Tag Archives: roof truss bottom chords

Spot Problems with This Pole Barn Photo

Spot Problems With This Pole Barn Photo

One of my Facebook friends had posted this as a timeline photo as it brought back to her fond memories of a childhood spent frolicking in hay lofts. It was so bad, I just had to save it.

So, what’s wrong with this photo anyhow?

Obviously bird excrement over everything does not pose a structural problem, but one which I would have been trying to minimize, if not avoid. One thing which was leading birds into building – excellent nesting material provided by what was once a vinyl faced fiberglass condensation control blanket (aka Metal Building Insulation).

Long ago I had espoused about joys (or lack thereof) involved in installation of Metal Building Insulation (https://www.hansenpolebuildings.com/2011/11/metal-building-insulation-in-pole-buildings-part-i/). For those of you readers who did not click upon link and read it in full, suffice it to say birds love fiberglass.

Once condensation control blanket was torn apart – there was nothing left to prevent condensation from occurring below roof steel.

Moving forward, just glancing upon structure supporting hay loft, I would suspect a high degree of under design with only chance keeping it from meeting its demise.

All sorts of things are seen hanging from trusses. Amongst these are a block and tackle, which I suspect has been used to lift bales of hay into loft. Fortunately, individual small hay bales are relatively light, as I am pretty sure trusses were not designed to support added point load weights.

While not most effective structurally, trusses can be designed to be placed upon each side of a column – provided they are done correctly. Blocking should be placed between truss bottom chords, in order to prevent weak axis bending. A bare minimum would be every ten feet.

I see no web bracing, making this highly suspect. Older barns tend to have had bracing needs neglected. Single trusses (when placed not nailed directly face-to-face into a pair, they are single) require a great deal of bracing.

Knee braces are what I see as biggest structural issue. Not only are knee braces ineffective (https://www.hansenpolebuildings.com/2012/01/post-frame-construction-knee-braces/), but when installed improperly (as in photo) they are potentially throwing a load into roof truss bottom chords trusses were not designed to withstand.

Feel free to chip in with your observations.