Wood-framed wall waterproofing

[Alan CA]

Hi everyone,

Does wood-framed wall assembly required waterproofing membrane?

Some argue that the air barrier will provide water-tightness. However, the effect of this barrier waterproofing efficiency is debated, if not refuted.
Some others argue that the sheathing grade plywood glue is water-resistant. However, we see the otherwise especially after being subjected to fire-fighters water.

If you see the wood-framed wall assemblies in the majority of the wood construction books, waterproofing memranes are not mentioned or shown in the details.

What do you think? Thoughts are highly appreciated.

 

[jayrod12]

If you ask our building envelope department, 100%. And from the amount of ridiculously rotted wood walls I've had to repair I would tend to agree with them. But whatever system you go with it needs to be vapour permeable and a whole bunch of other details that are super important. Rain screened walls are become super popular for our building envelope upgrade jobs.

Also, even though they say waterproof glue, plywood will rot if subjected to water long enough, and OSB rots just thinking about getting wet. In the old days where buildings weren't super tight the natural draftiness would dry stuff out preventing damage. Now, with all the attention to sealing windows, doors, vapour barriers etc. The wood doesn't get a chance to dry out when water does infiltrate. So then it sits and rots away at the wood and grows some serious mold.

I've seen more than a dozen houses that are less than 10 years old require complete re-cladding because of shitty window and waterproofing details causing water infiltration and rot. So much for your million dollar home when you need to spend almost 100K recladding it within 10 years of the build date.

 

[Alan CA]

Thank you for your answer, Jayrod12. So, do I understand that you arr with adding a waterproofing membrane on the sheathing of the exterior walls?

 

[jayrod12]

Yes, but again, there's much to consider. It needs to be a vapor permeable water barrier. It can be a peel and stick product or a roll on type product, but the vapor permeable is a must.

 

[Canuck65]

If you put a true waterproofing membrane on the exterior sheathing in Ontario, you are asking for trouble down the road. Jayrod is correct that whatever is used must be vapour permeable. Do not rely the glue for the plywood being resistant to deterioration, that is nonsense. Full marine grade or preservative foundation wall treated plywood can resist deterioration due to moisture, but I have never heard of it being used for above grade wall sheathing. Look in Part 9 of the Ontario Building Code and it will guide you to the suitable materials.

99%+ residential wood framed buildings constructed in Ontario use an air barrier (Typar or equivalent) on the exterior sheathing. That combined with some waterproof flashings at critical junctures and designed as a rain screen will give satisfactory performance. Look up the CMHC Best Practices Guides, they have good background information suitable for northern climates.

On a side note, normal Ontario construction has a vapour retarder on the interior (warm) side. A number of years back I was taking some building science courses from some very high level building scientists who provided input to the OBC. They were advocating for an air barrier on the exterior and on the interior of the walls(in place of the vapour retarder). More and more often, with the use of air conditioning, they are seeing the typical vapour drive move towards the interior during the summer, resulting in condensation on the face of the vapour barrier behind the drywall. Lots of mold and rot behind the drywall. It's not codified yet, but something to watch out for.

 

[jayrod12]

....will give satisfactory performance.

In my experience, not often anymore. It's sad, but the attention to details of flashings etc is so poor that this type of construction just isn't holding up.

 

[Alan CA]

Thank you Canuck for your input. I have two points to comment on:

1. I agree that we rely on the air barrier to 'limit' the water infiltration. However, the air barrier limits but doesn't give full waterproofing performance. And here's where my question rises.

2. I have reservations on the double air barrier layers (i.e., on the interior and exterior). This is similar to the delimma I'm inquiring about, in this post, as some water will find its way through the wall. With 2 air barriers, water will find it hard to escape and molding and rotting will be imminent.

Therefore, 1 vapour with air barriers will not be 100% waterproof, but 2 vapour barriers (or 1 vapour barrier and waterproofing) will cause water to trap. It's a dilemma, I I know!

 

[jayrod12]

That's why I stressed any barrier applied to the outside needs to be vapour permeable. and homewrap (tyvek/typar) does not count as a water barrier. At least not to the building envelope guys at our office.

 

[Alan CA]

I agrer Jayrod. Air barrier must be vapour barrier. And I agree rhat Tyvek is both vapour and moisture permeable. This is an issue.
Still I find it an issue that we can't put waterproofing membrane to avoid trapping moisture. This is both required and weird to me.

 

[Canuck65]

If you put a vapour retarder (vapour barrier or waterproofing membrane) on both the interior and exterior, the building envelope will fail (in Northern climates like Ontario). Right now the Code accepted practice, when executed correctly, is to have a vapour retarder (6 mil poly) on the warm side and an air barrier (Tyvek/typar) on the exterior. It works, and it works well ... if executed properly. Don't change the a tried and true assembly because of poor execution by contractors. Advocate for better construction practices and more fees for construction review by professionals during construction so that the crap we sometimes encounter (and I have seen my fair share) is minimized.

 

[JoshPlumSE]

2. I have reservations on the double air barrier layers (i.e., on the interior and exterior). This is similar to the delimma I'm inquiring about, in this post, as some water will find its way through the wall. With 2 air barriers, water will find it hard to escape and molding and rotting will be imminent.

I saw a similar situation once very early in my career. I was interning at a company that did a lot of "building envelope" related work. Anyway, there was an indoor pool with some consideration to vapor and /or water barriers on each side of the wall. But, in certain conditions (that ended up being pretty common) the "dew point" ended up being inside the wall between the two barriers... This resulted in very quick (but hidden) deterioration of the wall and structure.

Note: I'm not an expert on this subject. I only an intern there for one summer. I learned some. Enough to empathize with your concerns. But, not enough to know the proper solution.

That company no longer exists, but some of those folks went on to the company below. Eugene Buick and Gerson Bers were the people I interacted with. This is the type of company that can more comprehensively answer your question....

https://www.abbae.com/

 

[Alan CA]

Thank you for your input, Josh. Tbis is what I was trying to explain to Canuck. I'm neithrr an expert on the matter but I encountrr such situations at some projects. Some insulation companies warn about the double vapour barriers (interior and exterior). However, I think what I've overlooked in Canuck's idea is the Tyvek material. Tyvek can breathe. It's not 100% impermeable so I think it would allow ttapped vapout out. The bad mistake, in my opinion, is that if both vapour barriers are real effjcient barriers.

 

[dik]

You simply have to have a means for 'trapped' moisture to get out... I recall some horror stories, earlier on, about some EIFS buildings out on the west coast.

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

 

[Alan CA]

I agree, dik