A Lot Of Stucco Cracks.

kgphoto

Hey all,

I just stucco's a small 50: inch x 96 inch section of wall. It has cracked like crazy. ( get it - "crazed?")

Construction details: 1/2 Plywood, gapped properly, "K-Lath" with two layers of paper, 1 1 /4" staples after first tacking it with 6d nails. Diamond lath around the stub outs and in the corners. Three coat, but only two applied so far. Several days between coats, so not a rush job. Scratch coat sprayed with water before adding brown coat. Fairly heavy brown coat. Colton Plastic cement and sand mixed 1.5 : 3. Mixed in a cement mixed, throughly.

The only thing I can point to is that it was the week we had very hot days and it gets direct morning sun. I misted it a few times.

Normally I use LaHabra Stucco base coat in the bags, but this time I thought I would try the bulk method.

So do I tear off and re-do? Can I expect my color coat to fill in this amount of cracking or will they continue to telegraph? Should I dry-pack powder in the cracks or mix up some more base and push fill them?

Any thoughts?

I will attach pictures in another post.

thom

Generally, cure (soak the stucco thoroughly, deeply, every day for 6 days after scratch, then again for six days after brown. When dry, the stucco won't cure, it needs to be wet.

Probably the finish will be fine. Lots of fine cracks are pretty normal for the scratch and brown.

I've switched to a synthetic finish coat because 1) fewer cracks, 2) less problems with staining, 3) does a better job of preventing water intrusion, 4) consistent color.

Years ago I switched to the one base coat system. Fiberglass fibers in the base coat. I was hesitant for a few years but the system works fine. It's been in use around here for about 25 years and is holding up fine.

Tscarborough

I googlized that brand of "plastic cement", and left a voice mail for the technical service guy at Colton to find out exactly what is in "plastic cement". Without knowing that, and taking a wild stab at crazed stucco, it sounds like your mix is too rich/strong. That is, 1.5:3 is stout, much stouter than it needs to be. Stucco does not have to be compressively strong, it has to not shrink and have as much flexural strength as possible. When the tech guy calls me back and I find out what their grind is for "plastic cement", I will post the result.

kgphoto

Thank you both for your replies. I look forward to hearing what the Colton specialist will tell us.

y0manda

16-18 shovels of washed sand to a 94lb bag of plastic cement. The reason you are having cracks is because there is not enough aggregate in the mix way too rich.

tkle

Colton is the only brand I'll use.Good product.
Sounds like the mix is too rich.Being that rich it was also possibly applied too thin.Depending on how bad it is you might consider another brown coat.Your color coat won't fix much.

kgphoto

Never could figure out how to measure accurately with a shovel, so I fill a 1 gallon bucket with sand, tap, scrap and dump, three times. Then one of the Plastic Cement. It didn't flow or feel right so I added a little more Plastic to get to the 1.5 buckets of plastic to 3 buckets of sand. Mixed in a mixer (typo above). Add water a little at a time until I got to spreadable consistency.

I think I will just go to bagged material for the rest of the wall and play with this later on a test wall to see if I can find the reason why.

Someone else gave me a suggestion of 3 sand, plus 1 plastic and 1 portland.

Thoughts on that recipe?

tkle

Stick with the Colton plastic.Use 1/2.5 c/s ratio with fiber.Wet before applying second coat but no need to keep wet.