What if there is already a vapour barrier in the wall?

We tie into it, and we check whether there is a second one somewhere that would trap moisture between the two. Older McKernan renovations quite often have both, and finding that before boarding is worth the hour.

Is it a problem to have poly on both sides?

Yes. Two barriers trap moisture between them with no direction to dry. It is a real mistake we still find in renovated McKernan walls, and it stays invisible until the damage shows.

Does it matter where the sheets overlap?

Yes. A lap must land on solid framing and be sealed with acoustical sealant compressed between layers. An unsupported lap taped across a cavity flexes with pressure changes and works loose.

Why is there staining around my window reveals?

Usually the vapour barrier return at the window was torn or tucked rather than sealed. It is a cold junction, so condensation shows there first — often as staining or mould at the reveal.

Should I use poly or a smart membrane?

Most straightforward McKernan walls are fine with 6-mil poly, continuous and sealed. A variable-permeance membrane is worth it on retrofits and some basement details because it gives the assembly a drying path in both directions.

Vapour Barrier Installation McKernan Edmonton | 6 Mil Poly

Vapour barrier in McKernan, sealed as a continuous plane

Alberta winters put a large vapour drive from inside to outside, so the barrier belongs on the warm side of the insulation. Getting the position right matters as much as getting it sealed: a second barrier on the cold side traps moisture in the assembly with no way to dry.

Left ready for inspection before boarding
Seams lapped at framing and sealed, not just taped
Window and door returns detailed properly
Poly on the warm side of the insulation
Electrical boxes poly-hatted and sealed
Rim joists air-sealed before insulating

Laps, and the framing member behind them

Where sheets meet

A lap needs to land on solid framing and be sealed with acoustical sealant compressed between the layers, not taped in mid-air across a cavity.

Why it fails otherwise

An unsupported lap flexes with pressure changes and the seal works loose. In an McKernan build the sheets are planned so that laps fall on studs rather than wherever the roll ran out.

What a vapour barrier is not

It is not an air barrier by itself

Poly slows vapour diffusion. Sealed properly it also slows air, and unsealed it does very little of either. The sealing is what turns a sheet of plastic into a working assembly.

It is not a damp-proofing fix

If a McKernan basement has water coming through the wall, vapour control is not the answer and installing it will hide the evidence. That is a drainage and waterproofing problem, and we will say so rather than board over it.

Seams belong on framing

Not floating in a bay

A lap sealed in the middle of a cavity has nothing solid behind it. Any movement or pressure opens it, and it cannot be inspected properly.

How we run it

Sheets are sized so seams land on a stud or plate, lapped, and sealed against solid backing. It uses slightly more material and it is the difference between a barrier that holds and one that is only continuous on the day it was installed.

Inspection, and leaving it visible

It gets checked before it is covered

Vapour barrier and air sealing in McKernan are inspected before drywall covers them. We sequence to your inspection date rather than boarding ahead and covering something the inspector needs to see.

If it does not pass

We want the inspector's note directly. Most failures are specific — an unsealed box, a floating seam, a torn return — and they are corrected faster from the actual note than from a second-hand summary.

Electrical boxes, the usual failure point

A hole in the plane

Every outlet and switch in an McKernan exterior wall is a cut in the poly. Left unsealed it is a direct path for moist air into the cavity, and the boxes are usually the coldest spot on the wall.

Poly hats and sealant

Boxes get a poly hat or an air-sealed box, and the poly is sealed to it rather than simply cut around. It is a small detail repeated dozens of times, which is exactly why it gets skipped.

Basement walls, where the rules change

Concrete complicates it

A McKernan basement wall can take moisture from the ground as well as from the room. That is why a poly barrier detailed the way it is on an above-grade wall can trap moisture against the concrete instead of keeping it out.

How the assembly is built

Rigid insulation or a framed cavity held off the concrete gives the wall a way to dry, with vapour control on the warm side of the insulation. Getting that order wrong is the most common reason a finished McKernan basement smells musty.

How it works

Simple, clean, on schedule — Vapour Barrier Installation in Mckernan Edmonton

Free quote

We come out to your Mckernan Edmonton property, take a real look at the vapour barrier installation, and hand you a fixed price on the spot — no guessing, no vague ballpark. Every vapour barrier installation quote in Mckernan Edmonton starts with an honest, on-site assessment.

Book a day

We pick a day that works for your schedule and show up on time, ready to start the vapour barrier installation in Mckernan Edmonton. No back-and-forth rescheduling — once it's booked, our team is there.

The work

We keep the dust under control and protect your Mckernan Edmonton home while we finish the vapour barrier installation to a clean, paint-ready standard. Floors covered, doors sealed off, and the site left tidy at the end of every day.

Walk it with you

We don't pack up till you've walked the finished vapour barrier installation with us and you're happy with the result in Mckernan Edmonton. If anything needs a second look, we handle it before we call the job done.

Reviews

Rated by Edmonton Homeowners

★ ★ ★ ★ ★

Emplastrum Drywall is the vapour barrier installation contractor Mckernan Edmonton trusts for repair, restoration and finishing — rated on Google by Edmonton homeowners.

Read the reviews, or leave your own after your vapour barrier installation project in Mckernan Edmonton.

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FAQ — Vapour Barrier Installation McKernan Edmonton

Vapour Barrier Installation McKernan Edmonton: your questions answered

What if there is already a vapour barrier in the wall?: We tie into it, and we check whether there is a second one somewhere that would trap moisture between the two. Older McKernan renovations quite often have both, and finding that before boarding is worth the hour.
Is it a problem to have poly on both sides?: Yes. Two barriers trap moisture between them with no direction to dry. It is a real mistake we still find in renovated McKernan walls, and it stays invisible until the damage shows.
Does it matter where the sheets overlap?: Yes. A lap must land on solid framing and be sealed with acoustical sealant compressed between layers. An unsupported lap taped across a cavity flexes with pressure changes and works loose.
Is the vapour barrier the same as an air barrier?: Not by itself. Poly slows vapour diffusion; sealed properly it also slows air, and unsealed it does very little of either. The sealing is what turns a sheet of plastic into a working assembly.
Why is there staining around my window reveals?: Usually the vapour barrier return at the window was torn or tucked rather than sealed. It is a cold junction, so condensation shows there first — often as staining or mould at the reveal.
Should I use poly or a smart membrane?: Most straightforward McKernan walls are fine with 6-mil poly, continuous and sealed. A variable-permeance membrane is worth it on retrofits and some basement details because it gives the assembly a drying path in both directions.

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Vapour Barrier Installation McKernan Edmonton

Vapour barrier in McKernan, sealed as a continuous plane