Commercial roof membrane cleaning

Feel free to move this to the appropriate section of the forum.

We were asked to bid on a one-time cleaning of this roof. It is white membrane roofing, fairly open, 25,000 sq ft. Membrane manufacturer says: “sponge mop or brush, simple green, or as last resort, low pressure washing [they don’t specify a PSI]”. I tested a section with white pad, dawn, and a rinse that came out well, except for what appears to be grey mold spots. They are only where water can collect; not on parapet (about 24" high), or high spots or wrinkles in the membrane. Any ideas? Anyone do a project like this? The photo is not the exact roof, but identical material. Thanks in advance.

I really have no idea, my advice would be trying to figure out how long you think it will take and then allow for some time overage. So if I was bidding it I’d figure what I thought it would take and then multiply by 1.5. These odd projects always seem to take longer than anticipated. Good luck!

Piece of cake. I’d use a weak house wash mix and around 300 PSI. Make sure to inspect all seams before and after. Also make sure all your drains drain. Have a couple of foam squeegees to push water out of those low spots - generally that’s where you’ll see the mold.

And don’t forget sunglasses. That white roof added with the reflection of water will give you a headache quick.

why clean it?

Money :slight_smile:

Be very carefull a lot of membrane roof’s are not supposed to be walked on and are easily penetrated… I would stay away from pressure washing and just use a white pad on a doodle swivel on a pole, whatever soap you choose and rinse… pressure washer may give the dreaded fan effect…

I’ve seen a number where a walking path for service personnel was defined by attached “runners.” It may simply have been for safety reasons, because there are typically low areas where water collects. They have all been consistently sturdy in my experience.

I’ve done this before. Low pressure with a dual lance wand to remove some of the mold and debris. Then use a truck brush on a pole withj simple great to remove the black staining. Then rinse with your machine. It cleans up nicely. Just don’t let the simple green dry on you.

Thanks a million. Any ideas on pricing?

For pricing, I’d just think about how long it’ll take, plus the difficulty of dragging PW hose over the parapet, plus the cost of the Simple Green (you’ll use a lot of it). Since the roof is already wet from spraying up the debris, you can just pour the Simple Green on straight and push it around with a brush. You might be able to use a stiffer push broom or find a wider brush than a truck brush with soft bristles if a push broom doesn’t work.