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PermaBase Cement Board | Frequently Asked Questions
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Callers to our 1-800-NATIONAL® Technical Assistance Hotline frequently ask the following questions about PermaBase Cement Board:
 
 
PermaBase Cement Board
What thickness of PermaBase® should I use for my project?
Why is PermaBase available in different thicknesses? Or why is PermaBase available as a 1/4" and a 1/2" thick panel?
Where can I use PermaBase?
How do I cut PermaBase?
Which side should I use? Or should I tile a particular side of the board?
What type of fasteners should I use - nails or screws?
How often do I fasten the screws or roofing nails to secure the PermaBase?
I have to make a hole or "cutout" for my pipes. How do I do that?
How much of a gap do I leave between boards?
Why do I have to tape and finish the seams?
Do I need a vapor barrier behind PermaBase?
Can I use 1/4" material on walls and ceilings as it is lighter to handle?
What if I have a curved application? Does PermaBase Bend?
What type of warranty does National Gypsum offer on PermaBase?
   
  Technical Questions
Does PermaBase have a 1 hr and 2 hr fire rated assembly?
Does PermaBase have a flame and smoke spread rating?
What is the insulating or thermal value of PermaBase?
I live in an area that has heavy winters. Is PermaBase acceptable to use in freeze/thaw conditions?

What thickness of PermaBase® should I use for my project?
For residential walls and ceilings, you should use 1/2" or 5/8" PermaBase; for floors and countertops, you can use either 1/4" or 1/2" depending on your subfloor and the thickness of adjoining materials (such as the transition from tile to hardwoods). If your subfloor is at least 3/4" thick, then you can use 1/4" PermaBase; otherwise you will need to use 1/2" PermaBase. 5/8" PermaBase is also produced for many commercial applications.

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Why is PermaBase available in different thicknesses? Or, why is PermaBase available as a 1/4" and a 1/2" thick panel?
In flooring applications, it is important to match heights where there is a transition from one floor covering product to another. PermaBase offers 1/4" and 1/2" material for floor applications to ensure flexibility and a better transition from area to area. 1/4" PermaBase also works well for countertops to help maintain a minimal height impact when adding tile to an existing countertop.

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Where can I use PermaBase?
Traditional cement boards like PermaBase are extremely versatile and can be used in a variety of applications. PermaBase is perfect for interior uses such as floors, walls, countertops, or ceilings. It is also a terrific product for exterior walls and soffits for tile or stucco finishes. It is also an approved and frequently used product for saunas and steam rooms.

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How do I cut PermaBase?
It's a simple process using a straight edge, pencil, and utility knife. Once you have marked your cut, use the straight edge as a guide to firmly score the top mesh of the board (noted by the printing that reads, "Cut this side"). Snap the board downward and then use the utility knife to cut the back mesh leaving you with a clean straight cut. As with all cutting operations it is recommended that you wear eye protection such as safety glasses or goggles.

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Which side should I use? Or, should I tile a particular side of the board?
PermaBase products have a tapered edge on one face so that once installed and taped you have a level, uniform surface to adhere to with your finish treatment. Look at both sides and you will see printing on the side with the tapered edge. Install the printing side "out" so once installed you should be able to read the printing. If you find that you have installed PermaBase with the wrong side visible don't worry, tile and stucco adhere equally well to both sides of the panel.

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What type of fasteners should I use - nails or screws?
You can use either nails or screws to fasten PermaBase to your floors, walls, ceilings, or countertops. However, you will need to use either 1 1/2" hot-dipped galvanized nails (roofing nails) or 1 1/4" PermaBase coated cement board screws. If you are attaching PermaBase to 20-gauge or heavier metal framing, use 1 5/8" PermaBase cement board screws. Drywall nails and screws should not be used as they are not alkali resistant.

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How often do I fasten the screws or roofing nails to secure the PermaBase?
On walls and floors/countertops, attach fasteners 8" o.c. in each direction. On ceilings, attach fasteners 6" o.c. in each direction.

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I have to make a hole or "cutout" for my pipes. How do I do that?
Place the PermaBase board on a solid support surface. Mark the location on the PermaBase board to the size of the hole that is needed on the same side as the writing. Always cut the side with printing. Using a utility knife, score the cutout. Using a regular hammer, hit around the inside edges of the cutout. Tilt the board to allow the core material to fall from the hole and then cut out the remaining back mesh. A router and concrete bit may be used with a proper dust mask and, as always, eye protection.

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Why do I have to trowel out a setting bed or support bed before placing PermaBase on the floor?
The purpose of troweling out a 1/4" mortar bed or "support bed" is to provide a leveling agent for the plywood subfloor. Differences in height between pieces of plywood, whether it is from poor nailing, minor warping, floor joists, will affect the tile if not addressed. The best way to ensure a solid base for your tile application is to start with a plywood subfloor that does not exceed a 1/4" of variance for every 10' and to apply a 1/4" notched trowel bed of mortar in which the PermaBase is then set and then nailed or screwed.

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How much of a gap do I leave between boards?
When using PermaBase in a flooring or countertop application, boards should be spaced 1/8" apart. The gap will be filled by the mortar and alkali resistant tape to create a solid uniform tile substrate. Also remember to leave a 1/4" gap around the perimeter of the room to allow for subfloor movement.

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Why do I have to tape and finish the seams?
Taping and finishing the seams with a thinset or mortar and an alkali resistant mesh tape creates a uniform surface for your tile. It also helps prevent cracking in the tile due to subfloor movement such as thermal expansion and contraction.

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Do I need a vapor barrier behind PermaBase?
PermaBase is not a vapor barrier and an additional barrier is not required in most conditions. In areas such as indoor pools and saunas, a vapor barrier is recommended.

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Can I use 1/4" material on walls and ceilings as it is lighter to handle?
1/4" PermaBase is only for floors and countertops where there is proper support for the board. A minimum thickness of 1/2" should be used for walls and ceilings.

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What if I have a curved application? Does PermaBase Bend?
Our standard 1/2" PermaBase product will bend to a 90° radius at 5' and for tighter radii you can use PermaBase Flex. PermaBase Flex is a specialty board specifically made for curved applications. It is a 1/2" cement board that bends to 90° at a 6" radius. This is done without having to wet or score the material prior to bending it.

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What type of warranty does National Gypsum offer on PermaBase?
PermaBase has a Lifetime Limited Warranty on Interior Applications and a 15-Year Limited Warranty on Exterior Applications. Please click the following links for warranty details.

Lifetime Limited Warranty
15-Year Limited Warranty

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Technical Questions

Does PermaBase have a 1-hr and 2-hr fire rated assembly?
Yes, PermaBase achieves a 1-hour and 2-hour fire rating using approved assemblies as witnessed by the Underwriters Laboratories and Warnock Hersey. Click here to view these assemblies.

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Does PermaBase have a flame and smoke spread rating?
Yes, PermaBase has a flame spread of 0 and a smoke spread of 0.

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What is the insulating or thermal value of PermaBase?
1/2" PermaBase has an R/k value of .2/2.7 1/4" PermaBase has an R/k value of .1/2.7

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I live in an area that has heavy winters. Is PermaBase acceptable to use in freeze/thaw conditions?

Yes, PermaBase has been tested and passed 100 freeze/thaw cycles in accordance with ASTM C666 (Procedure B).

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