Shower leaked through roof

[ineedaholidayandwine]

We moved in to our house 3 months ago, my 5 year old has an en-suite in her room which was built as part of the extension in 2017, we used it once when we moved in, all fine, since then she hasn't used it as wants baths instead.
We're started noticing after a few weeks an eggy smell, put cleaners and sanitizer etc down the toilets and sinks but not her shower as assumed as not used it couldn't be that, i then read about dry pipe so just over a week ago started running a little water through it, this has stopped the smell. Anyway decided she needed to start using the shower so tried it last night, after about 5 minutes husband came up to tell us turn shower off as it was coming through a spotlight in the family room that is underneath the shower (again extension area from 2017 so not old pipes etc), shower off and leak stopped almost immediately.
What could have happened between us using it 3 months ago to now to cause a leak?!
Thankfully no damage to light or ceiling but needs fixing so we can use the shower.

I would look at the shower tray / floor / wall tiles. If they are not properly sealed or behind wall tiles is not properly waterproof this can be a problem - good news - can be easily fixed if that is what it is - but old sealant needs to be taken out completely - just going over it won't properly fix the problem

If she has not used it for 3 months - ( if I have understood ) maybe why the problem was not there or if she has then this is the moment when the problem was just going to arise.

Best wishes to you - been there

How much water was it? If the silicon seals and tiles / panels look okay I'd check the trap/waste if it's accessible under the tray.

Use a watering can to pour a lot of water down it and check the seal for leakage. If it remains dry but you still leak then it's possibly the waste pipework further along.

If neither leak, maybe it's the tiles / silicon or possibly the hot / cold feed to the shower head -- although that's probably unlikely.

Process of elimination. If you have concealed fixtures then it gets interesting.

Everything looks to be properly sealed, accessing the tray would mean removing tiles, hoping then we can access the pipes by removing some of the laminate boards. Husband is wondering if a washer (or similar) in the pipe may have dried out from not using the shower?

My guess is still the waste or waste pipe. Is the leak below the drain hole, can you trace it?

You can't access the underside of your tray to check the waste because it has been concealed in the floor.

Before you pull up the floor or take panels down, try the watering can suggestion or, better still if you have a shower head on a cord point it at -only- the drain for a while and check for leaks leaks below.

If it leaks then it's the trap or waste pipe. In which case it might be easier and cheaper to access it from the ceiling below.

Shower trap seals can fail. Maybe the rubber seal has dried, moved, or it was siliconed with a acetoxy based silicone instead of a nautral silicone. That will rot rubber but it's surprising how many people still use it.

I'll give that a try next week when my husband is around to watch for leaks below.
Accessing via the ceiling below would be a nightmare too as means pulling off the plasterboard etc urgh what a pain!
Pic of ceiling, that is the light the leak came from, i'm not sure if it's directly below the trap but it's certainly not far off

Don't worry too much about taking the ceiling down - part of my kitchen ceiling had to come down a couple of months ago, tracing and fixing the leak took a day and before they left the plumbers cut plasterboard to size and filled the cut gap. Plasterer came next day, decorator a few days later and you'd honestly never know it had happened within a week.

Plus household insurance paid for most of it. Give them a call and see what they cover.

Total pain... but you can remove a small square and repair it with board and a bit of skim. Might need to repaint the whole ceiling, mind.

Before you remove the laminate it could be worth checking which way the joists run and figuring out if there could be one in between the floorboard and trap / waste pipe.

The joys of concealed pipes and wastes... I have several of my own which I think (worry) about more than i should!

Thank you very much, my Fil is good with this kind of thing so going to get him to look when he visits then take it from there. Bloody good job we have other showers!