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Robert Lamoureux: Plastic cement needs waterproofing

Your Home Improvements

Posted: February 25, 2012 1:55 a.m.
Updated: February 25, 2012 1:55 a.m.

 Hi Robert,
This is the second time I have written in with a question. Thank you for your first answer as you were right on the mark.

We went through a fairly large reconstruct and between sets of bricks, the contractor put in what looks like shiny concrete. 

That space between the bricks is about 1 1/2” wide and is above my bottom room that now has walls that are buckling and peeling since the last rain. I contacted my homeowners association and they are telling me it’s my problem because it’s an inside wall. Is this right?  Thank you as always,
Kate D.

Hi Kate,
The response from the HOA doesn’t sound right to me. The shiny cement you are referring to is plastic cement. 

If you have a cold joint between sets of bricks as you are describing and they did not waterproof underneath, then you have an issue.

If all they used was the cement in the joint without waterproofing, then it is not surprising you are having interior damage because the cement is porous. 

If you get enough sheeting, the water will find a way inside your home.

The only way to ascertain the cause of this leak would be to open up the drywall and perform a water test to the exterior. 
If there is no waterproofing, then it should start leaking within about 20 minutes. 

If so, I would suggest you document this through photographs and then bring this to the attention of the HOA. 

In this case, it would be the responsibility of the HOA as they are responsible for the envelope of the building, which is the exterior. 

You may have to do a little leg work on your own to get to the bottom of this.  When you open the walls, you may find that it’s a plumbing leak. 

I don’t know how your CC & Rs are written, but some HOAs are holding homeowners responsible for their own water and waste lines if they are exclusive common area use.

I have this brown material at the end of my driveway where it intersects the city sidewalk. I don’t know what it is. 

It’s fibrous, but not wood. Birds are picking at it and it’s starting to look bad. 

What can I do for this?  Can  it be replaced? Is this something I can buy and drive down between the driveway and sidewalk?  Thanks,
Don I.

Hi Don,
That is an expansion joint. It is put in during the concrete pour and is there to keep two pieces of concrete from fusing together.  

When it’s put in, it’s compressed by the weight of the concrete. A new piece would be too wide to get in there.

What I would recommend would be to first put in some backer rod and then a bead of Sikaflex about 3/4” deep. Because this is a urethane based product, it’s very forgiving and has a lot of elasticity in it.

This will allow it to bond well to both sides of the concrete. Make sure the concrete is clean before the application.

This should take care of the problem for a few years.

Hi Robert,
I have an apartment building that has a staircase with white concrete on the steps.

The steps are wooden, but there is a white concrete on top of that. That material is starting to fall apart in big chunks and I can see that some of the stairs have a little rotting under that. 

Do you know what this stuff is? How hard would it be to have this material replaced and repair the stairs? Thank you,
Michael C.

Hi Michael,
It probably goes up to a landing with a decking system with the same material called magnesite. 

It’s a product that is pretty much obsolete today and was primarily used between 30 and 50 years ago. 

There are some companies that still work with this material and make repairs. 

It’s a fairly durable product, but it is brittle like concrete — especially when tenants are moving in and out and you start bouncing refrigerators up and down the steps. 

If you’re seeing a little rot, the chances are there is much more that you’re not seeing based on the age of the building. 

I would recommend a complete tear off and replace all of the damaged treads and framing as necessary. Then apply modern waterproofing like a fiberglass decking system. 

This will give you a lot of longevity.  Be sure and put in a bullnose, a toe guard on the steps to help protect them from large appliances and furniture. 

Hi Robert,
I enjoy your column.

These last few rains have been a reminder to our HOA that we need to stay on top of our maintenance issues. We have upstairs decks, but there doesn’t appear to be any metal flashing. Our previous board had some decks redone and had the decking rolled over the stucco.  Now, from what I understand, the water is getting in behind the stucco. How can we prevent this from happening? Thank you, 
Abe M.

Hi Abe,
You’re going to have to break 10” - 12” of stucco.  If you’re building was constructed before 1978, you fall under the lead laws.  So make sure you have all of your painted surfaces tested for lead. 

May people are under the misconception that since they went through a rebuild due to the 1994 Northridge earthquake they are exempt, but this is untrue. 

Almost every day, someone will tell me that they had their building repainted, therefore they don’t need to go through the testing. 

The law states that if the building is pre-1978, the structure must be tested for lead.

Homeowners are not under the same constraints as contractors and are not mandated to follow the same laws when working with lead painted surfaces, however improper removal of lead can be dangerous. 

For your deck, you will have to install a wall to deck flashing. Break it open, repaper, put a wall to deck flashing metal. 

Keep it at least 2” off of the ground and then have the decking material roll up to the flashing material.  That way, you’re not covering the stucco. 

Whenever you roll the membrane over the stucco, any water that gets into the stucco is now encapsulated and will travel under the sill plate and inside the unit. 

We see this on daily basis.  It has to be torn out and completely redone. 

Many times when HOAs need to have work done, they look only at price.

There’s usually a reason why one contractor is much lower than another. This is why it’s important to work with licensed, reputable companies. 

Do it once, do it right.

We have designed a custom, full-color The Signal/Your Home Improvements T-shirt we will give you if we answer your question. The T-shirt is available to be picked up at our office.

Robert Lamoureux has 25 years experience as a general contractor, with separate licenses in electrical and plumbing contacting. He owns IMS Construction Inc. in Valencia. His opinions are his own, and not necessarily those of The Signal. Opinions expressed in this column are not meant to replace the recommendations of a qualified contractor, after that contractor has made a thorough visual inspection. Send your questions to


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