OSB Board Exterior

[elhenke]

Hello!

I'm working on a small job in a villa construction where the carpenters are installing OSB boards on the exterior. I've never seen it used this way on the exterior before. I haven't mentioned anything to the builder yet because I'm not sure if it's the right approach. But I find it a bit strange. In the drawings I have, it says it should be gypsum. I should add that I can't ask the carpenters because they don't speak Swedish.

 

[Paul-Staffanstorp]

I have also never experienced that, but sure... I'm not a builder either.

However, it sounds very stupid since OSB is quite moisture-sensitive.

 

[MathiasS]

Where in the construction is OSB used on the outside? Like a facade?

Redo it right...

 

[Farzan]

Doesn't it depend on what type of OSB it is?

OSB class 3 and 4 are for "use in humid climates," which is apparently defined as "Regarding class 2 in EN 1995-1-1:2004, which corresponds to a moisture content in the material at a temperature of 20 °C and a relative humidity in the surrounding air that only exceeds 85% a few weeks per year."

It sounds original though, and if I were a contractor, I wouldn't like it when the blueprint specifies gypsum...

Apparently, there is information about it under KEL.1 here: http://ama.byggtjanst.se/CodeTree.aspx?kod=KEL.1&urvalId=19
...if any ladies and gentlemen have login access to AMA's web service!

 

[Johan Gunverth]

A number of years ago, I saw a couple of villas in Lerum that were clad externally with OSB and then plastered. The houses still look very nice.

 

[elhenke]

Have spoken with the contractor now. Apparently, they had discussed this and replaced the gypsum with OSB. It would be some moisture-resistant variant and not the usual one. It had something to do with the fact that the adhesive ability was much better compared to gypsum. Well, I was mostly curious but it seems to be okay to do so anyway. You don't want to just stand by and watch when the customer is being deceived.

 

[Krawk]

Doesn't it depend on what type of OSB it is?

OSB class 3 and 4 are for "use in humid climates," which is apparently defined as "With regard to class 2 in EN 1995-1-1:2004, which corresponds to a moisture content in the material at a temperature of 20 °C and a relative humidity in the surrounding air that only exceeds 85% a few weeks per year."

It sounds original anyway, and if I were a constructor, I wouldn't like it when the drawing says gypsum...

There is apparently info about it under KEL.1 here: [link]
...if any of the ladies and gentlemen have login access to the AMA's web service!

It only contains the text you just quoted and a reference to standards regarding requirements for OSB boards.

 

[Farzan]

OK, thanks for the info, Krawk.

 

[robsarve]

Regular OSB is waxed on the surface and fairly moisture-resistant. I have a simple outdoor storage that was left unpainted for 10 months outdoors, exposed to snow, etc. Other than the sun-exposed sides having grayed a bit, they were like new when I painted them now in October.

 

[Molon]

Seen that in several townhouse-row house areas, the carports are clad with OSB boards in the surface layer and still look great even after 6-7 years.

 

[Kallebo]

Old thread. But it seems that all OSB sold today is class 3 i.e. The variant that can be used "outdoors under roof"..

Was it different 8 years ago or is there a risk that my boards under plastic in the garden will absorb moisture and get ruined?

It rained a bit when I bought them but the water seemed to run off nicely

 

[MathiasS]

I've learned that OSB can be used everywhere:

https://www.google.se/search?q=osb+...ved=0ahUKEwjkt-TmptDNAhXjIJoKHanfCM4Q_AUIBigB

 

[Johan Gunverth]

OSB can be used everywhere I have now learned:

[link]

With emphasis on CAN. 😉

 

[toolman77]

I have built a small "temporary" shed that is OSB-clad and Cuprinol painted.

Now after about 6 temporary years, a couple of OSB splinters have come off, but on the whole, it looks too good for me to bother rebuilding it properly.