Tag Archives: French drain

Post Frame Construction On Clay Soils

Many years ago, when I first went to work at Lucas Plywood and Lumber in Salem, Oregon I was given a quick tour of some areas where new construction was prevalent. Having moved from sandy/gravel soils of Eastern Washington, I was totally unprepared for bright red clay soils in this Willamette Valley region. When wet walking across these soils would add huge and heavy red clay mud balls to work boots.

Post frame (pole) building construction, or indeed any type of building, can become problematic when dealing with clay soil.

Reader JEFF in GAMBIER writes:

“I have a high water table, a 24 in diameter 5 foot deep augured post hole in clay soil will fill up in 3-4 days with water. Will a CCA treated 0.60 retention 3 ply glu-laminated post survive in these conditions or is this a good place for the concrete “perma-columns”.”

Mike the Pole Barn Guru says: Let’s take a step back – to site preparation:

At a minimum, site preparation includes:
· Remove all sod and vegetation.
· For ideal site preparation, remove topsoil and stockpile for later use in finish grading. In frost prone areas, remove any clays or silty soil
from within future building “footprint”.
· Replace subsoil removed from around building with granulated fill to help drain subsurface water from building.
· Distribute all fill, large debris free (no pit run), uniformly around site in layers no deeper than six inches.
· Compact each layer to a minimum 90% of a Modified Proctor Density before next layer is added. Usually, adequate compaction takes more than driving over the fill with a dump truck, or
earth moving equipment.

Why would clay be an issue to build upon? Clay expands and contracts depending upon amount of moisture present. When wet – clay expands, when dry it shrinks. These movements will cause buildings to move as well – not a good thing.

You might also add a french drain beyond the building perimeter, in order to direct water away from your site. Make sure to slope the ground away from your new building, no less than a 5% slope. Downspouts should discharge water at least five feet away from building.

Whether your site is adequately prepared or not, properly pressure preservative treated columns should provide more than a lifetime of use. Your real question to be answered is if you want your building to be stable and straight, or if you are willing to accept it moving up and down, in and out (and perhaps randomly) with time.

Dear Guru: Should I Add Closures?

New!  The Pole Barn Guru’s mailbox is overflowing with questions.  Due to high demand, he is answering questions on Saturdays as well as Mondays.

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 or Saturday segment.  If you want a quick answer, please be sure to answer with a “reply-able” email address.

Email all questions to: PoleBarnGuru@HansenPoleBuildings.com

 DEAR POLE BARN GURU:I have a pole building reroofed with 1′ overhangs and am wondering if you think I should/need to use closures or something at the eave to seal the ribs. Thanks FREAKING IN FOSTORIA

DEAR FREAKING: I’d recommend the use of form fitted inside closures on top of the eave girt, if you have enclosed overhangs, or on top of the eave girt with open soffits. There should also be form fitted outside closures on top of the roof steel underneath the ridge cap. This combination will help to keep those nasty little flying critters from joining you inside of your building.

DEAR POLE BARN GURU:water drainage. BUDDY IN HOLLEY 

DEAR BUDDY: Not entirely sure how to best assist you from the two word question. Assuming your new pole building is not going to be used as a home (in which case I would make entirely different recommendations using a raised wood floor), I’d approach this as for any pole building drainage solution. I would order columns long enough to get the required depth to extend below the frost line, plus make up for any grade change. After the columns were set, I’d bring in good compactable fill to get the elevation of the bottom of any future concrete slab above the highest point of the surrounding grade. Above the high side of the building, a French drain can be installed to divert any natural drainage. For those who are unfamiliar with French drains, it is when a trench is dug beyond the building perimeter, drain rock is placed in the bottom, then one or more rows of perforated four inch pipe are laid. After placing the pipe, the balance of the trench is filled with drain rock. I hope this helps – if not…please email me more information.

Dear Pole Barn Guru: What is the Best Pole Building Drainage?

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.  If you want a quick answer, please be sure to answer with a “reply-able” email address.

Email all questions to: PoleBarnGuru@HansenPoleBuildings.com

DEAR POLE BARN GURU: Looking at a 40×60 pole barn on my 80 acre property. Weighing all the usual options, but the biggest issue that I have is the site. There is a couple degree down-hill pitch towards the site that the building will be built. Traditionally, we would put in a frost wall foundation, high enough so that the swale could divert any runoff around the building. Given I’m much more inclined to go with a pole barn at this site, what can I do to get the building up off the ground high enough to avert any natural pole building drainage from running under the barn?

I am used to traditional foundation/stick framing, but not sure about sub-foundation planning for pole barns.

Thanks for helping! LIGHTENING IN GOOD THUNDER

DEAR LIGHTENING: Assuming this is not going to be used as a home (in which case I would make entirely different recommendations using a raised wood floor), I’d approach this as for any pole building drainage solution. I would order columns long enough to get the required depth to extend below the frost line, plus make up for any grade change. After the columns were set, I’d bring in fill to get the elevation of the bottom of any future concrete slab above the highest point of the surrounding grade. Above the high side of the building, a French drain can be installed to divert any natural drainage.

For those who are not familiar with the term – a French drain is when you dig a trench and then put some drain rock in the bottom of it. Then lay in one or more rows of perforated 4 inch pipe and fill the rest of the trench with drain rock.

DEAR POLE BARN GURU: Looking around on your website, I seem to be unable to find the dimensions and wood species, and shape of the poles that come with your buildings.  Help? FREAKYALIENBABY

DEAR ALIEN: There are many variables which are going to influence the answers to your question. One of those is going to be geography – where the building will be constructed.

The other is, what loads will need to be supported by the columns. As wind and/or snow loads increase, so will the size of the columns.  Whether it’s enclosed or “roof only” makes a huge difference, as well as eave heights over 16’.  I mention only a few of the variables here as examples.

As to dimensions, we use 4×6, 5×6 (In some parts of the country 4×6 and 6×6 are not available, but 5×6 is), 6×6, 6×8, 6×10.

In the East and Midwest, the species with be SYP (Southern Yellow Pine); in the west HFir (Hem-Fir).

We also use glu-laminated columns, anything from 3 ply 2×6 to 4 ply 2×8 and larger.

The shape?  Not round – these are not fence posts nor telephone poles.  They will be square (if 6×6) or rectangle if dimensions are not equal on both sides.

If you decide you want certain size columns – because it makes you “feel like it’s sturdier”, that’s fine, as long as they meet code.  For example – we’ve had folks request “all 6×6’s” even though they don’t understand under certain conditions a 4×6 will outperform a 6×6, and going to a 6×6 gave them no added “strength” to their building.  They basically paid for larger columns – for no added value.  But that’s a topic for another blog.  Once you get a quote and are ready to purchase, we can give you a pretty good idea of what size columns will be used on the building you plan to purchase – according to the loads applied to it – and the size.  Hope this helps!

 DEAR POLE BARN GURU:  Who do I go to to get the information regarding my proposed building’s Code requirements for wind and snow? Would code enforcement have it?  MEANDERING IN MAINE

 DEAR MEANDERING: Typically most jurisdictions have a department such as : “Building”, “Community Development”, etc. – they are the department you would need to go to in order to acquire a permit to build.

If unable to easily determine: if you are in the city limits, call city hall. If outside of city limits, call the county courthouse. Ask either who you would need to speak with to obtain a building permit.

DEAR POLE BARN GURU:  I am pricing post frame building.  One mfg uses 26 ga steel while another uses 29 ga.  Which is better when not considering price?  Is tensile strength a big consideration? HIKING IN FROM HERON LAKE

DEAR HIKING: I suppose the real question to be asked is, do you NEED 26 gauge steel?

This article answers lots of questions about steel thickness:

https://www.hansenpolebuildings.com/blog/2012/01/steel-thickness/

Tensile strength is a consideration, as it will directly affect the strength and spanning capabilities of the steel. To the best of my knowledge, all of the major steel roll forming companies are manufacturing 29 gauge product with an 80,000 psi minimum tensile strength. There is a company which is providing 26 gauge product which is softer, it has a lower yield point. This allows for the steel coil to be roll formed into siding on machine with fewer dies stages, which reduces the investment needed into the machine. Although their steel panels are thicker, they won’t span any further, as the steel is not as strong.

DEAR POLE BARN GURU: I have read dozens of different opinions, many contradicting each other, on condensation.  I have built a monitor style pole barn 44×40 with a 20′ raised center isle.  Will have a 20×20 loft that will be finished and insulated.  The rest will be open shop space.  I have the trusses on 48″ centers with 2×4 purlins laid flat on 24″ centers.  I need to know what will be the best underlayment to put between the metal and purlins.  I was looking at solid attic foil, that is basically, a vapor brainier and radiant barrier, with no insulation.  But I saw an article that said that it would still condensate on the bottom of the attic foil.  I will be using 26ga galvalume screw down panels, and I am in north Louisiana. LOOKING IN LOUISIANA

DEAR LOOKING: Easiest solution is to place reflective insulation, like an A1V product between the roof purlins and the roof steel (see www.buyreflectiveinsulation.com).

Other important things to do – make sure to place a good vapor barrier under your concrete slab. https://www.hansenpolebuildings.com/blog/2012/09/concrete-slab-3/

You also need to have proper ventilation – with good intakes at the eaves from vented soffits, as well as a vented ridge. https://www.hansenpolebuildings.com/blog/2014/02/pole-building-ventilation/

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: PoleBarnGuru@HansenPoleBuildings.com

DEAR POLE BARN GURU:

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.