Tag Archives: sealing concrete floor

How to Insulate a Post Frame Shop

How to Insulate a Post Frame Shop When No Advance Considerations Were Made

I encourage clients to give some serious advance consideration when erecting new post frame (pole) buildings to any eventuality of future climate control and a need for insulation.

Reader MAC in MILLVILLE writes:

“40 x 30 want to insulate. It will be used as a storage/workshop. I included pictures so you can see what I have. What’s the best way to insulate? I plan on doing metal ceiling liner and most likely plywood on the walls. There is no vapor barrier under the concrete either. I do have a vented ridge and soffit. I hope I provided enough information to be able to answer my question.”

Start by sealing your concrete floor – as this is going to be a moisture source you do not want inside of your new building.

Roof/ceiling – no provision has been made to prevent condensation from happening beneath your roof steel. Sadly I see this occur far too often, as builders, kit providers and local lumberyards just lack knowledge needed to be able to educate and make best recommendations to their clients. You could either (a) remove roof steel, add a method of condensation control (such as a Reflective Radiant Barrier or sheathing such as OSB or plywood with either 30# felt or a synthetic ice and water shield) and reinstall steel using new, large diameter screws. This is highly labor intensive and your roof may not have been designed to support the weight of adding sheathing.

Best solution will be to have two inches of closed cell spray foam applied to the underside of roof steel at roughly two dollars a square foot. Not an inexpensive solution when its need could have been prevented with better advice up front.

Cumberland County is in Climate Zone 4A, as such you should have a minimum of R-49 ceilings and R-20 walls. Perimeter of your slab should be insulated two feet deep with R-10.

I would dig a trench two feet deep around your building, up tight to its pressure preservative treated splash plank and install R-10 rigid board XPS insulation from the height of the top of the slab down two feet. Install a metal, cement board, or cellular PVC panel to conceal any insulation portion left exposed above grade. If cement board is used, it should be a type not reinforced with wood fibers. Install a metal cap as an insect guard to conceal the top horizontal edge of both insulation board and closure panel. Seal cap to splash plank with mastic.

Once you have a ceiling liner in place, blow in R-49 or greater thickness of fiberglass insulation.

For walls, I normally like to see a Weather Resistant Barrier (like Tyvek) between framing and siding. As you do not have this, I would use R-21 unfaced Rockwool stone wool insulation, as it is not affected by moisture. Place a well-sealed 6mil clear plastic vapor barrier over the inside of insulation prior to placing plywood on walls.

Concrete Sealer to Moisture Proof an Existing Concrete Slab

We were at a vendor event for the DirectBuy in Beaverton, Oregon when a member approached us looking for advice on how to seal an existing concrete floor in her pole barn. It seems the floor is always damp.

I’ve always recommended placing an insulated vapor barrier beneath any new interior concrete floor. I’ve had great results personally with the A2V product available from www.buyreflectiveinsulation.com. For those who are too late, there is a solution.

Concrete floors are notoriously damp, as moisture will pass through concrete. Think of concrete not as a solid, but instead as being a sponge – albeit a very heavy sponge.

When a concrete slab floor is not sealed, the moisture in it becomes added humidity to the inside of your building.  Over time, this will encourage the growth of mold, mildew, rot, and dust mites in your pole building, leading to damage to your building materials along with adding unhealthy allergens to your interior air space.

By sealing the concrete with a penetrating concrete sealer, moisture-related issues with concrete floors can be quickly and easily avoided.

Concrete is a porous material which will accept water, moisture, and water vapor readily from the foundation soils beneath pole barns. This moisture can be passing through in the form of water vapor even when the slab floor doesn’t appear to be damp.

One way to test the amount of moisture passing through a slab floor is to lay a sheet of plastic on the floor for several days. If the surface under the plastic is damp, then there is evidence of moisture penetration through the concrete slab.

Along with moisture, water will bring a small amount of minerals with it. As the water passes into the air, this will be left behind as a mineral salt known as efflorescence, which appears on floors as a white, powdery substance.

A solution is a silane-based concrete sealer. These sealers penetrate deep into the pores of the concrete, activating with the minerals in the concrete to create a glass-like barrier deep within the concrete. They’re safe to use indoors, and contain little or no VOC’s (volatile organic compounds – brand depending).

A silane-based concrete sealer activates quickly, and can be applied to both cured and newly-placed concrete. It will not change the appearance of the concrete, efflorescence and acidity will not harm it, and the concrete floor is able to be painted over with ease. Installation is fast (done with a brush, roller, or sprayer), and they’re middle-of-the-road in overall cost.

There are several disadvantages to consider.  One, a concrete sealer provides moisture control only, thus will not be able to breach cracks or stop flooding water. Second, it’s meant only as a sealer for water vapor which would otherwise pass through the pores of the concrete. Third, care must be used when installing as silane-based sealers cause etching on glass, should they come in contact with it. When installing, be sure to protect and/or avoid glass surfaces. And lastly, when installing be careful to only use enough silane-based concrete sealer to damp the concrete, as too much will leave a white residue behind.

Silane-based sealers are the ideal choice for concrete slab floors which are damp but do not flood, as they are inexpensive, install quickly and subtly, and provide a lasting solution.