what size for purlins?


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Old 09-18-09, 05:50 AM
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what size for purlins?

hi, i am putting a pitched roof over my mobile home. my rafters are 2x6, ridge beam is 2x8, collar ties 2x6. because i am using metal panel roofing, i am not putting down any plywood decking. I am installing purlins horizontal to the rafters. what dimensional lumber should i use for the purlins? would 1x4 be enough? the roof is a 6:12 pitch and would not normally be stepped on. -thanks
 
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Old 09-18-09, 11:44 AM
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Before you start in on the project, check with your local bldg. dept. and see if it's legal to put such a cover over the MH. it can't be done in CA.
 
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Old 09-18-09, 12:21 PM
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hi lefty, we all do it here in NH. the permit is already granted with the plans of using 2x6 purlins but everyone in the park is telling me that i am over doing it with those purlins. -thanks. if i use a smaller purlin it will not nulify my permit. our inspector is an "alright guy". he just does not answer his phone! lol.
thanks lefty.
 
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Old 09-18-09, 12:40 PM
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Quite frankly, I really don't care how much of an "alright guy" the inspector is. If you have the permit and an approved set of plans that go with it, you build it the way those plans show!

The inspector has no right and absolutely no AUTHORITY to change (or allow you to change) anything about those plans. His job is to make sure that you follow the plans, as they are approved.

I had an inspector one time who decided to start changing things about the way one of my jobs was being done. Within 15 minutes I was sitting at the desk of the County's Chief Bldg. Official. I never had another problem with that inspector because he was never allowed to do an inspection on any of my jobs!! (I think he was given an alternative -- he could always find another line of work!!)
 
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Old 09-18-09, 02:17 PM
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You use the term "perlins". Are you actually installing perlins between the rafter members? If so, you should use dimension lumber like 2x4. You don't have a nailing surface on the end of a 1x4. Now, if you are strapping the rafters, 1x4 pt is usually used set at 2' intervals (or closer), and you double the first one at the edge of the metal
 
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Old 09-18-09, 02:39 PM
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thanks Chandler, i am strapping the rafters. up here we refer to that process as putting purlins across the tops of rafters. i agree that "strapping" is a much easier term. the building inspector lets us change plans all the time as long as we change within code specs and do not compromise the projects integrity. your suggestion of 1x4 strapping with double up on the edges is exactly what i wanted to do... that lessens the weight for someone working alone substantially. and it does not compromise the integrity of the roof structure. thanks again.
 
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Old 09-18-09, 03:12 PM
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Just remember to walk on the screw heads when you go up your roof. That way, you will always put your weight on the strapping and will have some traction due to the protrusion of the screw head.
 
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Old 09-18-09, 04:57 PM
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Bernard_01,

I'm going to let Larry (Chandler) keep advising you on this one. (He's familiar with the way things are done on the right coast) which is TOTALLY different that how they are on the left coast.

Here, we couldn't put a secondary roof over a manufactured home. The roof of the home itself would have to meet snow and wind loads, as well as being approved for the seismic zone. We couldn't 'site build' a joist and rafter system. It would have to be engineered trusses. And there is simply NO WAY that an inspector could (or would) tell us (or allow us to) to do something other than what the approved plans call for.

(You 'rightie's sure allowed to do some strange things!!)
 
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Old 09-18-09, 05:37 PM
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Yeah, left coast stuff is more stringent, but you have earthquakes and Nancy Pelosi......I didn't mean that. If it were a house, it would be trusses, decking, underlayment, strapping, then the steel, but with MH's, since it already has a "roof", this is considered a supplemental system and can be stick built, not that the original roof has any snow load factors or anything.
 
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Old 09-20-09, 07:49 AM
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you both are right and give great advice. i appreciate you guys being around here!
 
 

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