Stucco Project

When they tore the roof off, they had to tear into the stucco on the sides of the dormers to put in the copper flashing.  It soon became evident that I needed the mason (Chuck Hipp) to stucco the sides of the dormers before the roofing tiles were installed.

This is an important project because it involves many decisions with respect to the historic finish and the modern finish.  Originally, the house was constructed with “L” shaped solid concrete block, set in mortar in opposing inside and outside running bond, with stucco on the exterior and plaster on the inside.  The total exterior wall width is close to 12 inches!  No insulation.  This is a very unusual construction method and I have not been able to find any reference to it in a quick web search.  These are not cinder block but are solid and very heavy!  The construction method yields a very strong wall by virtue of the laminate created with the internal block and mortar and the inside and outside skins of plaster and stucco.

Back to the stucco.  The finish on the outside of the house was a thing of beauty when first constructed.  All of the accent elements such as the concrete window sills and the porch rail caps, ect. were colored a rusty red.  The finish layer of stucco was a very light pink.  In addition, a DASH finish was added.  This involves laying the final coat of stucco and, while wet, flicking and aggregate (small gravel) over the surface.  The gravel was then pressed lightly into the wet stucco with a trowel to half embed the gravel in the surface.  this leaves a very tight layer of exposed gravel on the surface.  What makes this even more unique, is that the gravel used was a very carefully selected mix of very fine (1/8″ or less) grey granite, sea washed milky and clear quartz and dark red stone chips (composition unknown).  All I can say is that when the sun struck the side of the building, it must have sparkled like jewels.  I have seen this effect on small sections I have cleaned.

Here are the problems.  Cleaning the existing finish is impossible.  Over the last century, the house has received several coats of paint over numerous poorly done patches and repairs.  One of the paint coats is particularly tenacious, a battle ship grey.  It is speculation but I suspect that  the house was painted grey sometime after WW II with surplus ship paint.  A 3800 PSI power washer cannot touch this stuff.  Chemicals might get most of it, but that wouldn’t solve the problems of the poor repairs.  Age is a problem as well.  I estimate that approximately a third of the gravel has been loosened such that any efforts to clean the walls results in large patches of gravel being removed.  Duplicating the the finish is not impossible but it is very difficult and expensive.  Coming up with the matching mix of aggregate is very difficult and expensive.  Finding masons with the skill to do the application is very hard and finally, just the labor involved is very expensive.

After considering all of the above and several experiments, I have settled on the following course of action.  First the exterior is pressure washed at 3800 PSI.  This knocks off all of the loose gravel, all of the white paint and some of the grey paint.  This leaves a very rough and sound surface to grab the new stucco.  This also exposes loose and cracked elements of the walls that require repair.  Next the repairs are made and covered with high strength portland mortar.  Any exposed exterior wood lath is replaced with concrete board or hard backer board and covered with a scratch coat of stucco.  Finally, the exterior is covered in SBC stucco.  This product, know as quickwall from Quickcrete, is widely used in drywall construction.  It consists of a cement based stucco ammended with acrylic bonders and includes fiberglass fibers for reinforcement.  This stuff is awesome.  It is white, bonds very well to my prepared surface, and is very strong.  It is usually applied in 1/8 thickness in drywall applications.  In my case, it ends up almost a quarter inch thick because of the exposed aggregate.  A first coat is applied very tight to the gravel and a second, thin finish coat finishes it off.  It is very lightly troweled to leave a slightly textured finish.  Heavy troweling results in a very smooth, slick finish that is less interesting to the eye.  At least my eye :).

The dormers had to be done as soon as possible in order to allow the roofing to proceed.  They provided the test case for the whole process so we started with the back of the house in case we really screwed it up!  We immediatly discovered that the existing stucco on the sides of the dormer was applied over board sheathing with no wood or metal lath except for a few repairs.  It was much easier to just remove all of the old stucco.  This left almost an inch of depth to build back to the finish level of the block on the face of the dormer.  We first put water and ice shield over the sheathing and then screwed on concrete board  to bring the surface to the proper thickness.  This provided a very smooth surface to bond the SBC.

The face of the back dormer was not pressure washed because my intention was to only stucco the dormers and delay the rest of the house until building the garage.  I soon realized that I might as well proceed with the entire house.

The face of the front dormer was the first large scale pressure washing that I attempted.  It was easy because I could stand on the porch roof.  Easy as in not having to set up scaffolding to get it done.  It is not that easy to hold on to a pressure wand blasting gravel off the wall into your face at 3800 PSI.  The gun has a kick!

On weekends I try to do some work myself.  I went out an purchased an extendable wand for the pressure washer and attacked the Bump out on the north side.  I will be building an extension on this bump out of about seven feet.  This area will be used to add His and Her’s walk-in closets for the master bedroom.  I plan to build this addition at the same time as the detached garage in the back.  Anyway, the window will be turned into a door and the exterior stucco on the outside of the bump out will become an interior wall.  This I intend to cover with plaster in keeping with the rest of the interior.  I figured that it was better to pressure wash the wall prior to building the addition to prepare for this.  If you think the pressure washer 3 foot wand has a kick, try it with a 12 foot long extension wand!

I determined that the stuccoing process could continue without disturbing the work of the carpenters or roofer overmuch.  The next step was to start work on the south side of the house.  There is a dog run on the entire length of this wall.  My mason and I realized that the basement windows needed to be blocked up and fitted with storm vents.  I live in a flood zone next to the chesapeake bay.  We discovered that the bonded beam above one of the windows was badly cracked and had exposed rebar.  They removed the badly cracked concrete and the rebar.  The windows were filled up with block and room was left for two storm vents in each window.  The block provides the support for the bonded beam that was damaged.  Surprisingly, the rebar was not  badly rusted and the cut end shows the soundness of the steal in the house.

The dog run is about 5 feet wide from the wall of the house to the neighbor’s fence. Regular scaffolding will not fit here.  My mason rented special 4 foot wide scaffolding which was the perfect fit.  The weekend after the scaffolding arrived, I decided to set up and start pressure washing the south side.  It took longer to set up the scaffolding and tarps to shield the neighbor’s side yard than it took to pressure wash 6 feet high and the 50 foot length of the dog run.  After that the mason’s crew took over and finished the pressure wash in a day. Then they started on the stucco with the SBC.  That stuff really looks nice!

The pressure washing revealed that there was damage above the dinning room window.  I was concerned because, again, there was rebar exposed when the weak concrete was removed.  This time there could not be block to improve the support so another solution was required.  My mason was sure that a strong portland mix would hold it as long as we put a coating of silicone on the rebar.  This was to prevent pressure on the concrete patch from any future rust on the rebar.  I felt that there was no danger of the beam above the window giving way but I was concerned that the portland would not provide strength in adhesion to the concrete on the leading edge of the window.  So, we coated the rebar with rust reformer.  This stuff stops rust by chemically combining with the rust.  We added a thin coat of  silicone calk for pressure relief.  Then we filled the crack half way with 5000 psi epoxy.  The rest is filled with portland before covering with the new stucco.  I hope this will provide additional strength for the lower part of the window edge.  Only time will tell.  I am not worried about the structure since I know that the load bearing beam above the window is contained in a box above the window proper.  I do hope to save the overhang from further deterioration.