space between brick veneer and inside wall necessary?

Hi,

I was wondering if the 1.5" space between the outer brick wall and inside wall was necessary? I have a guy who wants to fill it full of insulation (water-based, foam in place insulation) and he says it won't be a problem to have it filled in. Anyone have any thoughts on this?

 

I'm no bricklayer, but IMO the space should be an empty cavity similar to a rain screen. If there is no space, there can be no drying- moisture absorbed by the mortar will not dry out and the back of your brick facade and possibly your sheathing could be subjected to constant wetting... similar to the moisture/rotting wall disaster that was addressed in the Dec 08 Journal of Light Construction where a cultured stone veneer was placed directly against the sheathing with no air space or drainage plane.

 

Thanks XSleeper,

I get where you're coming from on that. But I'm told that this foam is effectively impermeable to moisture/ water, so it shouldn't allow water to seep through it and reach the wallboard on the other side of the brick. It would more than likely just keep the brick wetter longer...which doesn't sound great, but how damaging could that could really be?

 

Carl -

Where are you located and what is the climate? - That is necessary to get an intellegent response.

Posting everwhere possible it not wise because you will end up getting dis-jointed responses based on many other opinions.

What you are thinking about is a very bad way to jump unless you know the construction of the walls, loaction vapaor barriers, method of attachment of the veneer to the structure and the properties of the foam.

It sounds like you are talking to a foam peddeler. You may also be over-influenced by the trendy "green construction", most of which is really short term and can actually be detrimental to ecology.

There is a good reason for the cavity since it allows a way for moisture coming through the brick veneer to drain. If your house is built properly, you should have a moisture barrier outside of the sheathing.

Adding foam to the cavity could create a vapor barrier, which will trap moisture inside of it, causing rot and mold due to moisture retention. This could be a classic case of a double vapor barrier, which is a recipe for and eventual disaster. The peddler will be long gone before your realize the magnitude of your mistake.

Dick

 

It would seem to me that unless the installer could completely fill the entire drainage plane, everyplace there is a void water penetrating the brick veneer or entering at wall penetrations would pool at atop the insulation at the bottom of each void, rotting out the sheathing, corroding the metal ties that secure the brick veneer to the framing behind it, etc.

 

Dick, much appreciated, am actually in Philadelphia. Didn't mean to put question in multiple spaces, it was just that when I first logged in, I saw some questions that hadn't been answered that seemed to have been there for a while and was just hoping to get it in front of a person who might know about it. The idea of the foam peddler sounds interesting though. I also didn't know about "double vapor barriers" and that that could be a problem...something I'll definitely have to look into. Your answer was very helpful, thank you for the response.

Regards, Carl

 

THanks Michael, hadn't considered that he might not be able to fill it completely. I also can't think of how my installer could truly guarantee that he filled it either, or that it would never seperate or come apart anywhere once inside. The more I think about it the more it seems that I risk a serious moisture/ rot/ mold problem from it long term. Dang, and I thought this foam insulation was going to be a good, easy solution. Thanks a great deal for your help here,

Carl

 

Not a good idea. Spray in foam is used to fill the cores of CMU, not the (engineered) airspace between a masonry veneer and the structural wall.

 

Carl,

I opened a topic about this question over on inspectionnews.com as I'll probably eventually see somebody attempting this in Chicago. So far there are only a few replies, but the consensus seems to be that there are potential problems of the kind noted below in retrofit situations, whereas in new construction it's possible to run the hose all the way down the walls via completely unrestricted access to the drainage plane at the top of the wall, and thus at new construction you have a much better chance of avoiding voids or other flaws the insulation.

As for whether or not a retrofit foam can adequately fill the voids, when you see a brick veneer wall opened (typically, to deal with moisture problems) you will almost always observe various ways in which the drainage plane has been compromised.

Some of it these are inherent in the way brick veneer walls are constructed, some are the result of incorrect building practices and/or carelessness.

For for example you usually observe mortar falling down the drainage plane and compacting at the base of the wall and accumulating atop headers above wall penetrations, obstructing controlled drainage channels such as weeps, you see various kinds of construction debris that has been left by tradesmen or fallen downs down into the void, construction defects such as improperly attached building paper which has fallen off the sheathing, has folded over, and is now collecting additional mortar and debris, and so on - the "drainage plane" is almost never the smooth continuous void depicted the diagrams, rather it's an imperfect separation obstructed here and there, but on the whole draining well enough to "work".

How well retrofit insulation will tightly seal around all these sorts of various imperfections is an open question, and one that I don't think you could answer except by opening a substantial number of walls that have been retrofitted with foam insulation for inspection.

Meanwhile, it might be a number of years before any problems being created today become evident in the form of moisture damage, and by then there is a good chance the insulation contractor will be long gone, even assuming they were willing to assume responsibility for remediating the problem.

 

Veneer masonry walls are not waterproof. The airspace is required to allow moisture to exit the wall at the base through weeps. Any material in the air space (with the exception of ties and mortar deflection devices) will provide unwanted bridging between the masonry and the backup wall. If the wall section is designed for foam, it will utilize foam sheeting, not spray in foam.

 

Hey Michael,

Carl here, I hadn't even considered that there could be debris in that space that could hamper the foam's ability to flow into every gap and fill it. The idea of a "bridge" occuring within that space that allows moisture to cross to my interior wall is not something I want to deal with down the road. I can't even imagine how big of a problem that would be to fix if the outer part of my interior walls started to rot or get moldy...would probably have to tear out all the interior dry wall to get access to it...yeesh...can't wait to see what my foam contractor has to say about this. Can't really see a point in moving forward with this project at this point.

Thanks again Michael, you might have just saved me from some enormous problems down the road from going with this stuff.