I’m going to install faux stone around my gas fireplace. I talked to the manufacturer and they said it can be installed over wonder board ,if you put a scratch coat(fortified with latex additive) over the wonder board first.
Has anyone else done this before? Can you skip the scratch coat and put the additive into the mortar used to set the stone?
Replies
All you need is regular thinset to hold the tiles to the wonderbd. I have done many fireplaces,hearths and tiled walls for coal stoves this way.
I won't be setting tile , its a fake stone like what you would usually see on the exterior of houses
Tiles ,fake rocks its all the same to the thinset.
Having done a few of these, I generally go with what ever the installation destructions that come with the cultured stone say.
That's generally had a scratchcoat first, which seems to be what evens the lath applied over the substrate out, the lathe providing a mechanical fasteneing to the structure.
I've seen cultured stone just thinset (but that was backbuttered on a pretty big notch, too) straight onto durock--but those were always very small, interior-only applications, too.
For anything more than a sheet wide and/or tall, the scratch coat seems (to me, at least) to make a nice, uniform, plane surface to work on, no subtle changes at sheet joints or the like that might (just might) "telegraph" though the finished cultured stone.
Now, all of mine were for customers, or sub-ed out for customers--so, going "by the book" was as much for business reasons as anything else. For "just me," I'd likely have the brown coat on out od habit as much as anything else. That, and it would be the "mud job" on the board, too.
ad73,
First off, don't use thinset - its not meant for cultured stone, it meant for tile, slate, etc. Use type N morter, which is dry-mixed in the sack and you add the water. It is meant for grouting stone. The yard where you get the stone should have it. See: http://www.masoncontractors.org/newsandevents/masonryheadlines/5282004815.php
Typically, you install the stone over metal lath, then apply a scratch coat on it. The wonder board is like a scratch already, so I don't understand why you would need it. The morter shoud adhere just fine, since the wonder board is concrete. I would make sure to use concrete, not fiber board. That being said, I would just nail up lath to the wood structure and spread a scratch coat. I attached a picture of an example.
If you do use it, I would definately thinset / mastic the wonderboard to the structure underneith to ensure a solid base.
Good Luck.
I don't know much about (beyond subbing it out) this but would like to learn. Generally I don't like fake stuff but I love the look cultured stone... most people can't tell it's fake... And at maybe $13 a sq ft installed vs $20 for the real thing, it's definately worth consdiering. anyway, you said:
>> Typically, you install the stone over metal lath, then apply a scratch coat on it. <<
I guess you mean nail up the lathe, apply scratch coat, then install stone?? Also, I thought the scratch coat was supposed to have some texture to help the stone's mortar to stick?
Yes - you nail the lath up to the wood frame with u-nails.
I don't actually scratch the mud on the lath - not needed. Basically, plaster about 15 sq ft let it dry at least 30 min, and then start laying the stone on it. I start at the ceiling and work my way down, since it keeps the stone the cleanest. Plaster the section ahead - time you lay the stone, grout it (use a grout bag), strike and brush it, the section will be set up fine.
If you not done this before, make sure and start with a pretty small section. You dont want it to get away from you (dry too fast). If you are doing the dry-stack look, it isnt quite as much of an issue.
I wondered about the top down thing... form the pic... Wonder why bricklayers don't do that? If there is one thing I hate it's 'painted up' brick.
Merry Christmas
Edited 12/24/2005 8:33 pm ET by Matt
You can't lay brick from the top down, becasue brick requires the supporting structure for the weight. The same it true for real stone. Since the cultured stone is light weight, you can get away with it. To keep it clean you need to brush it often - the best masonry jobs are those that get struck well and brushed a lot.
Merry Christmas!
Gottach-ya!!! The brick/top down thing was a joke! Guess I shouldn't have left off the smiley face :-)
Got it! You never know...
On more thing about the stone and doing it from the top down - you should pick out about 10 really pretty stones and place them on the faireplace where they will look nice, and lay the rest in around them. It helps maintain balance in the layout.