Damp in loft conversion - newish house

[jasonlhill]

We purchased this house in December, it's detached around 8 years old - with a loft conversion.

The loft has been split into 4 areas, 1 main converted area down the middle and 3 normal loft spaces around it with doors to access them.

After being here a couple of months in winter, I discovered mould growing on our suitcases (kept in the converted area) and other items, since then it's become a mission to find a resolve for this (if possible).

Currently I have a couple of humidity meters and a dehumidifier running for around 12hrs a day.

At the moment without the dehumidifier running the humidity in the converted area ranges between 60-70%.

The converted area has no ventilation (other than the loft hatch to the side) - I believe this is the main problem.

Based on this information and the picture below - does anyone have any suggestions how I can improve this situation (the dehumidifier is too costly to run daily)

 

[Harry Bloomfield]

Is it a proper, legal loft conversion?

Moisture in the house, will rise and condense out in the colder parts of a house, especially where there is little or no ventilation.

Cooking, baths, and the drying of clothes in the house can make such problems worse.

 

[jasonlhill]

Is it a proper, legal loft conversion?

Moisture in the house, will rise and condense out in the colder parts of a house, especially where there is little or no ventilation.

Cooking, baths, and the drying of clothes in the house can make such problems worse.

From what we know, the conversion was done without a building regulations application.
When we purchased the house we contracted a structural engineer to check the work to ensure it was safe (which it is)

I'm hoping someone might suggest a form of venting somewhere/somehow.

 

[Harry Bloomfield]

When we purchased the house we contracted a structural engineer to check the work to ensure it was safe (which it is)

Safe from collapse, or safe as in to building regulations, with a safe means of escape? I would suggest the prior, if there is also no ventilation...

What sort of stair access is there to the loft?

Lack of building control, suggests it maybe lacks any insulation which will exacerbate condensation up there.

I'm hoping someone might suggest a form of venting somewhere/somehow.

Are there no openable windows, natural light?

 

[freddiemercurystwin]

Is it safe from a fire point of view? As that would effect the validity of your house insurance. You need to check if/how any moisture is entering the unconverted parts and if there is none then add some ventilation if there is none. Do the rooflights in the converted part have trickle vents or is there any other background ventilation? I hope the loft wasn't marketed as a habitable room as without BC approval it should not have been it will forever be an illegal loft conversion.

 

[jasonlhill]

Safe from collapse, or safe as in to building regulations, with a safe means of escape? I would suggest the prior, if there is also no ventilation...

What sort of stair access is there to the loft?

Lack of building control, suggests it maybe lacks any insulation which will exacerbate condensation up there.



Are there no openable windows, natural light?

Structural engineer checked the quality of work for safety. The 'conversion' is not deemed as a room and wasn't sold as a room.

There's no windows and no vents in the converted space.
The left is boarded throughout with insulation underneath.

The 'walls' of the converted part have insulation also around them.

The non converted parts are insulated under the boards with further insulation on top - although what appears to be excess insulation has been dumped in the corner of one loft space - no doubt blocking ventilation there

 

[martygturner]

It is what it is a loft room..not a loft conversion. whilst its a pain the simplest way is to remove the conversion... Roof spaces are designed to have cross air flow to get rid of extra moisture yours has sheets of plasterboard stopping this and these provide a trap for the warm moist air rising up from the house. The main issues will be internal in the converted space as you have found out and the hidden roof area, where the lack of ventilation could be causing unseen moisture to condense against the cold side of the roof.

So how to fix if you want to keep the room...pretty simple add ventilation and heating - I cannot see any from the photos...intrernly add a fan to draw out the moisture eg https://www.screwfix.com/c/heating-...10?extractorfancontroltype=humidistat___timer and make sure the source of the house moisture is kept out..fit a good sealed loft hatch or at least run round the existing one with some foam tape and seal any gaps... controlling the source of moisture is just as important as getting rid of it. Make sure the fan exits to the atmosphere not the hidden roof space. Add a heater an oil filled tube job set to low will keep the temp up so that damp air does not condense before it is extracted.

If you have a bathroom with a shower below any point of the converted room you may want to up the fan rating in terms of air movement in the bathroom.

The hidden roof space can be ventilated ( whilst making sure that there is insulation up the new walls and on the ceiling boards) with some through roof mushroom vents as high up as possible to restore ventilation along the rafters. Insulating this space and sealing out vapour from rising up through the ceiling below can be as easy as laying some polly sheet over the joists. and insulating the over with some blanket.

 

[freddiemercurystwin]

It is what it is a loft room..not a loft conversion. whilst its a pain the simplest way is to remove the conversion... Roof spaces are designed to have cross air flow to get rid of extra moisture yours has sheets of plasterboard stopping this and these provide a trap for the warm moist air rising up from the house.

Assuming it's a pretty conventional developer house the membrane would (should) be a breathable one and as such cross ventilation is not required, at least that's the theory. Generally they work fine however I would look to see if there is moisture getting into the unconverted loft space exacerbating the issue. Just how much mould are we talking about here? If that's a dead end then you'll have to add additional ventilation, there are various ways to achieve this. The converted space requires some background ventilation if there is none.

It looks like what they've done is actually built it within the existing pre-manufactured trusses, hence the odd space.

 

[Harry Bloomfield]

There's no windows and no vents in the converted space.
The left is boarded throughout with insulation underneath.

....and, how do you access that loft space? A proper stair, a loft ladder, or some other means?

Is there a hatch, which could be left normally closed, to prevent the rising moist air entering the space? Then add some ventilation up there, which might help solve your problem.

 

[freddiemercurystwin]

....and, how do you access that loft space? A proper stair, a loft ladder, or some other means?

Now I'm on my PC it looks to me like it's via a hatch/ladder.

 

[Harry Bloomfield]

Now I'm on my PC it looks to me like it's via a hatch/ladder.

Mine is similar, just a bit of an electronics work space, but I fitted a Velux. My rule is to always have the hatch closed in cold weather, but the Velux vent remains open year round. No damp or mould here.

 

[martygturner]

Assuming it's a pretty conventional developer house the membrane would (should) be a breathable one and as such cross ventilation is not required, at least that's the theory. Generally they work fine however I would look to see if there is moisture getting into the unconverted loft space exacerbating the issue. Just how much mould are we talking about here? If that's a dead end then you'll have to add additional ventilation, there are various ways to achieve this. The converted space requires some background ventilation if there is none.

It looks like what they've done is actually built it within the existing pre-manufactured trusses, hence the odd space.

err no roofs are designed to BS5250 with regard to moisture control and require ventilation either eves to ridge cross flow or cross flow between the gables breather membrane is absolutely no substitute.

 

[freddiemercurystwin]

Did that apply 8 years ago?

 

[jasonlhill]

Thank you so much everyone for the feedback so far, will have a read through and consume the information! lol

I appreciate the comments that highlight the issues around the work done to the loft space - personally I'd have done it properly, but that's the previous owners choice unfortunately....

Trying to maintain or resolve the issues is my burden I guess lol

 

[jasonlhill]

So how to fix if you want to keep the room...pretty simple add ventilation and heating - I cannot see any from the photos...intrernly add a fan to draw out the moisture eg https://www.screwfix.com/c/heating-...10?extractorfancontroltype=humidistat___timer and make sure the source of the house moisture is kept out..fit a good sealed loft hatch or at least run round the existing one with some foam tape and seal any gaps... controlling the source of moisture is just as important as getting rid of it. Make sure the fan exits to the atmosphere not the hidden roof space. Add a heater an oil filled tube job set to low will keep the temp up so that damp air does not condense before it is extracted.

If you have a bathroom with a shower below any point of the converted room you may want to up the fan rating in terms of air movement in the bathroom.

The hidden roof space can be ventilated ( whilst making sure that there is insulation up the new walls and on the ceiling boards) with some through roof mushroom vents as high up as possible to restore ventilation along the rafters. Insulating this space and sealing out vapour from rising up through the ceiling below can be as easy as laying some polly sheet over the joists. and insulating the over with some blanket.

Thanks for the detailed response....

There's an electric heater in the loft room, I suspect previous occupier installed it to warm this room during winter months (as there was a tv and chairs)

The loft room runs over the main bathroom and en-suite, both have extractor fans. I used 2 humidity meters to measure changes in humidity in the loft after any of the bathrooms have been used.... the difference is less than 5% increase and this could be coincidence.