Replies

1. 
   Dave45 | Apr 29, 2005 04:48pm | #1

   I've done several window replacements over the past few years and have found that stucco patch gives me the best results.  I don't have the brand name handy, but it comes in 10# bags and apparently has latex in it.

   After I get the window flashing and wire in place, I put on a first coat and hold it back slightly below the final thickness.  I leave it pretty rough so my finish coat will have good 'grab', then wait at least 24 hours before doing the finish coat.  The finish coat is where I bring it out to final thickness and ....here comes the tricky part.... match the existing texture.  The patch material I use is white and it's sometimes difficult to ignore a color difference but still get a texture match.  Some of my earlier repairs (on my own house) are somewhat noticable, but the later patches are invisible after the house has been painted.

   One other thing I strongly recommend is that you don't even try to work to a straight edge in the old stucco.  A lot of people use a masonary blade and cut the stucco away from an old window.  If you leave the straight line, your patch will eventally show through.  I always break out the old stucco with an air chisel and leave a jagged edge.

1. 
   cb900 | May 03, 2005 03:48pm | #3

   Good tip about the jagged edge. I will use that. Thanks for the info.

   Cam

2. 
   ClayBabcock | Apr 29, 2005 06:49pm | #2

   I am definitely no expert, having only two window replacements under my belt, but I did really find that the more expensive water resistant stucco was much easier to apply because it contained a lot of plastic fibers. As with concrete, you don't want your stucco to completely dry for four days to allow for maximum strength. As far as set-up time between coats, I, myself don't actually KNOW. But here is the content I just found on a site called diydata.com (it appears to be a british site). Sure wish that I'd read this first:

   Stucco Techniques

   Stucco has traditionally been applied in 2 or 3 layers. The first layer is normally about 10mm (3/8 inch) thick and is referred to as a "scratch" layer because once it has been applied, the surface is 'scratched' to provide a key for the second layer.

   The second layer (if used) is another "scratch" layer about 10mm (3/8 inch); this is sometimes referred to as a "floating" or "brown" layer.

   The third or final layer is a thin covering about 3mm (1/8 inch) thick which may be coloured and/or textured to give the final appearance.

   For the first layer on masonry, ensure that the surface is free of loose partials and, if necessary, roughen the surface to provide a good key - rack or chisel out the mortar between bricks/blocks.

   Dampen the masonry or laths before applying any mortar, this will help prevent them from pulling moisture out of the mortar too rapidly, which could cause cracking, loss of bond, and generally poor quality stucco work.

   Place some mix on a builders hawk, push some mortar onto the area using a steel plasterers float and spread it over the area. Make sure that it is worked into the joints of a masonry subsurface or in between/behind laths or into the wire mesh. Keep working within a limited area (say 1 metre/yard square) to achieve a thickness of about 10mm (3/8 inch), and then move onto an adjacent area.

   Allow the mortar to slightly harden (2 hours or so) and criss-cross score it as shown to a depth of about 3 mm (1/8 inch). Alternatively (if stucco is being applied to a large area) make up a 'rake' by driving a number of nails through a length of 50 x 50 timber at 25mm spacings - make sure that all the nails project the same amount from the timber.

   Allow the first layer to harden for 24 to 36 hours. Do not let the layer dry out, if necessary, keep it damp by misting it with water, do not spray it with a pressure hose as this will dislodge the mortar.

   Apply and score the second scratch layer in the same manner as the first layer.

   With a flat finishing trowel, apply the final layer to about 3mm (1/8 inch) thick.

   If desired, apply a texture to the final layer after it has hardened for 2 hours or so. A wide choice of finish textures can be used, the only limitation is the imagination of the worker. When choosing a texture, make sure that the pattern can be repeated across the full area. The following indicates how some popular finishes can be achieved:

   Smooth finish. Smooth the final layer several times using a steel float as the mortar begins to go off, occasional plunging the float into water will keep it clean and prevent it pulling mortar away from the wall.
   Swirl texture. Use a float in an arcing motion on the mortar just once while it is still fairly damp, and then leave it to harden - a wooden float often gives better swirls than a steel float.
   Stippled texture, After the mortar has started to dry, hold a stiff broom at an angle to the wall and pat the bristles onto the surface to give the desired pattern.
   Wavy, scratched texture. Smooth the final layer, allow it to dry slightly, then lightly draw a brush across the surface using a path to give the desired effect. Keep the bristles free from mortar build-up by knocking the brush head after each pass across the surface. The stiffer the brush, the coarser the pattern.
   Imprint finish. Smooth the final layer and use whatever necessary to make the desired imprint(s) (e.g. leaves, shoes, hands, the paws of pets or whatever). If required, leave the surface to further dry and lightly use a float or brush to soften the edges of the imprints.
   After the stucco has been completed, keep the mortar damp over several days; lightly mist the surface occasionally if necessary.

   Complete the job by sealing around doors and windows frames, these are areas especially susceptible to the ingress of water.

   Leave the mortar to dry out for at least six weeks before applying cement paint or colour wash if required.

   General Tips for applying Stucco

   To apply stucco, the skills of a plasterer are necessary. The following guidelines are important to remember:

   Only mix enough mortar as can be used within about one and a half hours. The actual time will depend upon the weather (the mix will dry out quicker in hot or dry conditions); experience will be the best guide. Any remaining mortar should be discarded; it should not be remixed.
   If coloured Stucco is required, add cement colouring dye to the mix for the final layer. Carefully note the measure used so that identical proportions can be achieved with each separate mix of mortar.
   Stucco mortar should not be over mixed - hand mix for 10-15 minutes after adding the water. Over mixing can cause the mortar to set too quickly, this may cause cracks and poor bonding to the underlying surface.
   Wooden laths and masonry subsurfaces should be thoroughly damped before applying the mortar - this will prevent the subsurface drawing moisture out of the mortar. Bonding agents (such as a weak PVA adhesive solution) will also aid bonding to existing masonry.
   To avoid cracking, it is imperative that mortar is not allowed to dry out too quickly. Avoid applying Stucco in direct midsummer sunshine or very hot/dry conditions. In hot weather, keep the mortar damp for 48 to 72 hours after application.
   Stucco should not be applied in cold weather (below 5° Celsius/40° Fahrenheit), or if there is danger of frost during the 'drying' period.
   Cover the ground at the foot of the wall so that any dropped mortar can be easily removed. Lay down some old planks or a tarpaulin, alternatively spread some sand to keep the mortar off of the ground.

1. 
   cb900 | May 03, 2005 03:49pm | #4

   Thanks for the info. This is exactly what I was looking for.

   Cam

1. 
   ClayBabcock | May 03, 2005 06:31pm | #5

   Glad I could help. Like I said earlier, I wish that I'd found the site before I'd done my own scratch coats (one of which isn't, well, up to scratch).
   best of luck