attatching stone veneer to cinder block
hello all. new to the forum. looks like a great place for great info!
ive got a question. i have a house with a cinder block basement, and on the outside, its been parged. the parging looks ok but we would like to cover it with stone veneer. the problem is that there is a slight amount of effloescence coming out through the parging. as i dont want to inhibit the evaporation of this, i was thinking of putting strapping or vertical slats of cement board, then attatch full sheets of cement board to put the veneer on. that way, it would provide an air gap to allow breathing, but give me the look i want.
wondering what you guys have to say about that idea, and if there is a solution that i dont see or have not thought of. i am in no way a home builder, just a handy diy’er who tries to do everything by code or better. i usually tend to build things way overkill, but thats the way i prefer it.
thanks
clarence
Replies
You may want to read this on efflorescence before starting your project. http://www.gobrick.com/portals/25/docs/technical%20notes/tn23a.pdf
It's not something you want to continue encouraging or facilitating.
It usually is an indicator of a moisture or drainage problem. IMO, your plan sounds like alot of extra material resulting in little to no gain...or actually an excerbation of existing problem. Also, you will probably want to follow the manufacturer's recommendation for application of stone veneer (whatever that may be) for warranty purposes. Most manufacturer's are very good at giving guidance on best practices.
Cheers!
What you are proposing is a rainscreen and that is a good thing. No matter the underlying reasons for the efflourescence, the rainscreen won't do any more harm and could actually improve the situation. Use pressure treated wood for the strapping. You might also want to install bug screening at top and bottom depending on your particular situation. I didn't do it on my house but my rainscreen is open joint so screens would be pretty impossible. Besides, nurturing spiders is really not a bad thing. Hornets on the other hand......
The application of the new stone veneer depends on the attachment to the new cement board only. What the board is attached to is irrelevent.
How would a masonry veneer w/ a rain screen "actulally improve the situation" of efflorerscence on a parged cinder block foundation?
My understanding of the main cause of efflorescence is vapor drive (wet materials trying to equilibrate toward dry). The exisitng foundation's exterior exposure to dry air is already at it's maximum. In other words it cannot possibly be any more enhanced by a veneer covering--even with a rain screen.
My guess is the cinderblock foundation is wicking up excess ground moisture due to high permability of existing foundation and then attempting to release this moisture at drier, above grade, conditions. The reasons for high permability could be multitude; including (but not limited to):
1. cracks in CMU wall
2. compromised parge coating
3. lack of positive drainge away from foundation
4. lack of positive footing drainage.
5. lack of capillary break between grade and foundation
I'd recommend have a local foundation drainage professional review your home's conditions to identify the cause of the efflorescence before choosing to add another layer of material to your home's exiisting foundation. It will probably be well worth the cost of the consultation before proceeding.
Of course, if you don't care about excessive moisture in your foundation and/or basement (and the trouble it can cause), then push on forward with your stone veneer. The additional pressure treated furring, cement board, and stone veneer certainly won't care about the moisture...at least for another 20-30 years or so.
Cheers!
Deadnuts, when you say capillary break, what are you referring to? Like the block or parging is wicking moisture up from the ground? And if so, how does one go about correcting this if it is this? Also, is there a way to know that's what is causing it?
Thanks for your input.
Clarence
Thanks guys. Appreciated. I have to add that the area we live in is all sand and that moisture shouldn't be a problem. The efflorescence is very slight. I understand what you are saying about correcting it, but I felt it was such a small amount, that it would be ok. The house was built in '78 and has never flooded in he basement, and doesn't have any cracking of the blocks or joints. There was a black tar type material that was put on the block that goes roughly 4" above grade. On the inside of the basement, it has been bare wall since it was built, and I recently (2 years ago) installed 2" xps on the walls top to bottom. Before I did that, there were no signs of efflorescence on the walls inside. I have thought of taking the parking off, but thought of using cement board strapping to allow the block to breathe since it can't breathe to the inside because of the insulation.
Clarence
Ok, just read the link you gave, and it makes sense to me. But in reading that, looking at the picture in it of the brick veneer they posted, it looks like the same idea I want to do. Basically making a air gap to allow the water to leave. I will also note that there are other areas of my foundation in the back that are not parged, and there is no efflorescence on there. So maybe it's coming from the parging and the moisture it holds?
clarence
consider and limit your waterproofing "weak links"
Clarence,
It could be salts in the masonry cement used to parge your walls...or It could be salts in the ground water/moisture being wicked by your foundation. Who knows? Thats why I recommended you consult with a local foundation waterproofing professional.
Bottom line is your concrete block foundation is pourous (hygroscopic in nature in that it sucks moisture like a sponge) and is acting as a conduit for moisture to travel from wet to dry. In order to break this conduction of moisture, you should have a continuous waterproof capillary break at all areas of your home that are exposed to ground and rain water. Capillary breaks come in many forms which include moisture and vapor barriers. They range from applied liquid latex "paints" and asphaltum tars to sheet polyethelyne waterproof films and drainboards. Personally, I like to use Schluter's Kerdi sheet (1st capillary break) to waterproof the exterior foundation walls of my homes and additions. If my foundation also has a basement where I need to direct liquid water away from the house, then I also apply a geo fabric lined drainboard (2nd capillary break) up against the Kerid which allows ground or surface draining moisture to easily seperate itself from the soil and be directed to positive drainage away from the house.
The tar you have on your foundation is probably "damp proofing", not waterproofing. While It is considered a capilary break, it is not a water proof barrier. It is common for moisture to penetrate this liquid applied film and travel within the masonry wall and exist at drier areas that are uncoated (like your exposed parging above grade). Gravel under a slab is also considered a capillary break--but ceases to become one as soon as it is completly submersed in liquid water. That is why it is usually used in conjunction with polyethlyene sheeting which can form a moisture proof capillary break under slabs and at footings which are subsceptible to wicking ground moisture
This excerpt is from a previous Green Building Advisor thread might also help with understanding and function of a capillary break:
"A concrete block foundation is no different from a poured concrete foundation in terms of wicking ability. If there is any possibility of moisture in the ground and you want a dry basement, then a capillary break should be installed between footings and walls, on the outside of foundation walls, at the wall/sill interface, and between the walls/footings and the slab (in addition to a thermal break)."
Answered by Riversong
Posted Sat, 05/29/2010 - 12:03
Lastly, the brick in the article link I posted is supported by an extended footing. This brick can be laid with a continous capillary break from the footing all the way up the main foundaiton bearing wall. This may be what you want to do, but my guess is that you don't have an extented footing in place to provide the same ease of support and continuous capillary break. You're going to have to be more creative in trying to eliminate moisture penetration in your veneering approach which requires you to attach directly to your main foundation wall. In other words, each place you attach your veneer support to your house becomes a weak link in your waterproofing/capillary break chain. My advice is limit the weak links.
Note: Attaching a bunch of furring strips through your exising parging and asphaltum tar foundation coating does not accomplish that goal very easily.
More information?
First, what part of the country are you from? Climate, humitity etc might play a role.
How old is the foundation? If it's new, the efflorescence could be just the result of the block drying out. If it's older, there is some moisture being pulled thru the wall....could be from the surrounding grade, landscape irrigation, excessive humitiy in the basement, etc.
Is there any paint on the parged surface?
Given what information you have provided so far and assuming the parging is in good condition and well adhered to the block, I would clean and roughen up the parged surface and apply the stove veneer directly to the block wall.
I think the idea of installing wood strapping and cement board is a very bad idea and I don't see any value..I see many potential problems - moisture accumulating in the voids, all the fastners that could fail due to rust, waterproofing the top of the voids, etc.
The block is a perfect surface for installing the veneer - I don't see this being any different from placing rock veneer on the outside of a masonry chimney...they are notorious for effloresence and I've never had a problem or issue affecting the adhesion of the veneer or long term efflorescence issues...
we are in southern manitoba, canada. its not really humid here right now. and the house was built in '78. the parging looks like its adhered pretty good. i realize i could just use mortar with maybe a bit of thinset to stick the veneer on, but my whole reason for asking about this, and trying to come up with a better solution, was so that when i put the veneer on, i was scared that the efflorescence would eventually come through and stain my veneer. maybe i should stop overthinking it, and just put it over the parging? dont know.
i know what the RIGHT thing to do is. i would excavate all the way down to the footing, then apply blueskin to the whole foundation wall. but, i dont have the money to do that.
thanks for the replies
clarence
blowin' smoke
Sounds like you’re not looking for " a better solution" so much as a cheap solution. The original post indicated that you “usually tend to build things way overkill, but that’s the way I prefer it.” What a bunch of smoke.
If you knew what you should be doing all along (Blue Skin is a rubberized waterproofing capillary break membrane similar to Kerdi's orange polyethelyene version) , then I suggest amending your original post to reflect your insincerity. You're basically someone that wants to add a high end exterior finish, but is apparently too cheap to do it right.
Go ahead; slap some lipstick on that pig. But remember, It'll still be a pig.
Type of Veneer?
I should have asked about this as well earlier...what material are you thinking of using? The concrete 'stone' type, river rock, flagstone, blue stone, etc?
If you were using a stone that could be stacked and semi self supported (like brick), then you could install it like a bick veneer. Since you don't have a ledge built into the block wall, you could install a steel angle at the base of the veneer and build the veneer on top. This would allow an air space between the veneer and the block wall. The installation of weep holes at the base of the veneer would any drainage. You could use metal ties between the wall and the mortar joints to help support the wall... However, this will result in a relatively thick veneer and may cause other problems around openings, corners, etc. It will also require some sort of upper sloping cap (precast concrete?)
If it's a material more suited to be applied with mortar/thinset, than that's how I would put it up... In this case, you may be overthinking the issue..especially if it's a minor amount of efflorescence. I think the other option you listed raises too many other issues and potential problems.
I had something like this happen a few years ago. It was a concrete foundation with a stucco veneer over the top...the stucco extended down a ways over the concrete from the wood frame walls above. It turned out to be the irrigation sprinkers were the source of the water causing the efflorescence on the stucco,,
Gee, thanks nuts. Like I said above, I'm just an average DIY'er. Not some huge contractor with tons of money. I'm not here to get info on how to do it the fastest, cheapest way possible so I can flip the friggin thing. And, sometimes the most expensive way is not the only way. Hence the reason I asked for other opinions, which you gave. Thanks for your useful posts. I'm new here, so not as experienced as you obviously. I don't have a problem of water or leakage into my basement, so I WAS trying to avoid digging up my whole yard to put waterproofing in.
Clarence