This week the Pole Barn Guru answers reader questions about cleaning up rough cut lumber that has greyed from exposure to the elements, advice on house wrap and insulation, and the ability of flat purlins over trusses to carry a load in Kentucky.

DEAR POLE BARN GURU: My barn project has been a long drawn out process. The project stalled for 6 months but has picked back up again. I’m using rough cut lumber. Unfortunately, the wood has a grey color to it (probably from dirt, mold or algae on the surface).

What’s the best way to clean it to make it look fresh/revived again? Any products that you recommend?

Thank you again for all your help and advice. JAMES in MILTON

DEAR JAMES: Clean with sodium percarbonate or hydrogen peroxide, then apply oxalic or citralic adid (second step restores wood to its natural pH and neutralizes sodium percarbonate cleaner).

DEAR POLE BARN GURU: I added a lean-to to my 60×90 pole barn. The builder put house wrap around exterior walls. When the tin guys put up the metal they put bubble wrap over the house wrap then the metal. I spray foamed with closed cell inside 2 inches. The interior will be knotty pine so do I need to put another barrier before the wood? Also on the roof they put the bubble wrap under the steel I will have blow in on top of the knotty pine. I plan on putting plastic sheathing before the knotty pine. Is this the correct way of doing or should we change something? SCOTT in KOUTS

DEAR SCOTT: It was bad enough when your tin guys put bubble wrap over your housewrap. Compounding your having spent your hard earned money on both, is closed cell spray foam should have been applied directly to inside of steel siding. Water under a bridge at this point. You should fill balance of wall cavity with unfaced rock wool and no interior vapor barrier. Wall will now dry to inside (meaning you may have to mechanically dehumidify). You did not say if your added lean to has an attic space or not. If your intent is to insulate with plane of roof (purlins) here is some guidance: https://www.hansenpolebuildings.com/2023/10/properly-insulating-between-roof-purlins/

If you are insulating above a lower ceiling height (as you say blow in – I will guess this is your case), in your Climate Zone 5A a vapor retarder should be on warm in winter side of insulation (not a vapor barrier, like plastic sheeting). A vapor retarder could be as simple as kraft facing from batt insulation, or latex ceiling paint. Make sure to adequately vent any non-conditioned attic space.

DEAR POLE BARN GURU: I love reading your posts. I’ve learned much about your ideas and it’s changing the way I think. Thank you. Iowa and SD have different wind and snow loads than central KY. I routinely see farmers building barns with 2×4 purlins laid flat on trusses spaced every 8 feet. Your designs call for 12 spacing, which I love, and 2×6 purlins on edge in joist hangers. Would 2×4 purlins in joist hangers work in central KY?

CHRISTOPHER in RICHMOND

DEAR CHRISTOPHER: Thank you for your kind words.

We have provided fully engineered post frame buildings in places with no snow, to places where snow load is over 400 pounds per square foot – so we have pretty much seen it all!

Those farmers laying 2×4 purlins flat (wide face to sky) spanning eight feet are risking not only their buildings, but their lives. I am amazed they can even apply roof steel to them without failures.

For 12′ spans, without snow, purlins on edge, 2×4 2400 msr roof purlins 24 inches on center would carry loads, however would overly deflect. You could probably use 2×4 #2 Southern Pine at 12 inches on center, however 2×6 #2 at twice spacing would be more economical both in materials and labor.

Read more about msr lumber here: https://www.hansenpolebuildings.com/2012/12/machine-graded-lumber/