Dear Pole Barn Guru: Will a Drain System Hurt My Piers?

Welcome to: Ask the Pole Barn Guru – where you can ask questions about building topics, with answers posted on Mondays.  With many questions to answer, please be patient to watch for yours to come up on a future Monday segment. 

Email all questions to:


I have a 40′ L X 30′ W metal pole barn, which has a 10′ overhang.  Basically the foot print is 40 X 40.  The roof has a 6/12 pitch that is connected to the overhang roof, which transitions to about a 3/12 pitch.  I live near Buffalo, New York and have a problem with gutters on the overhang.  Every year the snow wants to pull down the gutters.  I don’t really like the idea of putting up snow jacks because it’s just more holes that I’m putting in the roof and I feel like I would be compromising the integrity of the roof over time.  I have read about the use of French drains and though I would just eliminate the gutter on that side and install a French drain.  I’m wondering if I “opened up a can of worms” and would be causing more problems than it’s worth.

I dug a trench about 18″ wide and 24″ deep along the side of the pole barn.  My plan is to place #2 clean washed stone with perforated SDR35 pipe in the trench leading out to ground level on the slope behind the barn.  The drain pipe will be wrapped with a filter sock and the stone surrounding the pipe will be wrapped with designed trench filter paper.  This should prevent silt from entering both the stone and also the pipe.

My concern is not so much with the design of the French drain, it is more with the pole barn piers.  Will I be compromising my piers with this drain system?  When I dug the trench I went down about 2′ next to the footings all along the one side.  Am I now creating a frost or heaving problem with those pier footings?  I would appreciate your help before I create a problem here.  Thanks. Darien Dan

DEAR DAN: Without having a geotechnical engineer personally visit and inspect your building site, I can only give generalized answers, so here goes….

Will you compromise your piers with this drain system – it is possible. The extra water being added into the ground system could cause not only frost heave issues, but could also contribute to settling of the columns. Besides potential frost heave and settling issues – the drain system is not probably overly economical in either time or cash outlay.

Provided your roof system was properly designed for the added weight, there are several polycarbonate snow retention systems for roofs which will not cause you to have to put any more holes in your roof. A special adhesive is used to glue the snow guards to the steel roof surface. Once installed, snow should adequately stay on your roof, keeping the gutters where they belong, instead of on the ground next to your building.


DEAR POLE BARN GURU:  Can fink truss 6″ pitch  and 24 ft span  be on 2 ft centers. Inquiring in Arkansas.

DEAR INQUIRING: In background – a “fink” style truss is one in which the interior truss members (or webs) are in the shape of a “W”. In some cases, it is referenced by the number of “panels” (spaces between the truss webs) from one side of the truss to the other. In the case of a fink truss, the top chord would have four divisions, the bottom chord three.

A 6” pitch is one where the sloped top chord of the truss, gains six inches vertically, for every 12 inches of horizontal movement.

As to whether your span, slope and spacing combination will work or not, would depend upon the design loads which the truss is expected to carry. These loads include sloped roof snow load, dead loads from roofing, sheathing, insulation, ceiling materials, etc., as well as wind loads.

To be safest, take your complete building plans to the prefabricated wood roof truss manufacturer of your choice and they should be able to use this information to design and quote the project.

Leave a Reply

Your email address will not be published. Required fields are marked *