Basement Waterproofing:some Options for Dry Basements

When it comes to below ground waterproofing, there are normally three ways to get the job done:

- waterproof on a blind-side

- waterproof on the negative side

- waterproof on the positive side.

We will check all options in a concise way. More details you can find in other entries.

1) Below ground blind-side waterproofing.

Blind-side waterproofing is a method normally used in new constructions that are built on the property line. In these situations it is very difficult to excavate and work on the positive side. A type of blind-side waterproofing is also the waterproofing of slabs-on-grade.

One can use many materials (e.g. sprayed elastomers, PVC membranes, special SBS self adhesive membranes) but GCLs – geosynthetic clay liners – are the absolute kings for the occasion. The ability to harness the expanding capability of bentonite can do miracles.

Bentonite products have some distinct advantages:

- self healing properties

- simplicity in seam waterproofing

- are easier to work with on the rough substrates of many wall retaining structures.

Take care that the GCL should be confined in order to work properly.

All the above advantages certainly come to an appreciable financial cost.

2) Below ground negative-side waterproofing

This method should be reserved only when other treatments are not feasible.

Though, it has a great advantage: you don’t have to excavate and of course you always have full accessibility in case of failures.

On the other hand the structure is continuously immersed in water or water vapor and this is something that concrete and mainly reinforcements won’t appreciate  a lot.

Cementitious systems used for these applications are notorious for their tendency to crack (following substrate’s cracks).

Another parameter is that these products aren’t damproof and vapor migration could feed excessively the internal relative humidity causing severe condensation problems etc. Also it could induce delamination problems in many floor coverings.

But, my friend, most times it is difficult to dig!!!

3 ) Basement waterproofing on the positive-side.

This type of basement waterproofing is for new constructions. The big advantages of this type are:

1) the many options existing

2) the fact that concrete and reinforcements are well protected from water, moisture and chemicals and that’s a good thing for the construction.

But everywhere – particularly when you are kind of grumpy person – you can find disadvantages. When the basement waterproofing fails, you have to dig and cause a big mess.

Now, this is a tenable argument I think!

Let’s review in brief the main options for basement waterproofing on the positive side. More details you will find in other entries of this blog.

What we will finally choose depends greatly on two factors:

a) existing water or moisture

b) use of the protected basement.

3.1) Waterproofing with bituminous brushable products.

Please forget the simple bitumen emulsions based on oxidized bitumen. These are damproofing and not waterproofing products. Besides they gradually become rigid and crack.

Opt instead for rubberized asphalt products. A dry film of 1,5mm from these products can comfortably withstand medium hydrostatic pressures. Additionally these products have great bridging crack capabilities and remain flexible for many years. 

3.2) Cementitious brushable slurries.

As we have already mentioned these products being rigid have the tendency to crack. Some flexible two component products show a much better behaviour especially when reinforced with fiberglass meshes or non woven reinforcements.

On the other side cementitious products are easy to use and resist big hydrostatic pressures.

Some products  work with crystallization in depth and do a fine job by modifying the concrete structure.

Anyway I wouldn’t not opt for them, if I worked on the positive side.

3.3. Antiroot (type Jardin) SBS membranes

These are robust SBS membranes especially conceived for roof garden applications. Their mass is enriched with substances that deter root passage.

They are torched on a substrate carefully prepared and primed with the appropriate bituminous solvent primer .

The waterproofing layer is mechanically protected with a HDPE dimpled membrane.

3.4. Antiroot self adhesive SBS membranes

Antiroot self adhesive SBS membranes are easy to use peel and stick SBS membranes usually with 1,5Kg/m2 weight and 1,5mm thickness.

 Membrane is  placed to the sense of height with 10cm lateral overlaps. After having detached siliconized paper the membrane is pressed firmly on the substrate taking care to avoid air entrapment. Some special bituminous, elastomeric primer  is used for substrate preparation.

Mechanical protection of waterproofing layers is achieved with a layer of an appropriate HDPE dimpled membrane

3.5. Elastomeric coatings based on polyurethane, polyurea or combinations. They produce a tough, elastic, crack bridging, root resisting, seamless waterproofing membrane.

3.6. GCLs or Geosynthetic Clay Liners are a guaranteed solution in positive waterproofing. These liners possess unique characteristics as:

- self healing properties

- simple, no thrill seam waterproofing.

Can also be used for blind-side waterproofing.

Other options could be synthetic, one layer membranes like PVC etc.

Chris Strogilis

http://maconwaterproofing.blogspot.com