Tag Archives: gambrel pole barn

Eave Height, Gambrel Size, and To Tie New to Old Building

Today the Pole Barn Guru discusses eave height, the size of a gambrel building and advice how to tie new building to existing structure.

DEAR POLE BARN GURU: When you refer to height are you measuring to the peak or sidewall? This pole barn will be used as an indoor (uninsulated) riding arena with some hay storage above. JIM in ADA

DEAR JIM: At least in our case eave height measure refers to sidewalls (https://www.hansenpolebuildings.com/2015/02/eave-height-2/).

Your expectation of being able to store hay above a riding arena is probably unrealistic, both from a standpoint of logistics and investment. Hay is very heavy and in order to carry this imposed extra weight you will multiply roof truss costs significantly. I would recommend finding a place for hay storage on ground level.

Gambrel roof pole barnDEAR POLE BARN GURU: Can you do a 48×48 gambrel style pole, 18-20 ft high? PAMELA in CASPER

DEAR PAMELA: Since my very own home is a 48 foot width post-frame gambrel building with 20 foot high sidewalls I would have to say yes. For practical purposes, we can provide virtually any low-rise building (up to three stories and 40 foot high walls). Your only limitations will be imagination, budget and available space.

 

DEAR POLE BARN GURU: I want to add to my metal building but the addition would require 2 valleys. How do you tie the new roof to the old on a post frame trussed roof. I have done many on a stick building. I have not been able to find any photos or steel parts for this. KURTIS in ROCKFORD

DEAR KURTIS: Your first stop (or call) should be to RDP (Registered Design Professional – architect or engineer) who provided your building’s original design. Structural changes to buildings should always be done under careful guidance of a RDP, especially when it comes to more complex roof designs where accumulations of snow could result in potential failure situations.

Most often a design solution involves removal of any overhangs where attachment will occur. A truss is then added to current sidewall face to support new addition roofline, as well as purlins on edge to create a frame over onto existing roof framing (of course roof steel on this portion of existing building needs to be removed prior to framing). Flatwise 2x framing needs to be added between existing roof purlins – we’ve normally found 2×12 centered upon newly created valley line to work well. This provides both a “landing point” for new purlins as well as backing for steel valley flashing.

 

Insulating an All Wood Gambrel Barn

A reader writes: “Dear Guru.I have an all wood gambrel style pole barn that I’m converting to a shop.  I’ve installed forced air heat and am getting ready to insulate.  My exterior walls are Tyvek wrapped osb and vinyl sided.  I am wanting to use rigid board to help deter rodent nesting.

  My questions are: for the walls should I cut and fit 1 1/2 inch board to fit all of the spaces between my girts before I layer rigid over the girts or can I layer over the girts to start?   The ceiling I was planning on installing 2″ rigid on top of the 2×4 truss bases and then applying a closed cell poly “Prodex” brand white faced on the bottom leaving the 3 1/2 inch air gap between the two. Prodex is claimed to be r16 and the rigid r10. Or is there a more suitable way to do the ceiling like cutting board to fit between said trusses and using Prodex on bottom with no air gap?  

 Thank you for your help.  I’m finding hundreds of articles and advice on metal buildings which mine is not and trouble finding a solution for my project.  Oh, and I live in northern Ohio”

Good move having Tyvek in your walls to prevent weather from seeping into your insulation cavity. If your walls are tightly framed (which they should be) the possibility of rodents getting into your wall cavities should be zero. Cutting and fitting insulation board to fit between framing members sounds like a mountain of labor, as well as pretty near impossible to be able to get a tight fit against every stud. I’d be inclined to use either closed cell spray foam insulation or BIBs insulation for walls.

Prodex is a radiant barrier and your chances of getting a measurable R value out of it more than one and change is not good. In a thorough 2010 study by the Canadian National Institute for Research in Construction, their conclusion: In a perfect state (with no dust on the surface), a radiant barrier with an air gap increased the efficiency of insulation in a wall by 10%. In other words, if the wall was already R6, adding ‘miraculous’ foil bubble wrap added .6, for a total of R6.6.

The best way to insulate your ceiling is to blow in cellulose or fiberglass to at least R45, if not R60. Do not place a vapor barrier under blown in insulation. Make sure the attic space above the insulation is adequately vented.

 

Mike the Pole Barn Guru