To tell my manager I won’t share a room with colleague again?

Yes, it costs the company money. Two rooms are £200 in the travel & entertainment line of the operating expenses, vs £100 for one room.

This is a reasonable work expense and therefore it reduces the profits on which the company pays tax by £100, but it’s not free to the company.

ETA op should still have her own room though

I never share a room nowadays, other than with my partner or best friend. I'd refuse and if the employer argued, I'd cite medical reasons. I often seem to succumb to food poisoning when I'm away from home and, quite honestly, there are times when I'd refuse to share a bathroom with me!

You are too nice for your own good. Stop being a doormat.

YABVU for ever agreeing to this arrangement.

I travelled for business for 30 years Op. Probably averaging 100 nights per year. I have never once shared a room. My rule in travel was always, "the same as home or better".
I don't share at home, so I wouldn't for business.

And she can get a cpap machine

Was going to say this about sleep apnoea, it's a recognised sign and weight loss rarely fixes it.

My CPAP machine doesn't disturb DH, they are fairly quiet, just a bit scary when you see someone in a mask, I've even scared myself sometimes

OP just say you felt very uncomfortable and although you happened to be good friends (in and outside work) with your previous colleague and therefore out of good will you agreed to share, there is now no colleague you are close enough to.
Everyone else on this thread of course it isnt a health and safety or safeguarding risk to ask two known colleagues of the same sex to share a room! Uncomfortable yes. Professional - definitely questionable. Safeguarding issue? Ridiculous suggestion.
And to add to the other teachers on this thread, you are all so up in arms at the thought of workplaces asking colleagues to roomshare, so I really hope you don't also expect residential trips for your children and if you do, that you expect and are happy to pay extra for staff to get their own rooms because I assure you we don't (we also don't get overtime, downtime, personal time, a full night's sleep or privacy by the way despite it being our job).

A couple of years ago DH and I were checking into a hotel behind a a guy. He was there for work and was booked to share a room with someone from the same company but who he'd never met before.
DH and I looked at each other like 😳
Not a chance....

The snoring may be sleep apnoea. Weight loss doesn't often fix it (though it's touted in our fat phobic society as a fix). The things that work are CPAP machines and sometimes surgery (adenoids etc) and sometimes mouth guard type devices that hold the jaws in particular positions.

Do you have a relationship with her that would allow you to suggest she visits her GP to ask for a referral for a sleep study?

The poor snoring person needs her own room - either to use a CPAP machine without disturbing anyone else or because her snoring is just snoring that shouldn't be distracting someone else's rest.

You could consider asking the company to book an Airbnb style place with separate bedrooms if that works out cheaper than two hotel rooms.

Ask if you can book an airbnb with 2 bedrooms or 1 bedroom ND a sofe bed in the lounge. My friends and I do this all the time. It's def cheaper than 2 rooms at a hotel, so that might be better. And best still, no room service.

Tell your manager you and new colleague are incompatible and will not be able to room share in the future, Be firm and professional, there is no need to embarrass your colleague (or yourself) by mentioning why. If your manager pushes it take it to HR.

it's unreasonable that your company expect you to share with anyone. I used to travel a lot for work and single rooms was just standard.

It's nothing to do with weight here. My ex snores and drove me up the wall. He wasn't over weight.

No way would I put up with sharing a room for work. Not. Happening. However you gave it a shot and your new colleague makes proper sleep impossible - I would 100% refuse to do it again. Can’t believe how cheeky your company is expecting this in the first place.

I would wait until you are approached to go away again then ask if you can share - if that is all that is offered with someone else . I would politely say we are so different with a knowing smile. I would want to protect my job and not be known for being awkward which is what can easily happen . Its not what you say but how you say it. I would say the minimum apart from it made you feel uncomfortable but stress you wouldn't want to go into detail .

I'd go to my manager, or call them, "Bob, Sally was snoring all night and I couldn't sleep, so I'm going back to sleep this morning now Sally has gone to work" if they say you can't do that say "well how am I meant to function on no sleep".

You are both adults so should have your own rooms.If they cant pay for 2 then they shouldnt expect you to stay over.They would not expect you to share with a male colleague, so why should they expect you to share with a woman, just to save the company a few quid.Maybe they could downgrade the hotel a star, and still get separate rooms.Or get separate rooms and save costs on food allowance? Unless its a 4 or 5 star hotel £30 seems a lot for just evening meal.Unless thats breakfast as well?

I work for a charity and they certainly would never expect us to share a room with a colleague (we do travel to London twice a year and all get individual rooms) I would absolutely refuse to share a room and they wouldn’t dream of asking us to!

Find a better workplace!

Like fuck would I ever share a room with a colleague, and I've never been asked.

It really is a basic safeguarding issue that you have the privacy of your own hotel room.
Of course I'm not suggesting for a minute that this could be an issue, but I am genuinely stunned at any company thinking they get to enforce this.

I would be emailing and saying I now realise that this arrangement no longer suits me.
I need the privacy of my own room.

Call ACAS to double check but I do not even think this is legally enforceable?

Do it by email, keep it vague, but very firm.
You will not be doing it again.
Any blowback could be deemed grounds for constructive dismissal.

Definitely give ACAS a call.

You are Entitled to accommodation that reflects your home circumstances. But you are NOT a slave. Therefore you should/be entitled to luxury above your means. You are essentially working 24 hours per day. So your remuneration should be assessed as such plus accommodation in excess of your home circumstances. No "ifs" and "buts". Full on recompense as it is for their enhancement, not for yours.

What should have happened;
Sally: gosh Karen I’m excited about the work trip. I do have to warm you though that I snore. Even hubby has a go at me about it as it does keep him awake
Karen: ah thanks for telling me Sally. I think you’re a lovely person but I do need my rest. Are you ok with us going to HR and insisting on separate rooms?
Sally: no absolutely not! That’s exactly why I told you!

what actually happened:
Sally: Gosh Karen I’m excited about the work trip. I do have to warn you though that I snore. Even hubby has a go at me about it as it does keep him awake.
karen: hahahaha (thinking: what a mad cow! Saying snores! Women can’t snore) hahaha Karen good one!
(during the trip)
Karen: (thinking) bloody hell she does snore! I thought she was joking as surely women can’t snore. But Jesus she snores like a man. And she is fat. Whaaat?? Room service? No wonder she’s fat. Phoning her husband AGAIN? Does she have to? She could have warned me she snores. I can’t sleep. She snores. The room stinks. She’s phoning her husband…. This is awful. I need my privacy’s why did she not spell it out that she snores??

The cost of a hotel room for an employee traveling for business is generally a tax-deductible expense for the company, provided the travel is solely for business purposes. The expense must be incurred "wholly and exclusively" for work, typically excluding personal leisure days. So in this instance the company is not saving money by asking employees to share - its just an illusion. I would be reminding them of that.

Teachers are always expected to share rooms. I’ve stopped volunteering on trips for this reason.