New findings on damp foundations.

[Mikael_L]

SP has conducted a study on how mold growth develops on sill plates that have become wet. I realize that I myself need to reassess some opinions I have, not everything dries as well as I thought. :O

http://www-v2.sp.se/publ/user/default.aspx?RapportId=12532#12532
Laboratory study of sill plates and beams exposed to rain
SP Report 2011:18
Author Olsson, Lars
Summary

Our experience from construction site visits is that wooden sill plates are exposed to rainwater if it rains during the assembly time. However, there have been divided opinions in the construction industry about whether it is a problem with regard to the risk of mold growth. The study was conducted to investigate whether wooden sill plates and beams can withstand short-term exposure to water before or during installation and if there is a risk of mold growth occurring.

 

[ordain]

Interesting study.

"In many sampling points with abundant growth, the growth was not visible to the naked eye. This confirms that a microbial analysis is required to reliably determine if the wood is affected by mold growth. In several sampling points, there was sparse growth before water exposure and climate simulation. The wood likely acquired the growth before it was delivered to SP."

If you can't see the growth with the naked eye and the wood might be compromised already upon delivery, even if it looks excellent, that's quite troublesome. How often is microbial analysis conducted on all the wood that's delivered?

But, how "dangerous" is wood with microbial growth that hasn't become visible? How significant is the problem?

 

[Gabbe1]

Is it dangerous to install a sill that has visible mold growth if it has dried out?
The mold growth should stop after the sill has dried, right?

The fact that it can take many months for the sill to dry and that most people don't have time to wait that long is of course a problem.

Can the sill be treated with, for example, wood oil before installation?

 

[Anders_Nilsson]

Soon you will:

1) not be able to build a house yourself without certification
2) only be allowed to build with plasterwood that is coated with fiberglass on both sides

Does anyone recognize this argument from the wet room hysteria from a few years ago (also known as the construction industry's response to bacon fever)?

Seriously, how many houses have been site-built where the timber was rain-drenched during the construction period? Even if you are careful, it's almost impossible to avoid water soaking during the construction period in site-building.

I don't want to sound whiny and I'm not against progress, but this thing with house building feels to me like an already explored area. We have the construction materials and building techniques we need. The cases of sick houses you've read about in the newspapers are usually due to pure idiocy (single-stage sealed facades, too thinly rolled waterproofing, negative slopes, not covering building materials with tarps), not a bit of rainwater.

/Anders

/Anders

 

[gaia]

It does align with what I've heard that wood can withstand getting wet as long as it has a reasonable chance to dry quickly afterwards. Experience shows that building with stone takes time precisely because of the drying times before you can wallpaper and lay floors. Moisture disappears easily when the house has been heated and aired out for a longer period. However, it seems that there is a greater risk of building in damp wood than I thought. You can't see anything once it's built in, and the drying process is more challenging afterwards.

Mold, visible or invisible? The main thing is that it doesn't smell like mold in the house and the wood stays healthy. I sympathize with everyone who built this summer when there weren't long breaks between rain showers and a set moving-in date had to be met.
gaia

 

[gaia]

Seriously, how many houses haven't been built on-site where the lumber has been rain-soaked during the construction period? Even if you are careful, it is almost impossible to avoid water exposure during construction with on-site building.

When building with loose timber, you often take more time so it has a chance to dry

 

[AndersS]

It feels like finding something that has existed for all time without creating problems. Many research reports later turn out to contain flaws, incorrect assumptions, and are not properly conducted. Just take these paint tests that Folksam conducts, and after 6 years on the oldest parts, I now have nothing visible with the paint I use, despite Folksam barely being able to recommend the paint. Now I believe – in many of these tests/research, they do not start from common environments but artificial forms due to time constraints. I recently read a forestry report where, during the 60s-70s, about 150 areas were set aside to handle brush clearing/thinning in different ways to see how growth is affected. Today, almost 40 years later, the results are in. The thickness of the largest trees and the amount of timber are not affected by brush clearing or thinning. However, the forest looks darker and more unkempt when not doing it, and it limits social use, as well as differences in biological diversity, but it doesn’t mean it's worse or better, just different. So how it works in reality and under normal timeframes turns out to differ from simulated tests/research attempting to create "real" environments. We need to dare to use our common sense sometimes and not rely solely on research reports that later turn out to have flaws or even be incorrect.

 

[sblixten]

Interesting.
At least as many new questions as answers.
That thing with mold seems to be one of the biggest problems with houses.
Hope this leads to making progress in the fight against mold.

 

[Mikael_L]

Anders and Anders.
You are absolutely right that one should view this report with skepticism.
No, actually not skepticism, but in the right light at least.

But the important thing is to realize that the mantra builders have murmured for ages:
"It doesn't matter, that will dry up as soon as we get the roof sealed"
must be taken with much more skepticism than before.

I am inserting a few sentences of what Rune Johansson from Byggutbildarna writes in his latest "quick notes"
"Rusting staples, paper curling from moisture. Headache, sticky eyes. That's the situation for the police officers in the police station in Eksjö who now suspect mold in the 1.5-year-old building. The air smells musty. The ground floor is icy cold. Deep puddles have formed in the garage and there is no fresh air, say the police officers in the Eksjö police station. (The era of sick buildings is not over).

At the same time, it is still unclear what has made students and teachers sick at a high school outside Gothenburg that was shut down by the Work Environment Authority just over a week ago. However, almost half of the students have to move to other premises.

At the same time in Tierp, 130 students must be taught in one of the school's buildings that is mold-damaged. A new building is to be constructed, but in the meantime, they have to stay. It is not dangerous, claims an expert, as long as you don't tear into the floors and ceilings!

Meanwhile, a hospital is reported to the Work Environment Authority as a sick building."
quote by Rune Johansson.

This is the situation in Sweden today, 2011.

So what Anders_Nilsson writes "but this business with house building feels to me like a fully explored area. We have the building materials and construction techniques we need. The cases of sick buildings one reads about in the newspapers are usually due to sheer idiocy (single-stage sealed facades, rolled waterproofing too thinly, reverse fall, not covering building materials with tarps), not due to a bit of rainwater."
should probably be assessed in the light that houses are still being erected that from the first day are sick and have problems. Isn't that a serious issue?

 

[AndersS]

I agree with you, but these articles, I think, more show that "research" recommends new construction techniques and then all too quickly get implemented as requirements from Boverket. We must have research, and it is good, but it provides far too few answers on how it works in practice and based on a normal time span that a house should function.

What I "get the impression of" in many cases is that we try to "seal" everything to mechanically solve the problems and achieve minimal energy consumption. I actually believe that newly produced and plastic-sealed houses can give these problems if they become wet during assembly. Even later during usage, with minimal to minor leaks in both outer and inner parts of the house, it can lead to mold problems when you trap the moisture that has occurred. Here, instead, efforts should be made on construction methods that handle moisture better at the core and reduce manufacturing costs for these, so that emergency solutions with plastic sealing currently used as construction methods can be eliminated.

 

[magnu]

Just take these color tests that Folksam performs and where now after 6 years on the oldest parts there is no visible damage with the paint I use, even though Folksam can hardly recommend the paint. Now I think - in many of these tests/researches, they do not start from commonly occurring environments but from artificial forms due to time.

Here, I disagree with you. Sure, the test was designed to accelerate aging, but I believe that if paint A is better than B, then I think A will last longer than B in a gentler environment.

I agree with you, but these articles, I think, show more that "research" recommends new construction techniques which are then implemented as requirements from the National Board of Housing, Building, and Planning too quickly. We need research, and it is good, but it provides too few answers on how it works in practice and from a normal timeframe in which a house should function.

You have a point here; it can be like with space electronics. Space electronics fail due to cosmic radiation and then consume more power. It is not possible to accelerate this by increasing the radiation dose because then the electronics fail in another way.

 

[AndersS]

Or simply that in a gentler environment, say a real environment, neither color A nor B will have problems before it's time to repaint. What I wanted to say, quite unscientifically, is that we are introducing new construction methods that are supposed to be "better" but are not at all tested from a holistic perspective. Of course, also with the drive/lobby from the construction industry that doesn't say no to more expensive construction methods and materials.

 

[gaia]

What I "imagine" in many cases is that we try to "seal up" everything to mechanically solve the problems and achieve minimal energy consumption. I actually believe that newly produced and plastic-wrapped houses can have these issues if they get wet during assembly. Even later during use, with minimal to minor leaks in both the outer and inner parts of the house, it can cause mold problems as moisture becomes trapped. Instead, we should focus on building methods that inherently manage moisture better and reduce manufacturing costs on these so that emergency solutions like plastic wrapping, which is currently used as a building method, can be eliminated.

I agree with you. The goal is to keep moisture out but nothing is done to facilitate the evacuation of moisture that comes in one way or another. Time and again, it shows that this is not the right path to take. There's a good system with air space to keep the outer panel healthy. But what about the rest of the wall? Plastic is used to keep thick insulation dry, and then negative pressure is maintained in the house in case the plastic doesn't seal tightly somewhere... all to protect the insulation and studs from mold. If there's the slightest ongoing moisture load in the insulation and poorly sealed plastic somewhere, it draws mold into the living area. If you're lucky and it's visible, you address it... but otherwise, you might live in a moldy environment for a long time without noticing. You can increase ventilation to dilute the smell, but you'll never get rid of mold spores if it never dries. It feels like the plastic is the most crucial part of the house today . Maybe it’s time to switch from wool to another material with closed air cells that can't store moisture? Or stop using wooden studs in exterior walls?

 

[Mikael_L]

I agree with you. The goal is to keep moisture out but nothing is done to facilitate the evacuation of the moisture that gets in one way or another. Time and again it shows that this is not the right path to take. There is a good system with an air gap to keep the outer panel healthy. But what about the rest of the wall? The plastic is used to keep the thick insulation dry and then the house is kept under negative pressure in case the plastic is not airtight somewhere... all to protect the insulation and studs from mold. If there is the slightest ongoing moisture load in the insulation and the plastic is not tight somewhere, mold is sucked into the living area. If you're lucky that it becomes visible, you address it... but otherwise, you can live in a moldy environment for a long time without noticing it. You can increase ventilation to dilute the smell but you can never get rid of mold spores if it never dries. It feels as though the plastic is the most important part of the house today . Perhaps it's time to switch from wool to another material with closed air cells that cannot store moisture? Or stop using wooden studs in exterior walls?

Yes, then it is probably a change from wooden studs to something else that's needed, right. Because with insulation with closed air cells, the wood and drywall still become mold-infested.

It is never the mineral wool in the wall that molds, but the other material.

 

[Mikael_L]

Since the link in the first post is now broken, I am updating:

https://www.sp.se/sv/training/inter...t_byggande_-_SP_Energiteknik,_Lars_Olsson.pdf

This one is also worth reading:

https://www.sp.se/sv/index/research/woodbuild/publications/Documents/Olsson Bygg o Teknik 5-11.pdf