Tag Archives: drip stop

Condensation Prevention, Sound Proofing, and Snow Loads

This Wednesday the Pole Barn Guru tackles reader questions about condensation prevention by placing foam board over the top of 2×4 purlins, options for sound proofing a post frame home, and if 2×4 flat purlins can hold a specific snow load.

DEAR POLE BARN GURU: I am planning a pole barn; the roof will have 2×4 purlins spaced 24″. I plan on putting 1/2″ foam board (faced on both sides) over the purlins with the seams taped. Then putting metal panels over the foam board. Will this be sufficient to prevent condensation from dripping within from the roof? JIM in MIDLAND

DEAR JIM: Good news and bad news…. while your proposed solution will likely take care of possible condensation issues, it is structurally unsound. Post frame (pole barn) buildings rely upon shear strength of steel roofing and siding in order to remain stable. When you add in even a half-inch gap of non-rigid material (foam board) between framing and steel skin, you greatly reduce (or eliminate) shear strength of your steel panels. Even if your building were to remain standing, shifting of steel panels with small diameter (#9 or #10) screws will cause slots to form around screw shanks, eventually causing leakage.

You would be best served to order roof steel with an Integral Condensation Control (read more on I.C.C. here https://www.hansenpolebuildings.com/2020/09/integral-condensation-control-2/) factory applied. It will be less costly, easier to install and not cause negative structural issues.

 

DEAR POLE BARN GURU: Afternoon! Thanks for all the great info in your blog. It has really helped me plan my new home. I have one question: I’m having a post frame home built and am wondering about soundproofing. The roof(s) will be steel directly on purlins with a radiant barrier in between. The conditioned space will have R-60 blown-in fiberglass above it so I’m not worried about that. What I am concerned with are the front and rear porches. The front will have a, 8″ shed roof porch and the rear will have a 16×16 gable-roof screened porch. Both will have finished ceilings, steel and knotty pine respectively. I’d like to be able to sit under either when it’s raining and it not be loud. What would you suggest I do to mitigate the drum effect in an uninsulated porch? I’ve thought about using rockwool batts, maybe mass-loaded vinyl, or even painting the underside of the steel with liquid rubber before the panels are screwed down. Any advice? Thanks much. PETER in HUDSON

I am pleased my information has proven helpful to you. I would consider one of two options – installing steel in these two areas over solid sheathing (OSB or plywood) with 30# felt or a synthetic underlayment, or using two inches of closed cell spray foam applied directly to underside of roof steel. Either of these should assist in mitigating sound.

 

DEAR POLE BARN GURU: In an area with a 50 p.s.i. snow load ground rating and trusses 4′ o.c., can 2×4’s 2ft. o.c. be laid flat for roof purlins? STEVE in WYOMING

DEAR STEVE: Maybe – this will depend upon numerous factors including (but not limited to):

Risk Category of building
Roof slope
Wind Exposure
Roofing material
Snow retention systems
If building is heated or not
Available grade of lumber

Ultimately this decision should be made by whomever your engineer is who is sealing your building plans. Special care should also be taken to insure adequacy of purlins in drift zones (closest to ridge), where purlins may need to be closer spaced, higher grade and/or larger dimension material.

Also – ground snow loads (Pg) are typically expressed in p.s.f. (pounds per square foot), rather than p.s.i. A p.s.i. of 50 would equate to 7200 p.s.f

Condensation Control, Mother/Daughter Addition, and Vapor Barrier for Roof

Today the Pole Barn Guru answers readers questions about condensation control in a small garage with a gravel floor, the possibility of adding a “mother-daughter” unit to her house, and “ribbed vapor barrier” for a shed roof.

DEAR POLE BARN GURU: Recently purchased a metal garage kit, 24X26. No insulation. Two garaged doors. Gravel floor with plastic under grave. I am getting condensation on some days, that makes my cars, etc have like a dew on them.

My rib looks to be 1” and 7” between ribs. How do you install a wall vent with the ribs? JODY in ALTON

Machine ShopDEAR JODY: First step is to take care of your source. Pour a concrete slab on grade with a well sealed 10-15mil vapor barrier underneath. As you have no thermal break between your warm moist air inside building and roof steel, have two inches of closed cell spray foam insulation applied to underside of roofing. You would be better served to vent eaves and ridge, than just gable vents. If gable vents are your choice, look for vinyl vents with a snap ring as they can be installed on ribbed steel siding.

Using inward vent base edges as a guide, mark area to be cut on endwall steel INSIDE, make hole cut square with steel sheet (vertical cut lines parallel to steel ribs). Cut hole with appropriate tools.
Push vent base through hole in steel from inside.
Note word “TOP” on base when positioning. Vents installed with top side in any direction other than up will allow water to leak into building.
While holding vent base in place, snap face into base from steel exterior by pressing firmly (this takes two people).

 

DEAR POLE BARN GURU: I’m interested in building an attached mother/daughter addition to my home. Do you have plans for that? Approximately 600-700sq ft. NANCY in MONROE TOWNSHIP

Floor PlanDEAR NANCY: Thank you for your interest in a new Hansen Pole Building. Every building we provide is custom designed to best meet the wants, needs and budget of our clients. We offer a floor plan design service for folks just like you: http://www.hansenpolebuildings.com/post-frame-floor-plans/?fbclid=IwAR2ta5IFSxrltv5eAyBVmg-JUsoPfy9hbWtP86svOTPfG1q5pGmfhA7yd5Q 

 

DEAR POLE BARN GURU: We are having a 50×30 all metal building. We were advised to get ribbed vapor barrier for roof. We have searched everywhere. Is it called something else? SHANNON in OLEAN

DEAR SHANNON: We are also not familiar with any product known as a “ribbed vapor barrier”. We would normally recommend use of roof steel with an ICC factory attached (https://www.hansenpolebuildings.com/2020/09/integral-condensation-control-2/). If this is not an option (or if you are using closed cell spray foam directly to underside of roof steel), next choice would be a radiant reflective barrier – look for six foot wide rolls with an adhesive pull strip attached for ease of installation.

 

Ceiling Insulation, Drafting Capabilities, and 24″ On Center Framing

This week the Pole Barn Guru answers reader questions about “ceiling insulation” for a roof rebuild, the capabilities of our drafting and proprietary pricing program, and “what percentage of pole buildings are 24″ on center?”

DEAR POLE BARN GURU: The birds have destroyed the front half of the ceiling insulation in our 40 x 60 pole building. We need a new roof and we plan to take out all the insulation when the roof is done. We don’t know what else to do because if we leave the insulation in the back half of the ceiling, the birds may destroy that also. What do you think? SHARON in STERLING

DEAR SHARON: Typically when I hear people talk about birds having destroyed pole building insulation I think of what is commonly known as Metal Building Insulation. Usually this is a thin layer of fiberglass with a white vinyl face – and once birds get started into it, there is no turning back https://www.hansenpolebuildings.com/2018/09/spot-problems-with-this-pole-barn-photo/

If you are doing a reroof, to control condensation your should look at ordering roof steel with a factory applied I.C.C. https://www.hansenpolebuildings.com/2020/09/integral-condensation-control-2/

 

DEAR POLE BARN GURU: I was curious on what program you use to make your plans? Does it do take off and quotes with the drawings? Can you design the interior also the exterior to make a shouse? TIM in NORFOLK

instant pricingDEAR TIM: Always a pleasure to hear from a “lumber guy”. Our blueprints are actually drafted individually on AutoCAD, however we are gradually transitioning to where most fairly straightforward work will be automated from our trademarked and proprietary “Instant Pricing” system. We searched everywhere trying to find a computer program able to actually accurately do a structural analysis of post frame buildings and found none existed. We created our own and added to it abilities to do real time quotes for any climactic condition and anywhere in America. Our program does quotes, invoices, material takeoffs, creates purchase orders and interfaces with our client data base.

While it can do interior walls, we opted to create a full service program for shouse and barndominium plans with a real person interacting via screen sharing so clients can watch their homes appear before their very eyes from the comfort of their homes.

 

DEAR POLE BARN GURU: What percent of pole barns are on 24″ centers? BRUCE in SXARTZ CREEK

DEAR BRUCE: There are numerous components of post frame (pole barn) buildings often placed 24 inches on center. Among these could be wall girts, roof purlins, sometimes roof trusses (most often seen with shingled roofs), floor joists or floor trusses over crawl spaces, basements and for second or third floors. One of fully engineered post frame building design’s beauties is there is no obligation to be at a specific spacing and materials can be utilized for their full structural capacities – making them extremely cost efficient.

 

 

Concrete Considerations from the PBG!

DEAR POLE BARN GURU: Is concrete included in price? TRACEY in SUMTER

DEAR TRACEY: No, we do not include concrete in the price and here is why:

Most familiar, as well as most available is the Sakrete® general purpose High Strength Concrete Mix. When mixed per the manufacturer’s instructions, this mix affords a compressive strength of 4,000 psi (pounds per square inch) at 28 days.

The instructions are: Empty the contents into a mortar box, wheelbarrow, or mechanical mixer. When mixing by hand, form a crater for adding water.  Add water a little at a time.  Avoid a soupy mix.  Excess water reduces strength and durability and can cause cracking. A 60 lb. bag should be mixed with three quarts of water, an 80 lb. bag four quarts.

Now the realities of using bagged concrete for post frame building footings….

treated postIt is not unusual to have concrete encasements of 24 inches or larger in diameter and 18 inches or more in depth, in order to prevent building settling and uplift issues. One hole this size would take 4.71 cubic feet, or about 700 lbs. of concrete! Even a very small building with 18 inches of diameter and depth takes 2.65 cubic feet or about 400 lbs. of concrete.

With either 60 or 80 lb. bags, it is going to take a lot of bags! An average building could easily have 20 posts, and if looking at 700 lbs. of concrete per post, we are talking about 7 TONS of concrete (3-1/2 yards).

Ignoring the huge number of bags involved, there are some other realities.

Ever looked at the pallets of readi-mix bags at the lumberyard? Take a peek, next time. Notice how many of them are broken or leaking.

Due to weight, it may very well mean another delivery and another delivery charge. Trucks do not run for free.

Bags can (and will) break when being handled during delivery, unloading and being moved around the jobsite. It is going to happen, just plan on it.

From experience, lots of projects are not begun immediately after delivery. It is not unusual for delays of weeks, or even months before actual construction begins. Improperly stored, bags can get wet or absorb moisture and become solid before time for use. This equals a total waste of money, other than the chunks of concrete make for solid backfill.

Then there are the builders who insist upon throwing the entire bag (usually including the bag) into the hole. Their idea is ground water will cause the readi-mix to harden. Why does this not resemble the manufacturer’s instructions?

Readi-mix must be mixed thoroughly and evenly. How does mixing over 200- 60 lb. bags of Sackrete® by hand sound? Add too much water (three quarts exactly per 60 lb. sack) and the strength is reduced.

Use too much? As holes are always perfectly round (not), it is going to happen.

Save time, effort and money. Often all three can be saved by having the local pre-mix concrete company deliver concrete for holes (even if a “short load” fee is charged), as opposed to mixing on site.

DEAR POLE BARN GURU: I am building a 36 x 40 pole barn and I’m on a grade that drops approximately 4′ over the span of the building footprint. A home builder friend, a structural engineer, and my concrete guy have recommended traditional foundation with wet set permacolumns, but the builder I’ve contracted with wants to set columns on footers 3′ to 5′ in the ground and not use the permacolumns. The pole barn builder doesn’t think I need a retaining wall and should just have an excavator level what i need with a slope off the back. Seems a retaining wall in the back is better, which my concrete guy will pour, but still recommends foundation to eliminate frost heave. Use for building is car storage and shop with a lift.
Thank you in advance for your time and help. CHRIS in ST. LOUIS

DEAR CHRIS: This reminds me of a joke I once heard – a home builder friend, a structural engineer and a concrete guy enter a bar…….

Oops, kind of off track!

Some of the answer is going to depend upon what you want your yard to look like.

In any case – the actual pad of the building is going to need to be properly compacted (emphasis on proper) so those costs will be fairly even in any case. You’ll want to be reading about proper site preparation and compaction here (it is lengthy): https://www.hansenpolebuildings.com/2011/11/site-preparation/

What might appear to be the least expensive would be to just order columns long enough to get the required embedment depth as shown on the engineered plans, then fill afterwards, sloping away from the building. In order to keep the fill from sloughing off, it will probably result in a slope next to your building which will stretch out as far as 20 feet. You could easily invest in several hundred yards of fill!! If you can live with the look, might be the answer.

Building on top of a foundation – this is going to be the most expensive and certainly not the choice I would probably be making. It is also going to be tougher to build upon, due to the height of the walls plus the foundation.

Which leaves – build a retaining wall. I like this idea. Columns do not have to be longer (as long as fill is properly compacted).

By the way – there is no reason for ANY of these versions to frost heave as long as the site has been properly prepared. Read more about how to avoid frost heave issues here: https://www.hansenpolebuildings.com/2011/10/preventing_frost_heaves_in_pole_building_construction/

DEAR POLE BARN GURU: How much is the drip stop application for labor/material? Usually it comes already attached to the metal paneling. Do you figure it by square feet? JOSH in MANKATO

DEAR JOSH: For materials you are going to be looking somewhere in the neighborhood of 53 cents per square foot of roof surface. As a builder, if you are anywhere it is typically windy, I am going to give you a decent discount on my labor for having invested in it, because I don’t have to fight rolls of insulation flapping in the breeze.