Help - Attic Condensation Issues

[RFS]

I was faced with the same situation: large space in the loft but all the problems that it has. Decided to invest for my retirement and had a specialist conversion that changed this ...

 

 

... into this

 

 

 

This was about 10 years ago now. Headroom is just over 6ft which is fine for me. It can still get hot in the summer being the highest point in the house, but the windows can be opened. The right-hand side is a bit low for a scenic section but is fine for the storage yards as this early picture shows..

 

 

 

[RobinofLoxley]

I am tempted to disagree with Mr Bacon but I'm no specialist in the area. Simply allowing in house air to the loft , which is normally pretty dry especially during the winter when central heating is on, should not produce condensation on that scale.

 

I have had a loft layout in a 30 year old house, for the last 5 years, then when the house was new, for the same length of time. I installed loft boarding according to the recs of the time, not the whole space, particularly respecting the  requirement for ventilation at the eaves. Ventilation just means movement of air, not a howling gale. It would be too cold on a day like today although if I ran the fan heater for a few hours I could be up there now. It will be about 8C now, 13-14C with the fan. In summer it gets to 40C at head height under the eaves, which I can bring to 25C with the cooler, but generally I dont go up there when the sun has been shining all day.

 

Despite much comment to the contrary I have had no trouble with rail expansion - I left good gaps and understand thermal expansion in practice. The only thing I have noticed is that all the locos run better in summer when the temps are up, but that was the previous layout that was DC with droppers only used for sidings and other switched isolations. Plenty of simple physics to explain that.

 

I suppose that I only started using the loft as the conditions seemed reasonable in the first place - if I had any doubts at the start a 50% garage conversion was also possible. So we used it on a test basis at first, no problems, use continued....

 

Strictly re Robert's post above, I hope that you are well insured, and that a structural engineer has certified the work.

[F-UnitMad]

1 hour ago, RobinofLoxley said:

Simply allowing in house air to the loft , which is normally pretty dry especially during the winter when central heating is on, should not produce condensation on that scale.

I agree with that (again, being no expert). The scale of the 'indoor rain' in the OP's photos is worse than I get in the un-insulated, unheated steel shed I have at the top of my garden - used as a tool shed & workshop. No trains are up there nowadays. My 1930's Semi loft space never ran with condensation like that even when it was in it's 'as built' state - almost just slates & rafters & a thin layer of insulation. For a house just a year old, that level of condensation looks awful - if I read the OP right, he wasn't up there for some time just prior to taking the photos, and there is no way all that moisture came just from his breath or a waft of warm air up the hatch.

[chris p bacon]

2 hours ago, RobinofLoxley said:

I am tempted to disagree with Mr Bacon but I'm no specialist in the area. Simply allowing in house air to the loft , which is normally pretty dry especially during the winter when central heating is on, should not produce condensation on that scale.

 

I can assure that the air in your house when the heating is on has as much moisture as any other time of the year, The moisture you see in the OP's loft is from peoples breath as well as vapour carried in warm air. As soon as it hits the underside of the roofing felt it condenses. 

Loft voids are built as cold or warm, there is either 100mm of wool inbetween the trusses and 170mm laid at 90 degrees (270mm total) or there is foam board insulation laid over the rafters. The OP's loft is cold.

 

1 hour ago, F-UnitMad said:

I agree with that (again, being no expert). The scale of the 'indoor rain' in the OP's photos is worse than I get in the un-insulated, unheated steel shed I have at the top of my garden -

How many people, kitchens, bathrooms, toilets producing vapour do you have in the shed ?

 

1 hour ago, F-UnitMad said:

 My 1930's Semi loft space never ran with condensation like that even when it was in it's 'as built' state - almost just slates & rafters & a thin layer of insulation. 

 

The thin layer of insulation meant that excess heat went up into your loft space and warmed the underside of the roof, this cuts down the amount of condensation.

 

Lofts and their use come up time after time and I thought about putting together some information on the pitfalls of using an uninsulated and structurally unsound part of the house for a MR.  But I realised that whenever lofts are discussed no one takes a blind bit of notice of anyone with any experience and I would've ended up putting a brick through the screen. 

[john new]

The big problem with modern lofts is that they are not designed and built for what people actually want to use them for, and probably haven't been since the 1960s. From a users perspective they should be built like attics used to be, i.e. suitable for general storage areas or as studio rooms like the old maid servant quarters.

 

I guess economics to keep building costs down is the reason that sea-change happened but W frame lofts that you can't use to store stuff in are just plain wrong. The house I live in now is a 1973/4 build, with a loft comprising useless dead space. If we ever move again I will definitely be trying to avoid the latest build standards as they look even worse. Not sure I fancy moving into a wooden hut, that has been outside in the rain, and then having outside cladding added, that type is all that seems to be being built round here.

 

 

Edited January 5, 2021 by john new

[Paul_C]

John,

 

Read with interest your post. I will PM you on Wednesday.

 

Paul C.

[Stevie]

I think a clarification on words used is required In modern new housing, as in roof void, not attic or loft.

Modern roof trusses are not designed for storage loads.

 

regards

 

[SM42]

14 hours ago, RobinofLoxley said:

I am tempted to disagree with Mr Bacon but I'm no specialist in the area. Simply allowing in house air to the loft , which is normally pretty dry especially during the winter when central heating is on, should not produce condensation on that scale.

 

 

 

 

 

Don't forget that the warmer the air, the more moisture it can hold.

 

Now I'm no physicist  and my understanding of things like humidity is limited  but a quick internet search shows:

 

At around 5 celsius (not unreasonable in a loft currently) saturated air can hold around 6-7g of water / cubic metre.

 

At 20c, (a pleasant indoor temperature,)  saturated air can hold around 2 - 3 times more, 17-18g of water / cubic metre.

 

In a totally unscientific leap of simplification, consider you  now  add your warm wet 20c air to the dryer 5c air and the cold surfaces in the roof and it will cool losing its ability to hold moisture.  That 10 grams of water per cubic metre has to go somewhere. 

 

Andy

Edited January 5, 2021 by SM42

[spikey]

6 hours ago, chris p bacon said:

... But I realised that whenever lofts are discussed no one takes a blind bit of notice of anyone with any experience and I would've ended up putting a brick through the screen. 

 

And who could have blamed you?  

[Enterprisingwestern]

 

If anyone would like to come and study a prime example of how not to build houses/garages with the intention of not allowing mould and damp to become rampant, then I offer you a visit to my humble Spanish abode.

The atrocious/non existent Spanish building regulations are a salutary reminder of how lucky you are in the UK to have decent building standards in the first place, and the facilities/equipment/tradesmen/solutions to solve any problems.

 

Mike.

[teaky]

10 hours ago, RobinofLoxley said:

I am tempted to disagree with Mr Bacon but I'm no specialist in the area. Simply allowing in house air to the loft , which is normally pretty dry especially during the winter when central heating is on, should not produce condensation on that scale.

 

I have had a loft layout in a 30 year old house, for the last 5 years, then when the house was new, for the same length of time. I installed loft boarding according to the recs of the time, not the whole space, particularly respecting the  requirement for ventilation at the eaves. Ventilation just means movement of air, not a howling gale. It would be too cold on a day like today although if I ran the fan heater for a few hours I could be up there now. It will be about 8C now, 13-14C with the fan. In summer it gets to 40C at head height under the eaves, which I can bring to 25C with the cooler, but generally I dont go up there when the sun has been shining all day.

 

Despite much comment to the contrary I have had no trouble with rail expansion - I left good gaps and understand thermal expansion in practice. The only thing I have noticed is that all the locos run better in summer when the temps are up, but that was the previous layout that was DC with droppers only used for sidings and other switched isolations. Plenty of simple physics to explain that.

 

I suppose that I only started using the loft as the conditions seemed reasonable in the first place - if I had any doubts at the start a 50% garage conversion was also possible. So we used it on a test basis at first, no problems, use continued....

 

Strictly re Robert's post above, I hope that you are well insured, and that a structural engineer has certified the work.

I'm not sure which Robert you are referring to but in case you mean me then yes, I used a structural engineer and all work was inspected and certified by Building Control.  I spoke to our insurer and there was no additional cost.

 

I am firmly in the camp of only using a loft space for storage unless it has been properly modified to make it structurally sound, safe in a fire and energy efficient.  Not only is it the most expensive asset I own but there is no way I would compromise the safety of my family.

 

[Richard_A]

I'm not sure how much people understand about extra loading on roof trusses and ceiling ties/joists. 

 

My civil engineering lecturer who is has written the span tables for floor joists /roof members etc explained that they can sometimes be designed to have a much smaller safety margin than an equivalent roof structure,  a properly designed floor is designed to take loadings of 1.5kN/150kg per m2 whereas a ceiling is only designed for 0.25kN/25kg per m2, it really is not worth the risk to load up loft floor joists or roof truss members any more than there designed load capacity. 

[gordon s]

Just going back to the OP, I’m still not sure if there is any insulation between the ceiling joists in the loft. Apologies if I missed it.

 

I cannot believe in these days of climate change and demands for top quality insulation in houses that a one year old property has such condensation issues. Whether the design is hot or cold, surely there must be an insulation barrier somewhere in the design. 
 

Having had a garage conversion with five RSJ’s added to take the weight, I’m firmly in the professional conversion camp, but of course understand the cost implications and the temptations of such a large space for a layout. 

Perhaps if I could make the decision again, I would have gone for a loft conversion rather than a garage, but what’s done is done.  6m x 6m seemed a huge space at the time........

[Enterprisingwestern]

30 minutes ago, gordon s said:

surely there must be an insulation barrier somewhere in the design. 
 

 

I think it's generally called the loft hatch.

 

Mike.

[Harlequin]

1 hour ago, gordon s said:

Just going back to the OP, I’m still not sure if there is any insulation between the ceiling joists in the loft. Apologies if I missed it.

 

I cannot believe in these days of climate change and demands for top quality insulation in houses that a one year old property has such condensation issues. Whether the design is hot or cold, surely there must be an insulation barrier somewhere in the design. 
 

 

29 minutes ago, Enterprisingwestern said:

 

I think it's generally called the loft hatch.

 

Mike.

 

I think Gordon means an insulation layer somewhere between the warm habitable rooms and the outside.

 

I think you can see rockwool between the "joists" in the OP's first photo - so the expected insulation layer is present.

 

We can't really know why the OP has that level of condensation because we don't have all the info. He needs to get professional advice from someone who can perform a site visit.

 

And talking of climate change: When I said above that heating or dehumidifying (or cooling) an uninsulated space is unsustainable I could have said, irresponsible...!

 

[gordon s]

I looked at that pic numerous times and wasn't sure if that was Rockwool or not. If it is the case and it's of sufficient thickness (4"- 6") and it's not blocking the vents at the sides, it should prevent heat entering the loft space. The only way then for heat to enter the loft space would be via an open loft hatch. Still finding that hard to believe as our loft is dry as a bone and we have the rock wool insulation plus an access hatch.

 

When I was putting up new lighting, the hatch was open for hours and we still didn't have condensation of any level, even with the heating going full tilt.....My wife has a blind spot with a thermostat.....

 

There's clearly something wrong that needs further investigation.

[F-UnitMad]

12 hours ago, chris p bacon said:

13 hours ago, F-UnitMad said:

I agree with that (again, being no expert). The scale of the 'indoor rain' in the OP's photos is worse than I get in the un-insulated, unheated steel shed I have at the top of my garden -

How many people, kitchens, bathrooms, toilets producing vapour do you have in the shed ?

 

13 hours ago, F-UnitMad said:

 My 1930's Semi loft space never ran with condensation like that even when it was in it's 'as built' state - almost just slates & rafters & a thin layer of insulation. 

 

The thin layer of insulation meant that excess heat went up into your loft space and warmed the underside of the roof, this cuts down the amount of condensation.

My shed is steel sheet, that warms up rapidly in sunlight, hitting the cold air in the shed - I'm not surprised at the amount of condensation in there during the winter months!!!

Roof slates can get very hot in sunlight too; my loft as I said used to have a thin (and by then old & worn out) layer of insulation in there, but even when I put in new, thick insulation to keep the heat in the house & the loft cold, it didn't cause condensation like the OP's when the sun hit the slates - and there was no tar paper or whatever under them. Built in 1936; I bought the house in 1998 & put the new insulation down a couple of years later.

 

I'm not advocating using the OP's space un-converted, by any means, or nay-saying what should be done to a loft to make it useable - I'm just amazed at the amount of condensation in there that cannot be good for the house at all.

Edited January 5, 2021 by F-UnitMad
Spelling, fat finger syndrome just as RMweb went on a go-slow...

[Phil Himsworth]

9 hours ago, Stevie said:

Modern roof trusses are not designed for storage loads.

Curiously I saw a crane being used to install some trusses on a new build the other day and they had an extra horizontal timber across the centre section of the truss a short distance above the bottom timber; about the distance that would be required to lay boards down above a foot or so of insulation.

 

It struck me as a good idea; if people are going to want to board out some of their loft it would make sense if the supporting structure was already part of the truss rather than something added afterwards.

[chris p bacon]

1 hour ago, F-UnitMad said:

but even when I put in new, thick insulation to keep the heat in the house & the loft cold, it didn't cause condensation like the OP's when the sun hit the slates - and there was no tar paper or whatever under them. Built in 1936; I bought tge house in 1998 & put the new insulatikn down a couple of years later.

And there is the reason why, without any underfelt your roof was venting freely and any moisture on the underside of a slate is carried down onto the one below.

 

For info the current spec for between joist insulation is 250mm-  270mm (11"), if the OP has disturbed the insulation and reduced it's thickness while installing boards etc this will contribute to the problems.

[spikey]

Perhaps I missed it, but has the OP been back to this thread with his comments?

[RobinofLoxley]

5 hours ago, Enterprisingwestern said:

 

If anyone would like to come and study a prime example of how not to build houses/garages with the intention of not allowing mould and damp to become rampant, then I offer you a visit to my humble Spanish abode.

The atrocious/non existent Spanish building regulations are a salutary reminder of how lucky you are in the UK to have decent building standards in the first place, and the facilities/equipment/tradesmen/solutions to solve any problems.

 

Mike.

That is extremely debatable. You should follow the progress of the Grenfell enquiry

[RobinofLoxley]

4 hours ago, gordon s said:

Just going back to the OP, I’m still not sure if there is any insulation between the ceiling joists in the loft. Apologies if I missed it.

 

I cannot believe in these days of climate change and demands for top quality insulation in houses that a one year old property has such condensation issues. Whether the design is hot or cold, surely there must be an insulation barrier somewhere in the design. 
 

Having had a garage conversion with five RSJ’s added to take the weight, I’m firmly in the professional conversion camp, but of course understand the cost implications and the temptations of such a large space for a layout. 

Perhaps if I could make the decision again, I would have gone for a loft conversion rather than a garage, but what’s done is done.  6m x 6m seemed a huge space at the time........

I have the impression that UK housebuilding regs are actually not fit for purpose and are generationally overdue for an update. Yet just think, prior to Grenfell a committe of MP's were meeting to discuss how to remove existing building regs

[RobinofLoxley]

5 hours ago, teaky said:

I'm not sure which Robert you are referring to but in case you mean me then yes, I used a structural engineer and all work was inspected and certified by Building Control.  I spoke to our insurer and there was no additional cost.

 

I am firmly in the camp of only using a loft space for storage unless it has been properly modified to make it structurally sound, safe in a fire and energy efficient.  Not only is it the most expensive asset I own but there is no way I would compromise the safety of my family.

 

Im relieved about that. I didnt know whether to say anything but many times people stay silent when they should speak, in many walks of life. I know someone personally who went down the same route as yourself wthout checking and its nearly cost him his house

[RobinofLoxley]

4 hours ago, Harlequin said:

 

 

I think Gordon means an insulation layer somewhere between the warm habitable rooms and the outside.

 

I think you can see rockwool between the "joists" in the OP's first photo - so the expected insulation layer is present.

 

We can't really know why the OP has that level of condensation because we don't have all the info. He needs to get professional advice from someone who can perform a site visit.

 

And talking of climate change: When I said above that heating or dehumidifying (or cooling) an uninsulated space is unsustainable I could have said, irresponsible...!

 

Dont, unless your own world is completely perfect.