Water on extractor fan and shower ceiling.

[jaretti]

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• jaretti
• 9 Oct 2025

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• jaretti
• 9 Oct 2025

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• jaretti
• 9 Oct 2025

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• jaretti
• 9 Oct 2025

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• jaretti
• 9 Oct 2025

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• jaretti
• 9 Oct 2025

Hi all,

Converted office into a shower room. Builder fitted ceiling extractor fan with non-insulated ducting, vents outside through soffit.

Problem is when showering condensation starting to run on walls, water drops formulate on ceiling and additionally pool of water starting to form on rim of extractor fan, which fan trying to suck inside ( which i think is dangerous), as seen on attached video.

I think this fan is too weak and ducting needs to be insulated. Builder is adamant he done everything properly so I think that's falls to me to sort up his mess.

My plan is to buy in-line extarctor fan, something like Manrose MF100T, and a length of insulated flexible ducting. From pictured you can see how ducting goes at the moment. I'm thinking of installing new fan on raised platform to try to have constant rise to the fan and then drop to outside vent. Existing fan max flow rate is 80 m3/h, whether new one would be between 180-245 m3/h, so 2 to 3 times better.

Do you think I'm correct in my assumptions that new set-up might sort out the problem?

 

[Murdochcat]

I wouldn’t bother with insulated ducting. You need a decent in-line fan , mounted higher than the vent pipe out, and keep the vent pipe from the ceiling vent to the fan short.

Also make sure that you have a minimum 6mm gap under the door so the fan can draw dry air into the bathroom

 

[jaretti]

I wouldn’t bother with insulated ducting. You need a decent in-line fan , mounted higher than the vent pipe out, and keep the vent pipe from the ceiling vent to the fan short.

Also make sure that you have a minimum 6mm gap under the door so the fan can draw dry air into the bathroom

Can I ask you why would you not bother with insulating ducting?
In-line spec mention that ducting run should be 500 mm minimum, so would you still disregard it?
How critical is last point? Gap is way too small, but i suppose i can always open the window a bit or in winter leave the door slightly open?
Lastly, is the fan Im thinking of buying is decent enough, in ypur opinion?
Thank you

 

[simplesteve]

The Manrose mentioned above is good for the job, but it’s there to move the damp air out, and replace this void with dry air, keeping your walls etc free from moisture. To do this it needs a good supply of fresh air, hence the gap under the door; it is pretty important.

 

[Murdochcat]

How critical is last point? Gap is way too small, but i suppose i can always open the window a bit or in winter leave the door slightly open?

The last point is VITAL - the last thing you should do is open the window and draw cold moist air into the room. In fact if that's what you are doing currently, it could be the reason for so much damp.

I've fitted hundreds of fans over the years and I know what works, and what causes problems

 

[jaretti]

Hi all.

Trimmed the door in the shower room so it's around 20mm gap, little to no improvement.

Wrapped flexi ducting with Thermawrap and also insulated it further by covering it with loft insulation - made it worse, water started to collect on the fan much sooner now.

I'm at my wits end now, don't know if the ducting is getting squashed somewhere, or it wasn't installed properly in the first place. The fgact that access is so bad, you have to crouch at the same time as trying to maneuvre as not to damage ceiling...

 

[foxhole]

You need the inline fan, have you checked outlet is unobstructed .?
It’s also essential the fan has a timer run on and is used at every bathroom use .
You hose layout is poor as it all runs back to fan , it should be vertical till its higher than the exit so run back of condensation is minimised.

 

[jaretti]

Outlet seems ok, air blowing out of it.
I agree about hose layout, but because where builder made a hole in the wall highest point is in that wall, not sure how I could improve it...