I have been in the process— oh, for about THREE years now!! — of parging the foundation walls of my home. Most new homes since the 60s and 70s have concrete block or poured concrete foundations. But waaaay back in the olden days (as when my house was built), foundations were built from field stones or cut stones. My home has cut stones. Over the 150 year span that my home has been standing, the field stones are still in excellent condition– it’s just the mortar that stinks.
Stone foundations have limestone mortar. It is water-permeable and over time and rodent-chewing (chipmunks are notorious for chewing away the mortar to build nests between the stones), the mortar begins to fail. In severe cases, this can cause foundation failure. In less severe cases (such as mine) this can mean a pocked, ugly appearance and some water leakage. Parging is the application of a thin coat of sticky cement over the wall surface. I’ve got about half of my interior basement done– what a job! My basement is huge and has 6′ high walls– and about 1/3 of the house’s exterior foundation wall (about 2 feet high).
The mix you use for parging must be special– it has to be sticky (that is, it must stick to a vertical surface without plopping down and off) and must remain stuck to the walls after it is dry. I had one dummy at Lowe’s tell me I needed mortar mix for the job, and me- being the dumb homeowner– listened to him and bought $200 worth of the stuff. Only to find that this is the WRONG stuff and crumbles off over time. :-p What you need to use is something call Sand Mix. It’s a combination of sand and portland cement. It should not crumble off if applied properly. There are even some acrylic additives you can add to the mix to make it even stickier- the additive is a lot like Elmer’s glue and comes in tall bottles. You pour it in to your Sand Mix mix. I didn’t use it. I’m too cheap (the additive is very pricey). I mixed up the Sand Mix and so far, it’s been working well. This is what I did about four years ago, and it’s holding up great:
To make the mix, you add water to the Sand Mix. You should only mix up as much Sand Mix as you are going to use in about 30 minutes. Otherwise, it will start to harden and won’t work anymore. Here’s what you will need for parging your walls:
- Sand Mix
- a bucket
- water (hose or watering can)
- spray bottle filled with water
- cement trowel
- cardboard or kneeling pad for your aching knees
Before spreading on the stuff, make sure your wall is free from crud, like spiders’ webs, frass, and loose mortar. You will also want to dig down in the dirt a little, so that your parging line will not be seen should the soil shift around your foundation. I usually dig down about 3 to 6″, depending on the soil and the wall itself. Some folks go much deeper down.
Now, get your spray bottle and moisten the wall. This helps the parging mix to stick onto the wall. Don’t saturate your wall with loads of water– just get it wet.
Now lay your parging mix with your trowel, in 1/4″ to 1/2″ thickness.
Corners and around windows are the hardest, so take your time. Parging isn’t a difficult job, it’s just tedious. While parging, I found a few areas where moles and/or chipmunks had chipped mortar away. Grrr. I filled these holes in, to keep them out. Parging helps keep out water, too.
Click to enlarge any photo.
I am not too fussy about how smooth my mix goes on. Just laying on the mix is a 100% improvement!
Allow to dry for 36 hours before moving the soil back into your trench. The parging mix will change color as it dries, to a light gray. You can leave it this color, or paint it with some waterlocking paint, or exterior concrete paint. This job is so easy that you can even have the kids do it. You just have to make sure that they are consistent with the thickness and apply it so that everything is covered completely.