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Covering gypsum
timco	07-14-2009 22:33:35
Member Posts: 57 Joined: 11-15-2008	Looked at a 1000sf job to polish on sixth floor of 80 year old bldg, not possible cause floor has 1-1.5 inches of gypsum over concrete. Gonna turn them to overlay/stain/seal, but in 26 years never worked over gyp. I know some bag products say dont use over gyp. Any suggestions based on prior experience? Thanks, Tim

BARRETO	07-15-2009 18:23:01
Member Posts: 16 Joined: 07-07-2008	Hi, When you refer to gypsun, I assume your refer Plycem or something similar like a concrete panels or just regular gypsun as dry wall?

timco	07-15-2009 19:47:25
Member Posts: 57 Joined: 11-15-2008	No, the floor itself is apparently gypsum underlayment over poured in place concrete. This particular area shows mastic from past tile, but currently has parquet directly on the soft, chalky, inch thick layer. The exterior walls are gypsum interlocking panels, so I assume the flooor is poured in place gypsum.

BARRETO	07-17-2009 16:35:07
Member Posts: 16 Joined: 07-07-2008	Well, for nasty jobs I have used extreme overlay from surecrete, but personally I would never go on top of this material, especially when you mention chalky areas, I would be concerned with bonding issues, once again this would be my personal opinion, not sure if there are other methods, With extreme Overlay I would not be concerned of cracks or flexion strength, this product is great it holds up to 10000 PSI, it’s designed to go over asphalt, only problem is the price, it’s a bit expensive. I have done crazy jobs like, going on extremely damaged concrete, going over tiles, over wood, etc. but the client has to understand the risk of bonding issues, cracks, etc, and has to take the responsibility for any of this issues. Now, even if the client takes the reasonability for all of the possible issues that could happen, a failed floor, even if the client is responsible, it would be a bad impression to another person about your company. So consider it, my personal option would be removing it, and if there was a possibility of an overlay, it would be Extreme Overlay.

ptspurlock	07-19-2009 13:02:29
Member Posts: 1 Joined: 07-19-2009	Hi Tim My name is Paul Spurlock I'm new to this forum with no previous posts. My company has experience installing self leveling underlayments and toppings. For your future reference, there is a product , Ardex GS-4 a self-leveling repair underlayment for distressed gypsum and wood sub floors. However, parquet does not meet there code approved, structurally sound plywood, OBS, and strip flooring. If you remove the parquet first and remove the (non-water-soluble) adhesive down to a thin film well bonded residue by wet scraping. From past experience, the wood adhesive is probably stronger than the gypsum substrate and most will stay attached to the wood. It a dirty job but if it can be done. A couple laborers with Bosch hammers equiped with a 2”wide sharp scraper blade is the most effective way to remove parquet. Try not to scrape real deep as GS-4 has a 2” depth limit without aggregate. 5 “ with aggregate. The Ardex GS-4 is not a permanent wear layer, it is self leveling underlayment. Simply apply an integrally colored or stained Micro Topping and seal. I use Ardex SD-M micro topping and market it as Ardex Designer Floors. You are welcome to access this link and review an image of an Ardex Designer Floor @ the Ardex Training Center I could not get my URL to post in the company profile page. If you want more information about any ardex product use this URL and scroll down to the GS-4 article http://www.signature-concrete-stain.com/self-leveling-floor-compound.html After further review of this page I haven't posted a complete page on this product. If you go forward with this project and need additional information I can write a page just for GS-4 or email a pdf file. ptspurlock

timco	07-24-2009 23:14:43
Member Posts: 57 Joined: 11-15-2008	Thanks, Guys. Still working out the details.

MC	07-25-2009 08:53:56
My Gallery Member Posts: 1655 Joined: 05-20-2007	Hey Paul, how do you like the sd-m? I like Ardex products and think the SD-M is real easy to work with but I dont have any long term jobs with it. Have you ever had any issues with it being too soft and easily denting or various things leaving impressions in it after its cured?

hlg	07-27-2009 19:30:51
My Gallery Member Posts: 391 Joined: 11-15-2008	Hey Tim You may want to check the psi of the gypcrete, some of it is very soft. We are doing 6,000 sq ft of gypcrete (Dura-cap by maxxon) then topping it with two coats of thin-finish and staining. If it is a soft gypcrete you may want to spike roll it first to be able to grab on to it with your topping. If it's less than 2500 or 3000 psi you will probably have a delamination problem. Harry

Envirocrete	01-24-2010 16:20:13
My Gallery Member Posts: 15 Joined: 05-23-2007	Thought we should give our 2 cents on this one. We have installed quite a few SD-M jobs over existing Gypcrete surfaces (old and new). There are a few things to keep in mind thought: 1. Patching: The surface should be sanded prior the the installation, any cracks or spalls should be dampened & patched (Ardex Featherpatch). 2. Priming: We typically dampen the floor, apply 1 broomed in coat of 3:1 dilute acrylic primer, apply a 2nd coat of 2:1 broomed primer followed by final coat of 1:1 primer. 3. SD-M Application: Once the final coat of primer is dry (minimum 4 hours or next day) we apply a tight troweled (translucent) application of SD-M, allow it to dry (typically a couple of hours), apply a 2nd coat of SD-M with a magic trowel, once dry (next day) use a sanding screen (60 grit) to smooth the surface, clean and apply a 3rd tightly troweled (translucent) coat of SD-M. Allow to this final coat to dry (next day) and apply any stain and/or sealer you desire. We typcally use 1 bag of grey mixed with 1 bag of white to create a nice standard grey concrete color (see picture)

victor.pachade	02-11-2010 17:33:30
Member Posts: 39 Joined: 10-22-2009	Param 5500, Pentimento and Sgraffino have been extensively used over Gypsum. In fact there is a post in this forum...it describes spraying Sgraffino Superfine over gypcrete and acid stain it after wards.

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