Expert: Dan Griffin - 10/30/2010

Question
QUESTION: Dear Sir;

I am putting up a knee wall with flagstone againt OBS covered with felt paper. They speak of a metal screen you put up after the felt paper to hold mortor and allow tieing wires to to secure stones. What is this screen called.

Thanks......Joel

ANSWER: jOEL, the material you are seeking is called lath.  You probably want stucco lath with spacers built in, which is usually called self furring.  Lath is available in metal with or without tar paper backing, ribbed, dimpled, galvanized, etc.  There are several brands of a fairly new material that is fiberglass which eliminates the possibilty of rusting the lath.  Make sure to use plenty of fasteners when you install the lath, the fasteners insure that the wall can carry the weight of the stucco.


Sure not a pick on you, but the sheathing you referenced is OSB - oriented strand board.

---------- FOLLOW-UP ----------

QUESTION: Dear Sir;

Well I attempted selecting flag stone (small, med and larger). Most stones 1.5- 2 inch thick. I viewed video and know of connecting thin wire to metal lath then securing stone with this wire ( for larger stone (10%) 12"x20" and a few larger.  My question is I have stones approx.(60% of total stone count) are 8"x8" (medium) and alot of 4"x6" smaller stone.

Do I have to secure smaller stones with wire?
Thanks.....Joel


Answer
jOEL,  there are two different ways to secure your stone.

One method would be to plaster the wall with a portland based product using lath as we first talked about.  YOu would then add a fresh layer of concrete mortar and imbed the stone work in the fresh mortar.  This method would not require wiring the stone work, but depends on the stone bonding to the plaster coat.  Here is a brief description of the process:
http://www.maconline.org/tech/materials/adheredveneer/adheredveneer.html

Another method would be much like laying bricks.  This method would not require the plaster and lath.  You use brick ties which are nailed to the sheathing and studs and lapped into the joints of the stone work as it is layed.  If you could go watch any brick being applied to a house it would be instantly obvious.  The stone work is usually held about an inch away from the tar paper to allow moisture  that enters the wall to fall to the bottom.  Here is a picture of an installation:http://www.flatgrassblog.com/2009/04/28/4230-raleigh-street-construction-update-

Here is a brief description of the process for stone work:
http://www.new-siding.com/brick-stone_siding-ratings-reviews.html

I hope this answers your questions.