Handyman project: mortaring bricks to seal out rain

A project to prevent rainwater from seeping through bricks into the basement



Heavy rains have resulted in several inches of water accumulating in the basement. This is a handyman project using mortar and rocks to lessen seepage. It’s a step-by-step guide, not difficult. This is a public domain document; feel free to copy it without attribution (including pictures which are public domain). Comments? Write below; I’ll try to respond. Like this? Add weblinks. — tom sulcer March 2011

Light rains are not a problem, but a heavy downpour brings several inches of water to the basement. It’s not fun sponging this away. There is no sump-pump. Ideally the exterior around the foundation of the house is sloped to keep water away from the foundation, but this isn’t always possible. Sometimes, what I’ve found, is it is necessary to go around the foundation, add mortar where water may be getting in, and see what happens.

Note: This is a beginner to intermediate handyman project.

Here’s the exterior of the house. My hunch is water hits the raised driveway, then collects in a low area between the basement stairwell (under the two doors) and the driveway, then seeps into the stairwell or foundation from this point. So my aim is to seal possible entryways and raise this area a few inches or so.

Here’s inside the stairwell, looking down. There is evidence of moisture.

This is the low area between the stairwell (left) and the driveway (right).  I scrape narrow areas with a screwdriver and dug with a small shovel.

I find matching slate rocks from the backyard as well as rocks of varying sizes. Mortar will act as a glue to hold them together. As a general rule, mortar is strongest in small areas, such as a half inch or so; try to avoid having a thick section of mortar, since it might not hold. An alternative would be to use only concrete. But I like mortar since I can use it between bricks and in-between cracks, as well as the underlayment for large flat stones or slabs.

Tools needed include: 5-gallon buckets (or else a mixing trough for the mortar); trowel; water supply (I use a hose running slowly); mortar (the bags are often heavy — I used two bags of 70 pounds each); rubber gloves (to protect hands — do not expose skin to mortar or concrete). Sometimes I pile tools in a bucket to make it easier to carry. Get everything ready before you mix the mortar. Get clean rocks nearby (wash them with water, rub them). Have a spare bucket with water in it to put tools so mortar won’t harden on them. Put down a tarp if there’s a possibility of mortar getting on a surface. One handyman tip: before putting on rubber gloves, put something slippery on your hands, such as hand lotion (even dish detergent will work); the idea is to make it easier to remove the gloves when you’re finished. Generally you should have a rinse-area prepared ahead of time, such as another bucket filled with water; so you can stash a tool in it to keep the mortar from hardening. Having a garbage can ready can also help speed the clean-up later. Another handyman tip: mixing mortar by hand takes strength, so alternate your hands to keep your muscles from tiring too quickly. And use a power-mixer or drill-driver if possible. (Large projects: consider renting a mixer; ask store people how to use it.)

Prepare the mortar. A drill with a mixing blade can be helpful to stir mortar inside a 5-gallon bucket. Mortar is a dry powder. The technique I use is to add about a fifth of the bucket of clean water first, then add in mortar in small amounts, stirring as I go. It’s tough work. I use the drill-mixer to help. When the mixture gets soupy, it’s almost ready — keep stirring, and keep adding small amounts of mortar. Finally, when the mortar gets semi-thick so that the trowel stands up in it, it’s ready. If there’s TOO much mortar mix, it will feel clumpy; if this happens, add a small bit of water, and keep stirring, and try to get the consistency right. This is why it’s a good idea not to fill up the bucket with too much water or mortar at the beginning (you have room to add either water or mortar as you go). What you want is mortar which has a firmness and consistency, and feels heavy, and will stay on your trowel. In the photo, the trowel is standing up — the mortar is ready.

Comment: Remember cement mixers on the highway are always turning, and this is for a reason. Mortar, like concrete, will harden if it sits still. So when the mortar is ready, apply it fairly soon thereafter; mix it from time to time if possible. Don’t go to lunch somewhere and return hoping to apply it. If it sits for an hour or so without being mixed, it may become unusable. This goes for tools with mortar on them, as well as containers such as mixing troughs or buckets. Mix it; apply it; then rinse your tools and containers if that’s your last project for the day.

With the trowel, I add the mortar mix in the holes. I use the trowel to squeeze mortar into the tight cracks. Then I add rocks — whichever ones fit. Rocks + mortar mix = strong combination. Try to push the mortar in tight to get air bubbles out. The mortar mix is wedged between the brick foundation (near top) and against the steel door siding (left). I add slate slab rocks on top of the mortar. But it’s still not high enough. I need bigger slabs.

This slab I name “Iowa”. I end up not using it.

This one is “Illinois”; it’s on the tarp. It fits better so I add it. It must set on top of mortar, and have mortar around it, to make sure it stays in place.

I add Illinois to the area. And more rocks. The area starts to get higher near the foundation, hopefully channeling future rainwater away from the foundation. The point (lower middle to the left) is the bottom of the “Illinois” slab. The mortar mix needs smoothing. But I will add more slabs, stones and mortar.

I add rocks and mortar mix to the crack where the steel door meets the foundation. This is the exterior of the house, so beauty is not as important as keeping the water out. Later, I smooth the mortar mix, sloping it away from the foundation.

On the other side of the steel door, there is only a tiny crack. I add mortar mix (with small stones and rocks interspersed), pushing the mortar mix into the crack between the backyard and the foundation, and pushing in stones too, and smoothing it over. I slope it away from the foundation of course.

Last, I add plastic covering over the mortar mix, with rocks to hold down the plastic. This helps it cure more slowly, making it stronger, and less likely to chip or crack. Hopefully it won’t rain in the next day or so. After a few days, I’ll remove the plastic.

What’s important is to rinse buckets and tools, such as the trowel, soon after finishing, otherwise the mortar will harden on them and make it very difficult to re-use.

The real test is when there’s the next big rain; most likely, there will still be some seepage, but hopefully it won’t be as much as before. There’s more caulking with silicone to do in other areas  (but that’s another project.) What’s next? Wash hands, take a hot shower, and have supper!

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