# Underlayment substitution request

**URL:** <https://forum.4specs.com/t/underlayment-substitution-request/2690>\
**Category:** Archive - Specifications Discussions #5\
**Created:** [October 28, 2014, 1:05pm UTC](https://forum.4specs.com/t/underlayment-substitution-request/2690 "2014-10-28T13:05:45Z")\
**Posts on this page:** 4\
**Page:** 1

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**Author:** ![rhinkle](https://yyz1.discourse-cdn.com/flex047/user_avatar/forum.4specs.com/rhinkle/32/179_2.png) [@rhinkle](https://forum.4specs.com/u/rhinkle)\
**Post date:** [October 28, 2014, 1:05pm UTC](https://forum.4specs.com/t/underlayment-substitution-request/2690/1 "2014-10-28T13:05:45Z")

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We have a senior living housing project, 3 stories, concrete plank floor. After the stud walls are installed, a gyp / concrete floor underlayment will be installed. We specified a 4000 psi product. Owner wants to entertain cost savings options and they are interested in looking at 3000 psi options. It’s been a while since I have done this type of overlay and feel like this is not a good idea, but need technical reasons why.

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**Author:** ![nwoods](https://yyz1.discourse-cdn.com/flex047/user_avatar/forum.4specs.com/nwoods/32/215_2.png) [@nwoods](https://forum.4specs.com/u/nwoods)\
**Post date:** [October 28, 2014, 1:56pm UTC](https://forum.4specs.com/t/underlayment-substitution-request/2690/2 "2014-10-28T13:56:20Z")

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4k products are kinda rare. They are usually in the 2-3k range. I have specified and installed this one on many Multi-family and office building floors, with no problems: Hacker Industries Firm-Fill 3310

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**Author:** ![spiper](https://avatars.discourse-cdn.com/v4/letter/s/dfb087/32.png) [@spiper](https://forum.4specs.com/u/spiper)\
**Post date:** [October 28, 2014, 2:07pm UTC](https://forum.4specs.com/t/underlayment-substitution-request/2690/3 "2014-10-28T14:07:22Z")

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I have limited recent experience with this type of underlayment as well but in my experience this was typically a 3,000 psi type product in our area.

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**Author:** ![justatim](https://avatars.discourse-cdn.com/v4/letter/j/f0a364/32.png) [@justatim](https://forum.4specs.com/u/justatim)\
**Post date:** [October 29, 2014, 11:18am UTC](https://forum.4specs.com/t/underlayment-substitution-request/2690/4 "2014-10-29T11:18:27Z")

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If the facility’s operation requires rolling medical equipment (with those itsy bitsy wheels and heavy load) along the floor, I would insist on cement type with high psi. The lower strength products (usually gypsum) can rut from the concentrated rolling loads.  
One hospital that I trouble-shooted had this problem; the solution was to remove all the sheet flooring and replace the underlayment.  
For predominantly residential loading, the lower psi should be OK.