I'm considering purchasing a house built with blåbetong. The seller has taken a measurement, but it was done over just one day! Is it of any value at all? The measurement showed 100 and 73Bq/m3 on the upper and lower floors, respectively. The reason for the radon measurement was that gamma radiation from the outer walls and mainly the inner walls exceeded 0.3microS/h, with a peak at 0.47microS/h. So my question is, is the radon measurement reliable at all? Or should it only be seen as an indication? Both outer and inner walls are made of blåbetong. Could the floor structures also be made of blåbetong?
The gamma measurement is worth what it indicates. It can perhaps be seen as an indication. Radon, on the other hand, must be measured for 70(?) days during the winter months indoors when you don't air out as much.
Gamma values below 0.3, I believe, touch on the approved values for new construction today.
I don't think the joists can be made of blåbetong, no. It is not as tough as regular concrete.
Gamma values below 0.3, I believe, touch on the approved values for new construction today.
I don't think the joists can be made of blåbetong, no. It is not as tough as regular concrete.
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Spoke with the realtor today and according to them, the joists are cast arches and may contain blåbetong. I can add that the realtor did not seem particularly certain.
Of course he's not sure... He's a real estate agent. If he said it was one way or the other, he'd have to stand by it. It might be good to have a floor plan of the house? Maybe he can arrange that? I don't have much regard for real estate agents as you can tell... As I said, a floor plan would probably be good.
Floor structures containing blue lightweight concrete occur and are not so uncommon (unfortunately). Radon measurements are essentially worthless, partly because the measurement period is too short, partly due to the wrong time of year, but primarily because there is no information about how and by whom they are conducted! A short-term measurement can be used as an indication if it is done under the right conditions, but the results above sound unlikely, they are too low compared to what one should expect under those conditions...
The results may indeed be accurate, but you cannot know for sure. Blue concrete was manufactured in several different places in Sweden back in the day. In Västergötland, around Gävle, in Skåne, and for example on Öland. It contains alum shale that was collected in these areas. Depending on WHERE the alum shale comes from, the blue concrete has varying levels of radon. The one from Öland (I've heard) is supposed to be practically free of radon. Since I myself live in a blue concrete house, I have tried to check up a bit. Thankfully, we got very low excellent values. It could be Öland concrete... The gamma measurement gives a correct result immediately, as mentioned. That might be seen as an indication of where things are leaning.Humulus said:
I did not write that it was impossible for the measured values to be correct - rather, based on experience with quite a few objects, I find it unlikely that the values are representative of the annual average in the building in question! It's entirely correct that the content of uranium shale varies between the different manufacturing locations (and thereby a corresponding difference in the amount of Radon gas emitted), and there are certain differences even in different batches from the same manufacturing location, although with less variation. The measured values of gamma radiation suggest it's not from one of the worst manufacturers, but are higher than what is usually found from Granhögen (Öland). It should also be noted that there is often a mix-up between the blue lightweight concrete produced in Öland and the white, sand-based lightweight concrete also manufactured there, which in principle does not emit any Radon at all.
oskis 123 said:
Posting all the measurements of gamma radiation here so you can see better. You seem to have a good grasp on this.
Ground floor:
inner walls 0.20-0.32 microSv/h
outer walls 0.22-0.47 microSv/h
Upper floor:
inner walls 0.20-0.27 microSv/h
outer walls 0.23-0.33 microSv/h
Basement:
inner walls 0.12-0.13 microSv/h
outer walls 0.10-0.24 microSv/h
As you can see, I stated the highest measured values in a previous post. Not sure if this was done correctly or if these numbers give a more accurate picture?
Ground floor:
inner walls 0.20-0.32 microSv/h
outer walls 0.22-0.47 microSv/h
Upper floor:
inner walls 0.20-0.27 microSv/h
outer walls 0.23-0.33 microSv/h
Basement:
inner walls 0.12-0.13 microSv/h
outer walls 0.10-0.24 microSv/h
As you can see, I stated the highest measured values in a previous post. Not sure if this was done correctly or if these numbers give a more accurate picture?