he was in fact letching on her, which would be an awkward but more justified conversation.

If you see the boyfriend again, I would maybe say that you did not take any action on this one occasion as the builders will be gone soon, but if the girl is really upset or worried, to get her parents to contact you.

I don’t necessarily think the OP shoukd say anything to the builders since they’ll be gone soon. But, I’m quite astounded at how horrible posters have been about the boyfriend, the daughter and teenagers in general on here.
Sadly as a 16yo girl she has probably already her fair share of grown men “looking at her funny”. Why should she just up and shut up?
Her boyfriend is helping her to address it. How is that a problem / red flag? And those saying the boyfriend should approach the builders himself (or that she should?!). I’m going to assume he’s also around the same age as her. Is he really going to feel confident or safe going directly to the builders whom i’m guessing are adults and quite a bit bigger than them. What would you want your DS’s to do in this situation?

OP explained they have a parking spot by OPs house.