Parking Structure Traffic Topping/Waterproofing

[ajk1]

We normally provide a hot-applied waterproofing membrane overlaid by 2" to 3" of asphalt wearing course, as the waterproofing system on parking garage roof parking levels (CSA Standard S413 requires that cast-in-place parking structures be protected against corrosive deicing chemicals and leakage by a waterproofing membrane). An alterrnative to the hot-applied membrane has been proposed, of using a factory-made torch-applied membrane (overlaid by asphalt). There are advantages and disadvantages of a torch-applied membrane. Althpough we have designed many parking structures with a hot-applied membrane overlaid by asphalt wear course, we have not designed any with a torch-applied membrane and asphalt wearing course (we have though seen torch-applied mmebrane overlaid by concrete topping for loading dock ramps in a building).

QUESTIONS:

Has anyone had experience with torch-applied membrane overlaid with asphalt on roof level of parking?
How did it work out and how has it performed over the years?
Any problems with the asphalt attributable to the torch appled membrane?

 

[Ron]

ajk1....is this an SBS or an APP Modified Bitumen that will be torch applied?

This most significant issue I've seen with any torch applied membrane is surface preparation and workmanship. Also, many torch applied applicators (and manufacturers) will use "seam only" torching.....bad idea. Watch for it and don't let them.

For SBS modifieds, the melting point is lower; however, these usually have thinner reinforcing mats so there is less "asphalt" to melt.

For APP modifieds, the melting point is much higher and there must be care in keeping the material flowing under the torch.

Also, concrete will need to be consistently primed and be careful of "heat sinking"....large mass of concrete, cools quickly.

 

[ajk1]

Hi Ron - thanks for this information. I will have to find out if it is SBS or APP modified bitumen. Have you had any experience with these products when used under asphalt on roof level parking of a parking garage?

 

[JAE]

I'm not sure how this relates to Ron's comments - but we just did a parking garage with an occupied area below with a detail from Carlisle.
This is their CCW-500 product - found here.

It has a waterproofing product with a drainboard/protection board system topped with non-structural pavement.

 

[ajk1]

JAE - Thanks for this. what you attached shows a concrete topping. There is lots of this with a concrete topping. Our case is an asphalt topping. Have you had any experience with this, but with an asphalt topping?

 

[JAE]

I always shy away from asphalt toppings. Mainly because the asphalt always seems to crack/shrink a lot more and doesn't distribute wheel loads over the drainboard/protection board as well as concrete.

You could contact Carlisle (or any other similar company that provides similar products) and ask them about the asphalt paving vs. concrete.

 

[ajk1]

JAE - that is my experience too is that if the asphalt system is not done properly (i.e. too thin, not properly compacted, not the right asphalt mix, not the best materials, etc.), but in my area (Toronto) it is widely used in parking structures and is generally successful. We have done many such garages and the Toronto Parking Authority uses that throughout their parking stuctures, and they are performing generally well. The problem that I have when I have tried concrete topping, is that it is relatively expensive, it cracks which does not look good, water gets thru the cracks and lies under the topping, and is more difficult to remove to get to the membrane to repair leakage. By the way, in the asphalt system on parking garage floors, no drainage board is used.

I will follow up on your suggestion to contact a torched-on membrane supplier and go see at least one of their projects to see how it is doing. I had already asked the contracor to give us the name of at least one such project, but so far he has not got back.

Given that no one has yet responded with an answer that they do use torch applied membrane overlaid with asphalt wearing course on parking garage floors, I am thinking that that is not commonly done...but maybe someone will still respond that they do.

 

[ajk1]

Ron - the torch applied membrane being proposed by the contractor is an SBS birumen. It is
TP-180-FF-Base 3 mm thick, by IKO (we had specified 6 mm thick (i.e. 2 layer reinforced) hot applied rubberized asphalt membrane.

 

[ajk1]

Ron - sorry I made a mistake in saying in my post above that we had specified 6 mm. We had specified 3 mm.