Polyurethane Injection involves injecting leaking basement cracks with a foam rubber seal. This type of repair to leaking basements is most appropriate on solid cast in cast in place concrete walls or slabs, such as underground parking garages or cold cellars and ceilings. It is not intended for block construction. This method of basement leak repair and waterproofing is the least expensive method provided your basement is unfinished and the affected area is easily accessible; no digging is required. Polyurethane Injection provides a permanent seal when properly injected into a crack by a professional waterproofing specialist like The Basement Waterproofing Guy.
How Polyurethane Injection Works
First, we drill holes into the wall about 4” deep on one side of the crack and on an angle so when the hole crosses through the crack it does so in the centre of the wall. For example, on an 8” thick wall we drill so the hole crosses 4” inside the wall. We drill approximately every 4” from one end of the crack to the other, and then we install nylon injection ports.
Next, we use a high-pressure pump to force in water and acid (this cleans and etches the crack) which we then flush with water and finally inject polyurethane. As the polyurethane mixes with the water 4” inside the wall it begins to expand into a foam rubber, the mixed product (foam polyurethane) begins oozing out of the crack and sealing it. The injections start at one end of the crack and continue every 4” to the other end. You see a continual bead of polyurethane rubber from one end of the crack to the other.
If the top of the crack is visible from outside you will see the rubber oozing out of it as well; the rubber seal goes right through the entire thickness of the wall unlike other solutions that only create a “V” groove and seal the first inch or two of the inside wall.
It is vital the polyurethane penetrates all the way through the wall to the outside to help defend against outside pressure (the ground can swell because of excessive moisture or frost). It is like breaking a pencil into two pieces, as you put pressure on one side of the pencil it creates a crack and weakness on the opposite side. This is the same for your foundation wall, as pressure increases from the outside, the inside wall can open up, but, because the polyurethane seals and protects against this pressure from the outside your basement stays dry.
By far this is the most economical solution, but be aware concrete
has a tenancy to shrink as it dries causing most cracks in foundations. Concrete
is a mixture of sand, stone, cement and water. Quite often water is added to the
mixture to help it flow through the forms easier. When this happens the concrete
sets and begins to harden, this process actually continues many years (concrete
continues to increase in compressive strength for years).
In most cases, the cracks remain the same size and once injected with Polyurethane can last forever. However, in some cases where excessive amounts of water was used in the original mixture the concrete continues to shrink and the cracks continue to open up causing the injected crack, as with a “V” method, to potentially re leak. Unfortunately there is no way of knowing how much water was originally used.
In our experience, the number of these cases is small. Most of the shrinkage occurs within the first 5 years, older homes have a smaller chance of shrinkage. The Basement Waterproofing Guy offers a 20-year Waterproofing-Guarantee on the Polyurethane Injection, so if the crack does open up within the Waterproofing-Guarantee period we will repair it no charge. Ask The Basement Waterproofing Guy about your specific situation and how we can help you stop a leaking basement.