<html><head><style type="text/css"><!-- DIV {margin:0px;} --></style></head><body><div style="font-family:times new roman,new york,times,serif;font-size:12pt"><div style="font-family: times new roman,new york,times,serif; font-size: 12pt;">Dear All,<br>I am very thankful for the discovery of this forum. You are truly passionate and anybody can learn a lot from all of you.<br>I will start building a strawbale house near Bucharest - Romania next year in may and as you can see in the attachment I have osb on the interior for structural reason and the easiness of execution. My question is: It is possible or NOT to plaster OSB with lime mortar on reed blanket? Anybody do that? Any tips and tricks? <br>Respectfully yours,<br>Alex Cristescu <br><div style="font-family: arial,helvetica,sans-serif; font-size: 13px;"><font face="Tahoma" size="2"><hr size="1"><b><span style="font-weight: bold;">From:</span></b> asbn
<asbn@baubiologie...><br><b><span style="font-weight: bold;">To:</span></b> European strawbale building discussions <strawbale@amper....muni.cz><br><b><span style="font-weight: bold;">Sent:</span></b> Wed, December 1, 2010 11:08:13 PM<br><b><span style="font-weight: bold;">Subject:</span></b> Re: [Strawbale] OSB or Not?<br></font><br>
Dear Michel, Jure and...<br><br>Why do you compare a (thick) layer of earth/clay directly affiched/sprayed<br>on strawbales with a (thin) layer of earth/clay on OSB?<br>If this plaster has the same thickness, the thermal mass is the same.<br><br>Let me try to explain, why OSB (or diagonal bracing with wood) is used:<br>a) for the structural strength of the wall, which has to be guaranteed (and<br>is much easier to calculate with the infill-system), otherwise your house<br>would not withstand the windforces and snowloads. You can make diagonal<br>bracing with metal (which is always a problem because of a possible<br>corrosion) or with a structural wood(board) or you can rely on the<br>structural quality of the sandwich-system earth-straw-earth(or lime). But I<br>would not want to explain or proof this to a building official...<br>b) second you need an airproof layer on the inside and a windproof layer on<br>the outside of the wall, especially if you want
to build a low-energy or a<br>passive-house. These layers can be folies under the plaster (which are as<br>OSB nearly impossible to plaster directly without cement) or OSB - this is<br>the great advantage of the OSB-board: it functions as structural board AND<br>airproof layer (Dampfbremse) on the inside of the wall. Airproof in this<br>case means: it guarantees, that your (strawbale) insulation has the full<br>thermal quality and it reduces the moisture going in the wall (from inside).<br><br>We never plaster OSB directly, we use an installation-layer like 3,5 5 cm<br>Heraklith-BM (magnesite-bound), which is similar to Fibralith<br>(cement-bound). This board is an ideal plaster-ground and somewhere you have<br>to put all your installation (heating, water, power) in the wall. Some do<br>that in the straw (I never would do that), some say, they can do it just in<br>separation-walls or floors. I don't believe that.<br><br>So, this is the reason,
why we have these layers: every layer has a function<br>to guarantee the structural (wind, loads), physical (moisture) and thermal<br>(full insulation capacity) of the wall.<br>You can change the materials (like OSB), but you have to find a material,<br>which has the same qualities.<br>I looked long for a subsitution for OSB (in a time, when OSB was not<br>available formaldehyde-free), but only found MgO-boards in China, which have<br>the same quality (but are too expansive if you add the transport).<br>Yes we built with diagonal wood-bracing, folies, reed or Heraklith-BM (as<br>plaster-ground) and earth-plaster in the beginning, but if you calculate the<br>price of the materials AND the work, OSB is much cheaper.<br>We want to build ecological houses in the best possible (ecological and<br>structural) quality to the smallest possible price, this is why we have<br>choosen OSB and Heraklith-BM and strawboards (the Czech ecopanely)
as<br>separation-walls...<br><br>This is - im my opinion - important, if you build for and sell a house to a<br>customer, if you do it for yourself, you can do all these experiments,<br>because you are not capable and can plaster cracks as often as you want.<br>But if you build a house as a carpenter or professional strawbuilder for<br>money, you have to be more careful, otherwise your company will not last<br>very long...<br><br>Mit lieben Grüßen<br>Herbert Gruber<br>-- <br>asbn - austrian strawbale network<br>Österreichisches Netzwerk für Strohballenbau<br>3720 Ravelsbach, Baierdorf 6<br>Email: <a ymailto="mailto:asbn@baubiologie..." href="mailto:asbn@baubiologie...">asbn@baubiologie...</a><br><span><a target="_blank" href="http://www.baubiologie.at">http://www.baubiologie.at</a></span><br><br>> Hello all,<br>> <br>> <br>> As Jure, I am also living in Slovenia and planning a house, and workshop (<br>> together about 500 m2) to
build next summer<br>> I took some time to think about the discussion going on last week about using<br>> OSB.<br>> <br>> <br>> I started off a little different, suggested by this forum, to find a<br>> timber-framer first and then an architect that is used to work with such a<br>> company.<br>> It turns out very good.<br>> Of course, timber framing for strawbale walls is specific, and I will have to<br>> provide the information to the architect.<br>> <br>> My feeling is that using OSB or similar large sheets with strawbale building<br>> can be avoided.<br>> Wouldn't the properties of strawbale walls be better, if just plastered from<br>> both sides?<br>> With a thin plaster on a OSB on the inside of the wall, there is not much<br>> thermal mass either.<br>> <br>> What would be your thoughts on this;<br>> <br>> The framing of the house on the inside is ideal for avoiding thermal
bridges.<br>> On this framing (outside) I could nail thin strips of wood (30mmx15mm) with<br>> spacing of about 50 mm or more, and stag the bales against the strips.<br>> This gives a lateral support to the bales, and some grip for the plaster later<br>> on the inside.<br>> Then sew though the bales and fix the same strips of wood on the outside of<br>> the bales for later good grip of the plaster.<br>> This feels very good, but the plaster becomes maybe too thick (plus burlap or<br>> reed), and is maybe too complicated to do.<br>> <br>> Seen from other buildings, the bales are usually just squeezed between the<br>> poles of the frame.<br>> It looks more simple somehow, but are thermal bridges of the frame and bales<br>> not a problem here, or do the bales insulate enough to avoid troubles?<br>> Windows are also put into "boxes" of sheet material.<br>> What are the ways to avoid thermal bridges here,
condensation of the bales<br>> around windows?<br>> <br>> Now being in the design phase, I would be grateful to get your suggestions and<br>> idea's.<br>> <br>> With greetings from snowy Slovenia!<br>> <br>> Michel.<br>> <br>> <br>> <br>> <br>> <br>> <br>> ____________________________________________________<br>> European strawbale building discussion list<br>> <br>> Send all messages to:<br>> <a ymailto="mailto:Strawbale@amper....muni.cz" href="mailto:Strawbale@amper....muni.cz">Strawbale@amper....muni.cz</a><br>> <br>> Archives, subscription options, etc:<br><span>> <a target="_blank" href="http://amper.ped.muni.cz/mailman/listinfo/strawbale">http://amper.ped.muni.cz/mailman/listinfo/strawbale</a></span><br>> ____________________________________________________<br>> <br>> <br>>
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