Tag Archives: moisture barrier

Addition to House, Stone Floor Moisture Barrier

Today the Pole Barn Guru discusses a post frame addition to a house, whether or not one should use a plastic barrier under the stone floor in a steel building, and the ability of a truss carrier to handle imposed loads.

About Hansen BuildingsDEAR POLE BARN GURU: Hi! We are considering a sizeable addition to our 600 sq ft bungalow style home, somewhere in the neighborhood of 30×40 ft addition. Wondering if it’s possible to do pole barn construction for this addition, and what kind of considerations would need to be made? The current home does have an existing basement with block foundation. I’ve read information regarding attaching a pole barn build to an existing house for use as a garage, but wondering how this scenario changes things? We would work with a licensed designer to draw up plans, and a licensed contractor for the build, but are just in the brainstorming phase at this point. KARI in WILLMAR

DEAR KARI: There are actually no real considerations for post frame not applicable to a stick frame building. You should work with a Hansen Pole Buildings designer for your building shell and we can provide engineer sealed plans for structural portions of the addition. You can work with an independent designer (FYI – there isn’t a category of licensing for designer) or create an interior layout of your own.

DEAR POLE BARN GURU: Should I put plastic down under the stone floor in a steel building? BOB in WYALUSING

DEAR BOB: It certainly would not harm anything and will help to minimize condensation issues. Look at a 15ml thickness. For more information on vapor barriers see: https://www.hansenpolebuildings.com/2017/11/vapor-barriers-slabs-grades/

 

DEAR POLE BARN GURU: Really wondering if a 2×12 SYP MSR 2400 will hold my 32ft trusses 2ft oc poles 6×6 8 oc. 1 2×12 on outside and 1 on inside. Is the 2×12 SYP MSR 2400 strong enough to hold the weight? CHRISTOPHER in CHESTERFIELD

CHRISTOPHER: In answer to your question – maybe. It will depend upon a myriad of factors including (but not limited to) Ps (roof snow load adjusted for slope), Dead loads from roofing, any roof sheathing, truss weight, any ceiling or insulation.

If you are so inclined, you can try this calculation yourself:

complex formulaLOAD (in psf – pounds per square foot) X (½ building width plus sidewall overhang in feet X 12”) X Distance spanned by beam squared (in feet)

Divide this by 8 X 2400 X 2 (for two members) X 31.6406 (Section Modulus of a 2×12) X 1.15 (Duration of Load for snow).

If your resulting answer is less than 1 then your beams will probably work.

Caveats – LOAD is Ps + all dead loads. For steel roofing over purlins 5 psf would be my recommendation. If a ceiling is to be installed a minimum of 5 psf should be added (10 psf being better).

Some important factors other than just strength include deflection (especially if trusses support a gypsum wallboard ceiling), minimum required bearing area and shear force at edge of bearing.

Frequently overlooked is connection of beams to columns. Notching in would be preferred to each face of columns.

Ultimately, RDP (Registered Design Professional – architect or engineer) who provided your sealed plans should be making a determination as to adequacy as well as providing appropriate connections.

 

Blowing Attic Insulation

Blowing Attic Insulation, Without Vapor Barrier, Below Roof Steel

A very common problem I see involves people not preparing their post frame (pole barn) buildings to adequately be insulated.

Reader NED in THURMOND writes:

“Thank you for your help. I’m in process of completing a pole barn project. It’s divided into three sections…living area, workshop, and garage. The size is 24 x 44. The outside perimeter wall is 2×6 frame with OSB and metal on the bottom and metal only in the top portion. The wall cavity is filled with unfaced insulation and poly on the inside. The roof is 8’ oc trusses with metal panels and no moisture barrier. 6 mil poly was applied to the ceiling joists. I wanted to insulate the ceiling, so I removed the poly and plan to install Sheetrock and blow in R-38 overhead. The building has a ridge vent and soffit vents in the eaves. Do I need a moisture barrier on the ceiling or will the blown in insulation suffice? What, if any problems do you anticipate? Thank you so much.”


Mike the Pole Barn Guru responds:

Here are some anticipated problems –

Without some method of condensation control beneath your building’s roof steel you are going to have moisture problems. Blown in fiberglass or cellulose insulation will lose their effective R value once they get wet. A practical solution will be to have closed cell foam insulation sprayed upon roof steel underside. Normal recommendation would be two inches thick however your local applicator(s) can give you their best input from experience. Make sure spray foam does not block either eave air intakes or ridge exhaust points. You can create a “dam” at eaves to keep blown in insulation from filling soffits, by use of ripping high R closed cell insulation boards. Again, make sure not to block incoming airflow (you need a minimum of least one inch of free area above insulation boards).

Planning a new post frame building? If so, I encourage you to take appropriate steps for your building to have future insulation installed. Yes, there will be some initial investment involved.However it will be so much less expensive to plan for it now than to wish you would have later.

 

Turf Sweating, A Post Frame Addition, and A Grow House

DEAR POLE BARN GURU: Hello, I am from Webster SD and I built a pole barn and insulated it.  I then put turf above gravel floor and use it for a indoor baseball practice facility.  It can be heated as we have heaters in there.  We have a huge problem and was wondering if you could help us solve it.  I went in there today and the humidity was 85%.  Under the turf is wet.  What is causing this and how do we solve it?  We have bats in there that are showing early signs of rust and it has been closed up for about a month.  Thanks, CHAD in WEBSTER

DEAR CHAD: The water is coming from the ground, and even makes its way up through concrete. You will need to remove the turf and then install a high quality sealed vapor barrier which is resistant to punctures or tears beneath it. In the research I have done, it appears the folks at Americover (www.americover.com) can probably make the best recommendations as to the product which will best fit your needs and budget.

Depending upon how you have insulated the building, it may also be necessary to add ventilation in order to remove excess humidity from the air.

DEAR POLE BARN GURU: Can a pole barn be mounted to a house that has a cinder block foundation? RAY in BROCKPORT

DEAR RAY: If the question is can a pole barn (post frame building) be mounted to a block foundation, as long as the foundation is adequate to carry the imposed loads, certainly. Brackets are made to either pour into a foundation, or be retrofitted to one.

If you want to attach a post frame building to a house with a cinder block foundation, the post frame building would not structurally rely upon the block. Instead, it would typically be a free standing structure abutted to the existing building and foundation.

 

 

DEAR POLE BARN GURU: Is a 28×24 pole barn with 8 foot ceiling height large enough to start a grow room? ELIZABETH in DUNDEE

DEAR ELIZABETH: It will depend upon how many plants you intend to grow. A mature plant requires four square feet of area and you need to have space to walk alongside. The eight foot high ceiling might be a bit tight as well, as some plants have the capability to grow to be as tall as a house. My best recommendation is to err on the side of caution and construct the largest footprint building which you can economically justify and which will fit within the available space.

 

 

Spray Foam Insulation with Dupont Tyvek House Wrap

Hansen Pole Buildings Designer Rachel asked me about this today:

“I have more and more builders say they put Tyvek® on the walls and roof and then spray foam.  This is so they can replace the siding/roofing in the future.  Do you find any downfalls with this?  I thought this was a pretty good idea.”

Having just written an article about spray foam insulation (https://www.hansenpolebuildings.com/2016/07/advantages-spray-foam-over-batt-insulation/), this is a well timed question.

Tyvek and all house wraps are NOT (I repeat NOT) vapor barriers. They are weather barriers: https://www.hansenpolebuildings.com/2016/01/determining-the-most-effective-building-weather-resistant-barrier-part-1/.

Spray-Foam-Insulation-150x150In doing my research on the whys and why-nots I found apparently there are some spray foam insulation contractors who will not spray foam against house wraps, apparently from not being able to guarantee their product would properly adhere to the house wrap.

In one particular case – the spray foam insulation contractor tried to persuade the client to use BIBS® insulation (read about BIBS® here: https://www.hansenpolebuildings.com/2011/11/bibs/) due to the potential adhesion issues.

There apparently is an adhesive additive for spray foam, which will assist in the foam being able to stick to house wraps or other slick surfaces.

As spray foam is a vapor barrier, and is resistant to moisture passing through it in either direction, adding a weather barrier to the outside becomes redundant.

If the idea is to use a product to allow for easy residing or reroofing, then a product such as clear visqueen (https://www.hansenpolebuildings.com/2013/07/moisture-barrier/) might prove to be as effective, as well as less costly than a weather barrier. This is, of course, providing the spray foam installer is willing to spray over it.

As a good, high quality steel roofing and siding should last the life of the building – installing any product between it and the siding, under the premise of making future replacement easier, it sounds much more like someone trying to make a feature into a benefit, than it does something which will add value to the client as a benefit!