Getting closer to breaking ground on a new house here in north GA. GC is building it to specs that require (as does our contract) that he follow Lstiburek’s guidelines for the Mixed Humid Climate here. Will be brick veneer. No problem with him meeting the rain-screen requirements (52″ annual rainfall) with appropriate materials.
But what’s still worrying me is keeping the mortar droppings out of the air space behind the bricks. If that space is blocked with mortar, it’s not gonna function right. So, should I suggest he use Mortar Net, or a similar product? (Remember, all you craftsmen here, the brick work is likely going to be done by folks less skilled and less careful than yourselves. Perhaps a marginally trained, mobile workforce.)
Replies
You can't keep mortar droppings out of the airspace, but Mortar Net (there are others that are similar in function) will keep the weep holes clear.
What you want is at least a 1" airspace so mortar that is squeezed out when the brick is laid won't bridge over the cavity.
I guess what I'd been reading about was the concern about droppings blocking the lowest weep holes, since they'd accumulate at that level. I get what you're saying about the squeezed mortar; hadn't thought about that.
What's a motar net? Is that anything like a snipe net?
IMO, if you want to maintain the airspace you should apply foam insulation of the proper thickness before the brick is layed.
Edited 10/15/2007 11:22 am ET by Hudson Valley Carpenter
It's different; we got lots of snipes here and the proper nets for 'em too.http://www.mortarnet.com/mnoverview.htm
Oh, the entire house will be Icynened, but since that goes between the exterior sheathing and the drywall you still got "brick layers" slinging mortar around in that exterior cavity.
"Oh, the entire house will be Icynened, but since that goes between the exterior sheathing and the drywall you still got "brick layers" slinging mortar around in that exterior cavity."
OK but may I bring your attention to the Motar Net link in your previous post. The artist's drawing shows foam insulation in the cavity, although not as a solution to the problem they seem to address with their product.
I have to admit that I've become a little skeptical, some might say a curmudgeon, about new products which purport to solve an imagined problem but end up being permanently hidden before their efficacy can be determined.
"OK but may I bring your attention to the Motar Net link in your previous post. The artist's drawing shows foam insulation in the cavity, although not as a solution to the problem they seem to address with their product."
They're showing the rigid insulation on the outside of a CMU wall - easiest way to insulate that type of wall.
We spec Mortar Net for brick veneer over DensGlass Gold sheathing all the time - all insulation is in the stud cavities. No problems to date.
Mtnboy
You are overthinking things.. morter dropping will not provide a solid water proof barrier.. they simply won't .
Proof? Well I can take a poured wall, use a vibrator and still the wall will leak ground water if not given a protective barrier coating before it's covered back over..
Now think about the odd mortor droppings and the chance that they will seal an area off completely.. virtually non-existant..
If I were really concerned I might put some wire mesh such as a coarse steel wool pad around the cotton wicks. If the thought of rust streaks keeps you awake they make bronze wool that will do the same thing.. I bought mine at my local hardware store..
You are overthinking things.. morter dropping will not provide a solid water proof barrier.. they simply won't .
I couldn't agree more, but it will plug the weep holes enough to become a major problem, particularly in areas that have rapid temperature swings. I ahve seen it happen and in older homes that were built without a brick drop in the foundation you end up with rot problems. Most of those homes also have improperly installed flashing behind the the brick, but that is a seperate issue. Anything that reduces or limits the accumlation of mortar droppings at the weephole level is good.
I have had archys spec all kinds of methods and product to avoid that problem on commercial jobs. Getting the brickies to do any of them was always a problem. Mortar net is simple enough to solve both issues, or at least give him a little advantage in solving a reccuring problem.
Dave
Dave
I suppose I've spent as much time up on scaffolding here as anybody. In the early days that's where I needed to go to sell my forklifts.. as they became standard I could meet them on the ground easier.. But about that time I started to do the stone work at my place.. In all those years I've seldom seen enough mortor at the base to block anything.. What I Like to see happen is the cotton rope that is used to form weep holes stapled up along the wall and a chunk of bronze wool stapled over it..
That cotton rope wicks out any moisture untill it rots and then the bronze wool prevents insects etc. from getting in. it also gives water another access path to the cotton rope.
Now I admit I've seen my share of corner cutters who use steel wool instead of bronze wool to shave a few cents, BUt anal me worries that rust stains mught some day result and also not do a good job of keeping out insects..
Ditto the scafold experience.
I've also cut to many new patio doors into existing brick veneer homes to know that the mortar droppings behind the brick can reach as high as two or three coarses. More than enough to impede the movement of water to weep holes or even the rope wicks. Couple that with the moisture wicking into any torn flashing, felt paper or exposed wood and you get a real mess. I would guess that on average 50% of the door installs I've done have also had some rot or water damage repair that became an additional cost to the HO. Not a good percentage IMO.
Maybe you your breed of brick layers are a cut above what we have.
For my money the mortar net is cheap insurance.
Dave
Dave
Dave,
I certainly don't have that level of experiance tearing into constructed masonary works. I just wonder what caused the water retention. Morter is lousy at holding water and mortor that isn't struck and slicked would be even worse at it..
It is not ther retention that is the problem, but the direction the moisture takes as it tries to get to the lowest point on the wall.
Dave
Dave,
Your last post has me intrigued.. I hope you don't feel I'm being argumentative. I'm not trying to be.. You mentioned in an earlier post that a high percentage of walls you opened up had rot issues and I'm trying to understand why.. I'm assuming that they were properly wrapped with felt paper etc.. so that isn't the issue. You seemed to indicate that is was because of mortar droppings and that has me puzzled..
I understand how water gets behind brick and stone work.. even assuming a good job done on flashing and caulking. What I don't understand is how it could not find the wicking/weep holes. As I said your last post has me intrigued. Are you suggesting that enough moisture could be retained in some locations to cause problems? trapped between the felt and the stone/brick in a pool?
That somehow dropped mortar was able to retain the water/moisture long enough to do damage?
That's the part I don't understand.. cement (which I like to think of as just mortar with some stones in it) when poured into a form and vibrated carefully to remove all air pockets still cannot hold out water but requires some sort of membrane installed to do the job. While the odd droppings of mortar can fall and do a perfect seal long enough to soak thru felt and damage wood..
I suspect I've not seen enough wood rot behind stone work/brickwork to really understand the process. Or perhaps our locations are differant enough that it's more common in your location?
Many of the house I have worked on are of the late sixties to early eiighties. Moderat to smaller sizes and built by production builders of the era.
This is no knock on those builders. They were building homes to meet the demand of the time and trying to maximize profit in a very competative market.
Foundations were 8" poured or block with no brick drops with standard stick framing setting on top. Exterior sheeting ranged from plywood corners with celotex being the balance, to a flimzy foil faced board with let in corner braces. Sheathing board seldom ran down to the mud sill. It stopped on top of the joist and the bottom flashing for the brick was lapped up the joist and under the sheathing board. On higher end home the builder might have then used felt paper over the sheathing, but on most homes that was time and money better kept.
Now you have a 2x4 framed wall seting on 2x8 or 2x10 joist, setting on and untreated 2x4 mud sill with a piece of black 6 mil plastic 16" tall, protecting everything. Fill that bottom 10" of cavity behind the brick with mortar, bridge it a few more places, and throw in some poor or missing head flashings around the home, and you have a disaster waiting to happen. Weep holes plugged, wind driven rain, and maybe a sudden freeze and you now have a lot of moisture trapped behind the brick. Repeat that cycle over a few years and rott/mold is a given.
That is what I found in homes that had problems. On those that didn't have problems, the salvation was in felt paper, good flashing details, and just dumb luck sometimes.
Good brick layers in a competative market are hard to find. Mudslinger or brickie pretyy much coverd that topic. Back in the 70's brick was $90 to $120 per thousand. The mason only got about $25 to $35 a thousand in labor. You gotta "slam some brick" to make any wage at those rates.
As a Remodeling contractor back then, I made a decent living fixing and repairing a lot of those homes. I didn't know squate about building science, nor did many of the builders. We just did what we always did, untill something went terribly wrong or someone found a more profitable and better way to do something. That just didn't seem to happen very fast with the masonry trade.
Dave
Here is something else to think about - maybe even more important: You want your weep holes at least 1 course below the lowest wood that is going behind the brick veneer.
Take a look around this web site: http://bia.org/html/frmset_thnt.htm
Start by looking at documents 7 and 7b. It should help.
Edited 10/15/2007 8:50 pm ET by Matt
Thanks. I bookmarked it; will read tomorrow when my eyes (and brain) are working better.
Just finished reading the BIA guidelines. In 7B they say that the use of a product like MortarNet does not guarantee that the air space will not be bridged by mortar droppings. And that the real prevention is to minimize mortar droppings. So, there is no magic cure; just do it right in the first place. And, of course, BIA describes exactly how to do that.I suppose that I just discuss this with my GC and put some more words in our contract (not yet executed) governing how the brick is to be done. Okay, saves me $$. GC always grabs the language from his contracts with homeowners and puts it into his contracts with his subs. So, that's the way I guess it oughtta be done.I'll forget the MortarNet and beef up the contract and go visit onsite when the brickwork starts. Anybody wanna stop me now, as they say?
MtnBoy,
As a bricklayer, I think Mortar Net is a good product. A bricklayer can lay up veneer without dropping mortar in the airspace, just as a painter can paint all day with very few drips. But even a very skilled painter finds it prudent to use a drop cloth. In a similar manner, Mortar Net provides an extra layer of protection. Water will go past the occasional mortar bridge. It won't get through the weep hole if the bottom of the air space is clogged with mortar.
This is an irreversible situation; once mortar drops in the channel, it can't be removed. You also have the problem of monitoring the work. Without standing there watching them all day, how can you be sure that the masons are taking the care to insure that no mortar ends up in the space?
I can only add that I'd use Mortar Net on my own house.
OK, so I guess you've convinced me to be back to using MortarNet. You being a credible source. (You're not selling MortarNet are you??)I wonder why BIA would say there's no guarantee that you still won't get clogged weepholes? Or whatever I quoted from them in my recent post--I printed it out, but have forgotten at the moment and filed my copy away. One other question: I don't know how skilled some of our local workforce here is. Think their supervisor could quickly train them (and there may be a language gap here) to use MortarNet? Just by showing them? I guess the actual product name is HouseNet. Their website doesn't make it real clear.Thanks for your help.
OK, so I guess you've convinced me to be back to using MortarNet. You being a credible source. (You're not selling MortarNet are you??)
No, I'm not selling Mortar Net. I think it is a good product because it provides a realistic system for draining cavity walls. Engineers and other designers often think up optimal systems. Unfortunately, many of these systems are just about unbuildable--especially if you factor in the actual (as opposed to the ideal) labor force that will do the work.
There's no doubt that a cavity free of mortar droppings is ideal. Any water that gets past the bricks runs down the inside face of the wythe of bricks and exits via the weep hole. The water cannot jump across a 1 or 2-in. gap.
The only problem is that the people who are actually laying the bricks are under daily pressure to lay as many bricks as they can. This pressure begins with the owner, who wants the best price he can get. It goes through the brick contractor, who wants to maximize profits. And it ends up with the guy actually setting the bricks in the wall. If he wants to keep his job and get a raise once in a while, he has to produce.
Bricklayers develop habits that maximize the number of bricks they lay per day. Some bricklayers also develop habits that result in very neat and handsome work. I've heard some bricklayers brag about how many bricks they can lay in a day. I've also seen people lavish praise on the "artistry" of a given mason. I have never in my life heard anyone say: "man, that guy really lays a waterproof wall."
Although most bricklayers are trained to be as productive as possible, a bricklayer can develop troweling techniques that limit the amount of mortar that drops in the cavity behind the bricks. But make no mistake, there is a price in productivity to be paid for this kind of work. It is a little like the sider who seals the end of every cut. It throws off the rythm and is a drag on productivity.
It's up to you to find a bricklayer who has made this adjustment in his troweling techniques. Keep in mind that this is hard to police and impossible to fix (short of tearing out the brickwork) after the fact. But even the best bricklayer will drop mortar occasionally. It is as unrealistic to ask a bricklayer to have no mortar droppings as it would be to ask a painter to have no drips. The Mortar Net and similar products recognize that some mortar will inevitably drop behind the veneer. The Mortar Net holds those droppings above the weep holes and, because of its offset pattern, insures that the water doesn't get trapped. (If the Mortar Net just went straight across, a dam created by mortar above it is feasible.)
My advice is to shop around for the right brick mason, be prepared to pay more for a mason who does his best to keep mortar droppings to a minimum, and use Mortar Net.
Mudslinger,
Explain to me if you will why use a cavity wall at all.
I mean I'll grant that water can and does get past the brick or stone.. however once it does why not allow it to exit the same way it came in? I admit my place has a cavity wall with weep holes but In my case it was pure monkey see and monkey (me) do.
I'm just thinking out loud here.. Imagine you put brick or stone on a ICF wall. Would you still put a cavity behind it? I'm certain the foam won't rot if water entered
Explain to me if you will why use a cavity wall at all.
I mean I'll grant that water can and does get past the brick or stone.. however once it does why not allow it to exit the same way it came in?
Frenchy, there are two good reasons unrelated to water to use a cavity:
1.) it's required by code
2.) it prevents problems created by differential movement between the wood frame and brick veneer
However, water is the main reason to put a cavity between the brick veneer and the wall. Water that enters a crack in the masonry or a failed caulk joint can't always "exit the same way it came in." Gravity pulls it down and, once down it doesn't run uphill--as every plumber knows. It's good to have a way to drain it out the bottom.
It's also always good to keep masonry from direct contact with untreated wood. Even when the masonry is not drenching wet, it can stay damp for long periods. This does no harm to the masonry. But when the moisture in the masonry is in contact with the cellulose in the wood, termites, carpenter ants and the organisms that cause rot live large.
Good enough for me. I considered myself well-advised and will spec MortarNet. Thanks for educating me. And I do know the bind created by production pressures.
Dang, your're pretty articulate for a bricklayer!
You said: >> I suppose that I just discuss this with my GC and put some more words in our contract (not yet executed) governing how the brick is to be done. Okay, saves me $$. GC always grabs the language from his contracts with homeowners and puts it into his contracts with his subs. So, that's the way I guess it oughtta be done. <<
Not sure how this is going to save you $$. The more stipulations you want included in the contract, the more you are going to have to pay. Let me also say that you can go overboard with this kind of stuff which could run up a red flag with the builder, if for example, he thinks you are going to be trying to manage the bricklaying process. If you want the Mortar net or a similar product used, that should be specified.
As far as going overboard, BT is a good place to pick up a lot of good ideas but also a lot of "over the top" stuff - so take what you read here with a grain of salt.
kind of off topic, but based on today's activities here is something else: Specify that the steel lentils be painted before they are installed. Most steel suppliers deliver their product with a "shop coat" of red oxide primer. Unfortunately, I think the standard in the residential construction industry is to install the primed (with possibly newly cut ends) lentil, brick it in, then the painter comes later and paints the exposed areas only. Not good - if, after a number of years, the lentil starts rusting it can actually expand enough to start cracking up the veneer. Even a quick Rustolium (sp?) spray paint job is much better than just the shop primer. Problem is, the painter isn't going to make a trip over there just to paint some lentils.
Also BTW - there needs to be weep holes (and flashing) above the lentils.
Thanks. I'm getting this all down. Nice to have a printer working.