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T&G pine on purlins?

Started by Rjwassink67, March 13, 2019, 01:47:15 PM

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Rjwassink67

For my ceiling, I plane to use T&G pine on my purlins.

1.  Won't dirt/debris work its way through the grooves as it moves around from swelling and shrinking or is this not a problem?   Should I cover the top of it with drywall or some other product?

2.  How far can 1x6 T&G go unsupported without sagging? 3', 4', 5', more?  There will be fiberglass insulation and some can lights on this as well as additional weight.

I will have independent trusses above the ceiling supporting the roof, so the timber frame will be

  a stand alone system.

Thank you!

Mike W

Rjwassink67,

If you are concerned with dirt / debris migrating through the T&G during normal movement, you could always install a vapor barrier such as Tyvek or Felt to build a dust barrier below the insulation on the purlins prior to the T&G installation.  Whatever you decide ensure if there is moisture barrier on the upper section of the roof structure you use a breathable material such as Tyvek or other to prevent encapsulating the area which would cause any latent moisture to grow mold, the envelope needs to breath.  Best is eave and ridge venting to allow the hotter days / cooler nights to have their way with the envelope and yet can out gas any condensation buildup. 

as for the T&G 1x6 no problem spanning the 5' distance as the T&G are self supported along each edge at 6" intervals the entire length of the run, it builds a diaphragm of sorts, just without shear properties, your roofing sheathing will accomplish the shear needed of the roof structure.

The insulation and light cans will not hinder the above statement.

Mike

Don P

An air barrier is the biggest thing with T&G to keep air from moving through it. Can lights are typically a chimney through that air barrier you can often drive through neighborhoods on frosty mornings and spot the unfrosted areas above can lights.

I'm curious about the order of construction here?

Rjwassink67

Quote from: Don P on March 13, 2019, 10:08:46 PM
An air barrier is the biggest thing with T&G to keep air from moving through it. Can lights are typically a chimney through that air barrier you can often drive through neighborhoods on frosty mornings and spot the unfrosted areas above can lights.

I'm curious about the order of construction here?
Funny you should mention the order of construction, I'm also thinking about that as well!  Right now: timber frame, trusses, roof (to dry in as soon as possible), T&G - just slide them in from the sides, if I do drywall (but I like the tyvek idea) slide the sheets between the purlins as we go.  This is will be a tight fit between the timber frame and trusses but should be ok.  My bents are 10' on center and I may go 5' on center for the purlins.  So i will be able to take a full sheet up flat.
So I should place the tyvek printed side against the T&G?  This will slow air movement, but would it trap moister against the T&G?

Ruffgear

Seems like an odd way to do things to me. Is your timber frame not structural? If not, why not put t&g to bottom of rafters and put faux timber frame on inside?

Rjwassink67

My timber frame will not be structural.  I want the room above in the trusses for insulation.  I also don't want the really high cathedral ceiling to save on heating area. I need/want the pitch of the roof for our snow load.  I have never liked the look of faux timber frame.  They rarely look great.  I would put the T&G on the rafters and my trusses up against it, but I was instructed on this forum to NEVER attach the timber frame to the trusses.  This is the reasoning behind my different approach.  If I'm way off on my thinking I would love to hear the responses.  Thanks all

flyingparks

Have you thought about SIPs? May be a good option in your case. Timber Frame, T&G, SIP, Ice and Water Shield, Roofing. Next to bullet proof

Rjwassink67

I don't want the high cathedral ceiling that I would end up with if I used SIPS.

flyingparks

Then I'm confused by your drawing. But reading previous posts you said that your timber frame I non-structural. So are your structural trusses going to be a steeper pitch?

Rjwassink67

Yes, the trusses will be steeper.  I don't know the numbers yet, but maybe 9/12 outside and 6/12 inside pitch in the scissor truss.  The timber frame would be designed to just fit inside, maybe 5.5/12.

Hilltop366

How about timber frame then T&G boards then vapour barrier then a layer of foam board or two then trusses and more insulation between trusses? The layer of foam board will really help with thermal bridging through the trusses and condensation on the vapour barrier.

With all this new LED lighting there is probably a light fixture that you can install on the ceiling in a pancake box that depending on the thickness may not even go through the T&G, this may be a better option.

Don P

As long as the truss designer knows where the bearing is I would question the NEVER.

If the spans can be handled by stick framing I would tend towards overframing it with dimensional lumber rafters. Sparky is not gonna be happy.

You could also do scissor trusses in TF with T&G on top of the lower chord.

Ruffgear

As far as the lighting goes. As don mentioned cans can be problematic if not insulated correct. They now have LED that go in standard box and look just like cans. We're seeing a lot of those now.
I now understand your building approach a little better, but I'm still thinking there should be some refining.

Ruffgear

Have you seen tule peaks timbers?

Rjwassink67

Quote from: Ruffgear on March 16, 2019, 10:12:32 AM
Have you seen tule peaks timbers?
Nice!  I will be sawing my own.  

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