je suis persuadé qu'il s'agit d'une orthographe incorrecte pour "purlin", panne du toit ou poutre faîtière.

"La panne est une pièce de charpente posée horizontalement sur les fermes. Elle supporte les chevrons. Elle relie les fermes et/ou les pignons et sert de ..."
http://fr.wikipedia.org/wiki/Panne_(charpente) -

"In all metal or mixed building roof systems, purlin members are frequently constructed from cold-formed steel, (or roll formed) C or Z sections. ..."
Gallery Of Sketches - References - See also - External links
http://en.wikipedia.org/wiki/Purlin

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Note added at 17 mins (2010-06-04 13:05:37 GMT)
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"In architecture or structural engineering or building, a purlin (or purline) is a horizontal structural member in a roof. Purlins support the loads from the roof deck or sheathing and are supported by the principal rafters and/or the building walls, steel beams etc. The use of purlins, as opposed to closely spaced rafters, is common in pre-engineered metal building systems and some timber frame construction.

In lightweight timber roof construction under purlins were used to support rafters over longer spans than the rafters alone could span. Under purlins were typically propped off internal walls. For example, an 8"x 4" under purlin would support the center of a row of 6"x 2" rafters that in turn would support 3"x 2" roof purlins to which the roof cladding was fixed.

In traditional timber truss construction purlins rest on the principal rafters of the truss."
http://en.wikipedia.org/wiki/Purlin

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Note added at 19 mins (2010-06-04 13:07:34 GMT)
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Autre exemple de substritution, assez fréquent sur Google:

"I used to frame homes in OK and all the homes I have seen have been pretreated. In fact I do belive it is in the building code(don't quote me I'm not certain). I do know that it would be easy as heck to scam someone into beliving the home has been treated. I'm curious as to where in Oklahoma and who the builders are. When I say the "builders" I am refering to the company over seeing the entire operation(the company the superentendant works for). Also I know quite a few towns have great inspectors, but the majority have lousy ones. This I know from seeing shady work pass on first inspection. I would recomend consulting with someone and seing if they would mind doing a walk-thru and inspecting home throughout the construction. There are alot of things that can cause to BIG headaches and problems in a matter of only 2 years. One major thing that I have seen first hand is bad roof bracing(pearling and pearling braces as well as the blocks that hold the pearlings at a 90 degree angle to the pearling( pearlings hold the roof rafters on center and depending on the pitch of the roof and length of the rafter there may need to be two sets) and the braces should be no more than 4 foot apart if the pearling is 2x6 and no more than 6 ft if it is 2x8...... good luck finding a framer than wants to hang 2x8, and they should be fastened(nailed) very well... and not meaning with a BUNCH of nails) there are many, many other small but important things that go into a home that is made to last. I would be willing to give you contacts that I would recomend for doing a little inspection on your behalf for all the trades involved. Send me a PM and I will get you set up so you get a home not a nightmare in 30 years when the loans paid off."
http://www.catfish1.com/forums/f287/breaking-ground-new-hous...

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Note added at 28 mins (2010-06-04 13:17:02 GMT)
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"so ladies and gents we have the rest of the pearling to do and we'll ... the redneck corruption of the spelling of the actual word; purlin ...</B>"
http://brentroad.com/message_topic.aspx?topic=418422&page=7