Products: Cultured Stone® by Boral® and Boral® Prostone®
Answered by Chris Hines – Technical Manager, Boral Stone Products
Q: Is a Weep Screed a code requirement?
A: The answer is a little grey. It depends on which building code your jurisdiction is working from. As a general rule, anyone working from a building code created in 2009, or more recent, it would be a code requirement on a framed application. And that would apply to wood framed or metal framed. In a masonry application, weep screed is not required.
Q: Can I install #15 felt over Tyvek?
A: Tyvek is a branded house rep product, that is just one type of WRB. Tyvek, #15 felt, grade D building paper… all are types of WRB. We require two; you get to choose which. And there are different performance characteristics for each type of WRB, and they may apply to your climate, or your specific building type. So yes, you can install #15 over Tyvek.
Q: Can I install Cultured Stone® over cement board?
A: This is an evolving installation technique that is designed to remove the steps of lath and scratch coat. Cement board may be used in place of lath and scratch coat, if desired. When used, cement board must comply with ASTM C1325. They must also be evaluated for interior or exterior use in accordance with ICC-ES AC376 based on the desired applications. When using cement board, only modified mortars complying with ANSI A118.4 or ANSI A118.15 should be used as the setting bed mortar. Do not use conventional mortars (Type S or N) with cement board installations. Refer to ASTM C1780 and manufacturer recommendations for additional details on cement board installations.
Q: Can I use Cultured Stone® in a tight-fit application, in freeze/thaw climates?
A: The key to good performance in both tight-fit and grouted installations, in any freeze/thaw climate, is proper thickness and coverage of mortar setting bed. You don’t want to leave voids in the installation, where water can be trapped, and wreak havoc on the installation. So yes, it can be used in a tight-fit installations, in freeze/thaw climates, provided you install it properly.
Q: How much clearance is required below Cultured Stone®?
A: This is probably our most common question. It’s an adhered veneer system, and the building code actually has regulations that specify a 4” clearance from grade, if it’s earth, and a 2” clearance from grade if it’s a paved surface. Our trade association has worked hard to provide a few alternate installations, where you can reduce that amount of clearance to a 1/2 an inch. You have to refer to the MVMA installation Guide to get those details.
Q: Can I seal Cultured Stone® with XYZ brand sealer?
A: We don’t actually believe that you need to seal Cultured Stone®. In fact, it’s probably better if you don’t. However, we recognize there are applications where you may want to make the stone easier to clean. For example, around a fireplace; an application in a restaurant food preparation area. Those areas it makes sense to seal. And if you do, use a Silane-based breathable sealer. So beyond that, I would think long and hard about sealing. There are actually bad things that can happen. For example, you can have efflorescence occur because you sealed it. You can prevent drying to the exterior, and end up with moisture problems. In extreme cases, you can actually end up with spalling that occurs.
Q: Can I clean Cultured Stone® with XYZ cleaner?
A: Our installation instructions have a very generic, “Clean with a granulated detergent.” Basically all we’re suggesting you clean off is dirt or debris. If you’ve got mortar stains from your installation, that you did not remove before the mortar was cured, we don’t have a solution for that. Detergents are not going to fix that. But a granulated detergent, a soft bristle brush, and lots of water.
Q: Can I install Cultured Stone® using thin-set?
A: Thin-set is a polymer-modified mortar product that was developed for the tile industry. And as the name would describe, it’s a very thin application. Our stone requires a thick application. In the previous video you saw the texture on the back of the stone. Thin mortar is not going to fill those voids. And today, many manufacturers offer polymer-modified mortars that give you the best features of thin-set, and the best features of standard mortar.
Q: How can I eliminate, or remove efflorescence?
A: Efflorescence is, by the most simplistic term, a salt. And it comes from masonry materials, mortar products. Water gets into the system. The water soluable salts are then carried to the surface with the water, the water evaporates, the salt crystal is left on the surface; and that’s what efflorescence is. Sometimes it’s white, brown, yellow… it’s a crystal. The best thing you can do is prevent it from occurring. And the keys to that are:
Use high quality masonry materials. Most have integral components that help tie up those salts, so they can’t be absorbed by the water. Mortar products; same thing.
Second, if you manage water properly, and do not allow water to pentrate the system, and saturate it all the time, you’re also going to cut away one of those main requirements for efflorescence to occur.
The final influence that you can have over efflorescence has to do with environmental conditions. And in exterior applications, you have no control over that. If you do get efflorescence, you can clean it with a soft bristle brush, and a 5-to-1 mixture of vinegar and water. There are many cleaners that are on the market that are intended to do the same thing. Many have harsh acids and other things that can affect the colour and performance of our products, so we stick to that simple vinegar and water solution to remove efflorescence.
Q: Can I install Cultured Stone® on my stair-risers?
A: If you’re not familiar with that term, that’s the part of the stairs you would kick, on the way up it. And in many stone applications, you find folks are trying to dress up stairs. And they install Cultured Stone® right down to the stair tread. There are two reasons why this is a problem. We talked earlier about the clearance requirements for Cultured Stone®. And if you install stone directly down to a stair tread, you’re going to violate those clearance requirements. Second, stairs are a great place to use de-icing chemicals. And our product is not going to perfom well if you allow de-icing chemicals to come in contact with it. So stair risers, possible, but it’s difficult to get good performance. I would advise against that.
Q: How high can Cultured Stone® be installed?
A: This is a pretty common question. It comes from old verbage in building code, that had a 30 foot limitation on adhered veneers. Today we still use 30 foot, plus an additional 8 foot for a gable end, in residential construction, and light commercial construction. You can certainly install stone much higher than that. However, all of our testing, all of our evaluation reports, are based on that first 30 to 38 feet. The installation technique, when you go higher than that, typically doesn’t change. It’s just a matter of an architect or designer doing the review, to make sure the product will perform, given the loads it will be exposed to; and by loads I mean wind loads, seismic loads, and so on.
Let’s talk about the artistic aspects, or the question is:
Q: What’s the best way to get the look, like in your catalog?
A: It’s a combination of working from several boxes, so that you get the best mix of colours and textures. It’s a process of laying the stones out in advance, to see what you have to work with. While installing the stones, you’re putting thick stones next to thin ones, smooth texture next to rough texture, and large stones next to small stones. Stand back frequently and look at your work. Are you getting the best blend of stones? If it’s a coarsable product, is it running level? Are you getting a good blend of all the colours? Are the corners blending well with the mixture of colours and flats?
Q: What are some of the differences between interior and exterior installations?
A: We’re often asked about the difference between an interior installation and an exterior installation. And there are a few things you can eliminate in an interior installation. For example, you don’t need to use 2 layers of WRB in an interior installation. However, we do recommend you still use 1 layer. The purpose of that layer is to keep moisture that’s in the mortar from being absorbed by the other building materials you are about to adhere to. You also don’t need to use a weep screed in an interior application. There’s no water to be drained. Likewise, the clearance requirements for an interior application are zero. You can go right to the floor. And that’s the differences in an interior installation.