I have a cinder block retaining wall along my driveway. It is about 2 1/2 feet high and covered with a thin coat of concrete. The concrete covering is falling off and I would like to resurface it.

How is it done? Thanks

 

Your best bet would probably be to use a lath wire (like tightly spaced chicken wire), and attach that to the existing wall using concrete anchors. You can then use any of a number of concrete mortars and/or stucco finishes applied to the wire lath to get the look you're after. Often, this is done in two coats - the first is a "scratch" coat, which is just to cover the metal lath. This coat is left rough - often by scratching the wet surface - thus the name. The roughness helps the finish coat adhere properly to the first.

I'm betting the reason your concrete is crumbling off the wall is that there is no wire lath in it now. The lath acts as reinforcement and holds the surfaceing together; much like re-bar in a concrete structure.

 

All the cinder block I have seen stuccoed was applied directly to the block. Unless the block work was poor 1 coat of mud was all that was required. Always holds up well especially when painted. There is a good chance that the stucco failed because of moisture seeping through from the other side of the retaining wall.

 

I also have a 40'L x 10'H cinder block wall that we are in the process of resurfacing. The stucco that was initially put on the walls 12 years ago cracked and/or fell off. I do have dirt right up against the back of the wall since it wasn't constructed correctly, so moisture does get through. We have installed drains and weep holes to help with that. In addition, about a year ago, we painted the wall with a Behr masonry paint when we removed the old stucco to improve the appearence.

I was told by another contractor that the new stucco will not adhere to that paint. My wall contractor was not going to wire the wall at all and I was arguing with him about that this morning.

My question is ... if we wire the wall without removing the paint, will the stucco hold? What type of wire and process is best for attaching the wire to the wall?

Any advice is greatly appreciated!!! Lori

 

Stucco should be applied to wire mesh, especially in the case of a retaining wall. The stucco mesh should be attached to the wall with masonry nails in the mortar joints.

The stucco should be a standard mixture and would consist of a scratch coat and one or two additional coats to the desired finish.

If you desire a color, the final stucco coat can be intergrally pigmented to a wide range of colors. Do not paint a retaining wall - you are just asking for trouble, no matter what a paint manufacturer says. A cement based coating product like Thoroseal could be used.

Dick

 

Thanks for the advice...
Unfortunately the paint is already on the cinder block wall. So, do we need to remove it before applying the wire? Or, will the wire work without removing the paint?

 

Because you are mechanically attching the wire and stucco to the block, the presence of the paint is not a factor. The paint can remain.

You said you have a 10' high wall. Is it a retaining wall for the full height? If the wall is sound with no structural cracks, it must have been designed and constructed quite well.

Dick

 

My wall contractor insisted that I don't need wire on these walls. Just so I can tell my wall contractor what I have been advised to do, how many years experiance do you have with walls like these?

For the most part, there are minimal cracks in the wall and nothing I would consider a "major crack". It does bow in slightly in the middle section. There were a few places at the base of the wall where the water from hard rains were shooting water through small cracks in the mortar. We added drains and rerouted the water away from the back of the wall to solve that issue. We don't believe the cinder blocks were filled with any concrete, there was no landscape fabric, gravel or sealant put behind the back of the wall. That is why I made the statement that it was not built correctly. I would not be surprised if it fails at some point.

Thanks for the advice, Lori

 

You asked about experience - 40+ years as a graduate engineer (civil/structural) - registered in 1966 (registration recently retired). Over 35 years in the concrete masonry industry working with designers and contractors. On code and standards committees. Involved with segmental reaining walls since 1985.

I have worked with general contractors, masonry contractors, lanscape contractors and concrete contractors in the U.S. and internationally. I don't know what a "wall contractor" is.

A bow in a wall is common if it did not have the stability to resist the loads. That is one of the reasons it is so difficult to design and build a long lasting, rigid concrete/concretemasonry wall. This is also one of the reasons that engineers try to use segemental walls instead of rigid walls if possible - they just perform better in tough conditions at a lower cost.

If you have a painted surface, I don't know how he proposes to get the stucco to bond to the wall for any amount of time. The presence of cracks indicate that water can come through and force off a stucco coat that is sticking to something (Behr paint) that does not want anything to stick to it. Only a mechanical tie like wire will hold it AND provide tensile strength to resist the surface cracking.

If you feel the wall will fail at some point, then it just a question whether the stucco will last long enough. One contractor says use wire mesh. The other contractor says is not needed. It is not a recommended process to apply stucco to a retaining wall without wire mesh. You can get away with a cement wash on an above grade wall in some climates, but not a retaining wall.

If your preferred contractor is so sure it will work, ask him for a guarantee and a bond. I think he would rather do it correctly.

Dick

 

Thanks..

"wall contractor" is simply my easy way to distinguish between my pool contractor and the contrator that is fixing this wall for us. He is a Masonry contrator with good references. I will pass on the advice.

 

Dick,

Thanks for the advice... My concrete masonry is going to wire the wall for us.

Part of the wall that we are stuccoing meets red clay dirt at the bottom. I know that in order to keep water out from behind walls on stucco houses that they cut off the bottom 4" or so and they seal the stucco with something. I assume we should do the same with this wall? What product should we used to seal the bottom at the dirt and at the concrete level too?

Lori

 

You do not need to put wire on a concrete wall. Wire is only used when you are trying to apply stucco to a wooded surface even then you would have tar paper under it.
If you are applying stucco to an existing concrete wall that is flaking I would do the following.
1. Knock off any loose pieces
2. put small ridges in the wall using a masonry blade ( this will help bond the new stucco.
3. You can also apply a concrete adhesive that will help bond the new layer to the old (Dont know how necessary this really is.
4. Apply new coat of mortor mix using a trowel