STUCCO NEWS.NET

Mr Bullard-

I worked with you a number of years ago when I was a designer at a Washington DC design-build firm. I thought that you did a really great job on the projects that you were involved in and I appreciated your expertise.

I have since moved to Dallas, TX and started my own architectural practice.

I am currently working on a project and was hoping to mine your expertise again. I've heard other architects discuss using a hybrid stucco system that I can't seem to find much in the way of information on. The system is standard 3-coat portland cement plaster over metal lath over (2) layers Grade D paper over EPS insulation over OSB wall sheathing and 2X6 studs at 16" OC. I really like the idea of having the EPS insulation on the outside of the framing and I also like the idea of the standard 3-coat cement plaster. Is this something that you have done before? Do you have any thoughts on this or do you have a good resource where I might go to find the specifics on this exact system?

Thanks,

Garth

Garth M Russo, AIA
Live Oak Architecture
www.liveoakarchitecture.com

Z furring is an excellent method of stucco over foam board. It can be used for furring over block, concrete, wood sheathing, or what have you. This eliminates the need for hanging the lath on nails, and embedding the lath in the foam, causing failure by not allowing the mortar to key behind the lath.

A view of the z furring.

The center is only the thickness of the sheet metal allowing for a minimum of heat loss, as opposed to furring with furring strips, etc.

I bought this Z furring in 10 foot lengths. This is 1- 1/2" furring for 1-1/2" foam.

I got the foam board in 4 x 8 sheets from a drywall supply. This is score board. The sheets are pre-scored for score and snap for both 24" and 16" on center. 24" O.C. may be fine for drywall, but I really needed 16" for stucco. Foam that isn't scored can be ripped with a circular saw.

The procedure is nail on a furring channel, slide a foam board behind it, nail, slide, nail slide. Pink panther indicates that this is made by Dow chemical company, another large corporate polluter, but probably not nearly as bad as Dupont.

We nailed the furring up to the old painted block using stub nails and a magnet. It can also be shot to block, concrete, wood, and even steel.

The channels provided a very good, positive screw attachment for our self-furring metal lath.

As a warning, this used a lot more mortar than we usually use for a scratch coat. The foam is soft, and a lot of mortar squished behind the lath. This extra mortar does make for a better, more solid product.

Please check out this link to a building we did in Front Royal, Virginia.

Old stucco and lath was stripped down to the diagonal sheathing. We put on One by fours for furring strips as additional reinforcement for the Z-furring. This Z furring is 2-1/2" so we wanted a solid reinforcement. If you ever do this, remember to allow an extra 3/4 inch for the furring.

Furring was covered with a layer of 15 weight tar paper and a layer of rain screen.

2-1/2 inch Z-furring is put on with 2-1/2" insulation board. Foil faced polyisocyanurate insulation has an incredible R-factor of 16.

Foil faced polyisocyanurate board is cut to fit.

Z-furring follows the wood furring under the rain screen.

Metal lath is attached to the z-furring using wafer head screws.

Scratching mortar on metal lath.

Pebble dash stucco matches original 1908 building exactly. Portland cement is far more durable than the original lime and sand, and a R-factor of 16 beats zero.