Is there a way I can fill cinderblocks in my basement to stop water from coming in?

Question

Could I drill holes in each block and fill with sprayfoam that would fill the blocks with a water tight seal and then paint the inside with drylock? How about hydroclay?

Answer 1

Filling the cavities in cinder block will not make the wall waterproof. The cinder block material at the block webs and the mortar joints will still be permeable and allow moisture through to the inside.

If you have serious problems with moisture ingress into your basement the proper fix is take care of a number of things:

1) For most sites the proper use of rain gutters to divert roof run off is used. Also the ground surface is graded to slope it away from the foundation so that water tends to run away from the basement wall area instead of down into the ground at the wall.

2) In some instances you may need to seal the outside of the basement wall with a suitable material that keeps water from even entering the cinder blocks at all. Proper sealant selection is probably the subject of another question so will not be discussed here.

3) In the worst case, particularly when the local water table is not very deep into the ground, it is necessary to dig down all along the outside of the basement wall to along the foundation which is below the basement floor level. Drain line with water entry holes or slots gets installed in a bed of porous material such as pebble rock. This drain line is sloped from one high point of the building perimeter around to a low point where it is then piped out to a drain field away from the building. The drain field allows the collected water to enter the soil over a larger area.

If you are going to the trouble of digging for plan 2 or 3 above it is generally advisable to do both at the same time. It is also a good time to consider the installation of below grade outside wall basement insulation material.

Answer 2

I live near a natural underground spring. It doesn't cause any problems when it's dry however when it would rain I'd have 6 inches of water in my basement, sometimes more if it was a heavy rain.

I sealed up the outside of the house and replaced the weeping tile as described above. This made a huge difference however I would still get some water after a heavy rain, just a few small puddles. This was devastating to me after all the work I had put in.

The fact of the matter was the 6 inch weeping tile I installed simply could not move the water away from the house fast enough.

I filled my concrete blocks from the inside with mortar using a funnel. Sika makes a liquid additive for mortar that makes the mortar very thin so it will fill in to very small cracks. It also makes the mortar waterproof.

I started by drilling 1/4 inch holes just above the basement floor to allow the water to drain out. Them I drilled a 3/4 inch hole about 3 feet up. I mixed the mortar a 5 gallon bucket at a time and poured it into the large hole. This caused more water to flow out of the small hole at the bottom. When the mortar started coming out of the small hole I patched it with hydraulic cement.

This is very time consuming but it works. I have yet to finish. Every spot that I treated in this fashion stays dry but I have a very large basement and there is an entire wall that needs to be treated.

I am going to try a self leveling polyurethane caulk. This is more expensive but I think it will be much faster and have the same effect. I am currently searching for a 5 gallon bucket of self leveling polyurethane and a pneumatic pump that will make it even faster. The pump for the mortar is very expensive.

The reason I had to go to such great lengths is because my basement is not constructed like the picture above. My basement floor is nearly a full course of block higher than the foundation. This leaves the block under the basement floor exposed to hydrostatic pressure. Basically even though the outside of the block is sealed it still fills up with water from underneath. There isn't much information on filling your blocks because that alone will most likely not stop the water.

Answer 3

The simple answer is no, it is impossible to waterproof a cinderblock wall by filling the cavity. Personally, I don't consider Drylock to be a permanent solution as it has a time-limited warranty and hydrostatic water pressure limits.

The most optimal solution is to keep water away, prevent it from ever coming in contact with your foundation - then Drylock is never needed. You didn't say how or where water is coming in. I suggest you spend a bit of time determining the ways how water is getting to a point that it is coming into your house, and then correcting that situation. If it is a case of grading - the land sloping towards your house, or downspouts dumping water near your foundation, then those can be corrected relatively easily. (Note that you should review the grading and downspout splashing yearly in order to avoid problems.) If you correct the drainage issues and are confident in them, then you could use the DryLock as a backup.

It is possible that perhaps your weeping tile (drainage at the foundation footings) is blocked - perhaps by tree roots or the weeping tile itself is missing or collapsed (the old style clay weeping tile did sometimes collapse). If you have access to your weeping tile (there is often an interior access to the weeping tile), then you may consider call a plumber who has a camera for pipe inspection to investigate that possibility. If the weeping tile is the problem, the water is most likely coming in at the join between the footings and the wall.

If it is not possible to prevent the water from coming to your property, then you probably have to proceed with waterproofing the outside of your foundation - this is a permanent solution but is more expensive and/or labour intensive (if you do it yourself). To do this:

1. Dig a trench down to the footings level all the way around your foundation - watch out for utility access (e.g. water, waste, electricity, natural gas) and other wires (e.g. wire going to a light post on your front yard). This needs to be wide enough to be able to work safely without risk of ground collapse (you will need a lot more space if your soil is very sandy) and also so you can work. The digging can be done by hand with a shovel (safest around utilities) or by a small backhoe if you have the space. You could probably hire someone to do this too.
2. Clean (pressure wash or stiff broom) and repair any foundation damage.
3. Apply waterproofing membrane - I would recommend something like the Blueskin membrane. Wrap it over the top of the footings, to help prevent water intrusion between the footing/wall joint.
4. Install rigid insulation such as the styrofoam pink foam boards. This will make your basement much warmer and more comfortable. This is an optional, as it has nothing to do with waterproofing, but it will make your basement much more useful.
5. Install the dimpled Platon membrane - this keeps an airgap right at the foundation, and allows any water to freely run down to the footings where it is carried away by the weeping tile.
6. Correct any problems with the weeping tile.
7. Backfill, ensuring the ground is sloping away from the house.
8. After 3 months, and at regular intervals (no less frequent than yearly), revisit the grading to ensure the ground is still sloping away from the house. You need to do this because the backfill will settle.

This sounds like a lot of work, but you CAN do this yourself. I had a friend who excavated his foundation by hand by himself one weekend, and then had his brother in-law help him with the other steps. Handling the rolls of material is definitely easier with two people.

From a safety perspective, once you get started you will want to get this done as quickly as you can so you don't have any issues with the excavation collapsing or people or animals falling into the excavation. Also, do this when dry weather is forecast as rain could lead to excavation collapse.

This image shows the waterproofing layers without the rigid insulation.