Condensation on side extension on ground floor , Pls Help

[sdugoten]

This is a 100+ years old Victoria house and I did a total renovation of the house + side extension in the kitchen. The problem is, we got condensation issue on the ground floor in the kitchen after side extension. We have been battling on this issue for 1+ year. At the beginning, we add a vent on the ground floor ceiling where the water dripping, but as you can see it still have condensation whenever we took hot shower on a cold night. I can see water dripping from the ceiling after shower.

We have been told the problem might be either or both of the issues below

1. The black waste pipe is too close to the white vent tube on the ground floor ceiling. Showering water will flow to the black water pipe and go out of the house. The white vent pipe is the vent for the ground floor toilet fan which go out of the house.

2. The beam that is used by the extension isn't insulated. So the black waste pipe become pretty hot after shower and the beam start condensation.


In order to better illustrate the layout, here is the picture

This is the 1st floor bathroom, the location of the ground floor ceiling where condensation happen

1st floor Bathroom again after the black waste pipe is installed

1st floor Bathroom again, this is after the white vent tube is installed. The white vent tube is used by the ground floor toilet. The ground floor toilet has no window so we use this vent tube to vent the air out of the house. You can see the cold air vent tube is almost next to the hot waste pipe. One suspect is that the condensation happen here after hot shower.

The following picture show where the condensation happen, it's pretty much next to the extension beam. The location of the first picture of the post is the red circle on the right.

 

[sdugoten]

The question is....anyone know how to solve this issue?

We tried to inject gap filler foam (open cell) into the ground floor ceiling to fill the air gap. It did help quite a bit, at least the condensation issue is much much smaller. However, I can still see a few water drop near those 2 red circle in the last pic.

 

[Notch7]

its a bit hard to see the roof construction details of the new extension. As it is a pitched roof, I’m guessing it is tiled.

Is the new roof a cold roof or warm roof?
if cold, how is it ventilated
and if cold what was the detailing insulate the roof where it abuts the house - it’s important to know how it was insulated to prevent thermal bridging.

an external image might be helpful.

are you 100% it’s condensation and not a weeping waste joint or shower cubicle

 

[sdugoten]

its a bit hard to see the roof construction details of the new extension. As it is a pitched roof, I’m guessing it is tiled.

Is the new roof a cold roof or warm roof?
if cold, how is it ventilated
and if cold what was the detailing insulate the roof where it abuts the house - it’s important to know how it was insulated to prevent thermal bridging.

an external image might be helpful.

are you 100% it’s condensation and not a weeping waste joint or shower cubicle

This is only a side extension, which you can see below, only the right side in the picture is extended with pitched roof. It is slate tile.

The condensation happen on both the existing ground floor ceiling, and a bit on the extension ceiling. Basically, water mark next to the black beam. You can also see the white vent tube on the left in the 1st picture. Behind that white tube is the ground floor toilet. The white tube is used by the vent fan in the toilet and then the white tube route to the right on the ceiling and then go across the whole kitchen and the eventually route outside to the garden

Red square = condensation area
Blue square = insulated floor
Green square = extension beam

One thing I noticed is that condensation only happen in the red square area, no other place see water mark along the whole green extension beam. I believe 1st floor insulation in the room did help and only make the area that is not insulated have condensation. Those 2 red spot that have condensation is right below the 1st floor bathroom, and that area is where the black waste pipe and white vent tube is located.

That's why I said there are 2 suspects, either the uninsulated beam, or the hot waste pipe/white cold vent tube are causing the issue. The condensation only happen after hot shower during a cold night below 5 degrees Celsius. We have tested there is no leakage in the water pipe by our builders. As a matter of fact, the water dripping issue only happen in winter, and only happen after hot shower on a cold night.

 

[sdugoten]

extension roof on the left in the picture

This picture is before the extension, the blue area is where the side extension is

 

[SpecialK]

How sure are you that it is condensation rather than a leaking pipe?

For condensation to happen you need humidity with something cold. Your steels are all internal? Why would there be humidity in the floor void?

 

[sdugoten]

How sure are you that it is condensation rather than a leaking pipe?

For condensation to happen you need humidity with something cold. Your steels are all internal? Why would there be humidity in the floor void?

Because there is no water mark at all during summer. These water mark only happen during winter and only happen after hot shower on a cold night.

And we had builder came over and do a water leak test, we first open up the ceiling on ground floor in kitchen to wide open. Then we fill water into the bathtub until full on 1st floor bathroom, and then release the water. We then go downstair and look at the black waste pipe from ground floor. There were no leaking.

The steel beam are all internal, but you see the white vent tube that is next to the steel beam? That white vent tube actually allow air to go out and in from the back garden.

 

[Notch7]

thank you for posting the photos that helps clarify the layout.

Im finding it hard to believe the condensation is due to warm air on the extract pipe -because thats extracting room temperature air to the outside, I presume, so it wont actually be cold, no colder than the air in the ceiling void. Obviously when the extract fan is not on the pipe will drop because the end of the extract is open to the outside albeit with a flap.

given that it only happens on really cold days, It indicates the problem is thermal bridging.
and given the it happens after showering, it seems to me the problem is vapour getting into the floor void

Judging by the pictures the damp is directly below the shower tray, are you totally sure the tray or sealing is not allowing enough moisture into the ceiling void?

I think the only way you will solve this is to cut out the plasterboard under the shower tray…ideally do it when there is water coming through the ceiling a bit, so you’ve something to see. Personally I think you will it damp and mouldy.

 

[sdugoten]

thank you for posting the photos that helps clarify the layout.

Im finding it hard to believe the condensation is due to warm air on the extract pipe -because thats extracting room temperature air to the outside, I presume, so it wont actually be cold, no colder than the air in the ceiling void. Obviously when the extract fan is not on the pipe will drop because the end of the extract is open to the outside albeit with a flap.

given that it only happens on really cold days, It indicates the problem is thermal bridging.
and given the it happens after showering, it seems to me the problem is vapour getting into the floor void

Judging by the pictures the damp is directly below the shower tray, are you totally sure the tray or sealing is not allowing enough moisture into the ceiling void?

I think the only way you will solve this is to cut out the plasterboard under the shower tray…ideally do it when there is water coming through the ceiling a bit, so you’ve something to see. Personally I think you will it damp and mouldy.

The damp location in fact is not directly below the bathtub. (a finished bathroom picture might better explain this) It is in fact under the toilet, around the area in red circle if you see it from ground floor ceiling. The black waste pipe is shared by both the toilet and bathtub I believed.

We did once opened up the ground floor ceiling and see water dripping from the surface of the black and white tube. However, whether the water is the result of condensation of the black/white pipe, or it's somewhere else on the extension beam having condensation and start dripping onto the black/white pipe and then water follow to the pipe lowest point and then drip to the ceiling (which is the red circle area) is unknown.

Toilet on the left and bathtub on the right. Again, we are 100% sure it's not leaking because we have tested many times when we flush the toilet or fill the bathtub with water. Water dripping into ceiling only happen in winter and only after hot shower on cold night. Even a warmer night (10+c Celsius) in winter won't see water dripping.

One thing is that if I turn on heater during night time and keep the kitchen at around 19c Celsius, no water dripping even on a cold night after hot shower.

 

[sdugoten]

Ah..one more thing. When we once opened up the ground floor ceiling in kitchen, we noticed all the area around those 2 red circle in the above picture are all wet. It just happen that the worst area is the location of the red circle and we can see water mark there, but all other area around those 2 spots are wet as well.

 

[Koolpc]

I think you need to open up the ceiling at those points again and leave open to monitor. See what is going on....

 

[Notch7]

Ah..one more thing. When we once opened up the ground floor ceiling in kitchen, we noticed all the area around those 2 red circle in the above picture are all wet. It just happen that the worst area is the location of the red circle and we can see water mark there, but all other area around those 2 spots are wet as well.

to form condensation you need 2 things; a cold surface and warm vapour laden air which then hits the cold surface, where the moisture in the air goes below the dew point and turns to water.

So you need to find those 2 things, so far I’m not seeing any evidence of warm air with a high humidity getting in the ceiling void.

Do you get the problem when draining the bath with hot water?

personally Im struggling to see how hot water from the shower going down the waste and warming would cause condensation, if anything it’s raising the temperature above the dew point.

I suppose it Could be forming condensation on the extract pipe - but where’s the warm , moist air coming from?

are there down lighters in the room below letting moisture in?

could there be an air leak or even tiny water leak from or near the shower tray?

 

[SpecialK]

Do you have backdraught vent on the toilet extract?

Could it be the radiator leaking if it only happens in winter? Do you have a closed loop system?

 

[mrrusty]

but as you can see it still have condensation whenever we took hot shower on a cold night. I can see water dripping from the ceiling after shower.

Like everyone else I just cannot see how enough warm wet bathroom air is going to find a cold enough surface (bearing in mind the hot waste will be warming things up) to create running water.

Is it possible that it's leaking when you have a shower, but on a hot day the drip is drying before it gets to the point it leaks through, and on a cold day it doesn't dry and runs across the ceiling somewhere and drips through? The leak point may be miles away from the drip point. This sounds far more like a leak to me than condensation.

 

[sdugoten]

to form condensation you need 2 things; a cold surface and warm vapour laden air which then hits the cold surface, where the moisture in the air goes below the dew point and turns to water.

So you need to find those 2 things, so far I’m not seeing any evidence of warm air with a high humidity getting in the ceiling void.

Do you get the problem when draining the bath with hot water?

personally Im struggling to see how hot water from the shower going down the waste and warming would cause condensation, if anything it’s raising the temperature above the dew point.

I suppose it Could be forming condensation on the extract pipe - but where’s the warm , moist air coming from?

are there down lighters in the room below letting moisture in?

could there be an air leak or even tiny water leak from or near the shower tray?

Yes, draining the bath with hot water during cold night will result in dripping water on the ceiling in kitchen.

The extract pipe could be very cold because it connect to the garden outside, just a flap at the entrance in the back garden. Since the black waste pipe is literally right next to the white extract tube, would that form condensation water on the white tube when hot water flow thru the black pipe?

Not sure air leak near shower tray. But I don't see water leak because the ceiling should be wet in summer also if there is a water leak . But nothing happen between late Feb to late Oct.