# Easiest way to cut HardieBacker 500 Cement Board



## drewdin

I have been putting in a bunch of HardieBacker 500 the last few days, that stuff is like steel. It states in the instructions that you scour it with a knife and bend to break it.

I'm not sure if anyone has tried this but it does not work, i tried scouring both sides and it didnt help much. The only thing that worked was using a sawzall and a metal cutting blade, the only issue with that is that I went through five blades on three sheets along with the instructions telling me not to because ti creates harmful silica dust. 

There has to be an easier way, does anyone know of one? Thanks


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## nealtw

You can get a blade for the circular saw. There are shears that you can rent.


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## drewdin

is there a specific blade or shears you can recommend?


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## nealtw

The blade is a diamond blade that says cement board on it. A regular concrete diamond blade will work. Get a dust mask!!!
Havn't used a shear, only seen others use them, messy cut would want to be hiddin behind trim


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## inspectorD

I always just use a utility razor knife and it cuts fine. Even when it wears down just apply more pressure. Or you can use the carbide tipped knife they sell, it more or less just scores the sheet.
A skillsaw and blade is a real mess maker...beyond dust! I have also used a jigsaw with a carbide blade to cut the circles, or arches in doorways.


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## Fireguy5674

The carbid tipped scoring tools they sell work pretty well.  With two or three passes they will allow the cement board to snap pretty evenly.  Since you are supposed to tape and mud your joints before applying tile any edge variations will be filled giving you a solid base for your tile.  If you are making ANY dust wear a mask.  You will be happy you did.  It may take a number of years but that dust will come back to haunt you.  They make a saw specically designed to cut cement/hardie board.  It has a dust collector built into it.  You might be able to rent one but they are kind of pricey for a single project.


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## Jaz

Drewdin,

Many people have trouble cutting Hardie because they use the common sense technique to cut it.  They try to cut it like drywall.  Wrong!  Re-read the directions.

You need to score it several times with the carbide scoring tool, then snap up, not down.  

Alternatively you can cut it with a 4" side grinder equipped with a basic diamond blade, but lots of dust.  Do it inside the garage near the door with a fan blowing behind you to minimize the dust.  Wood pallet on the floor, board on pallet, just lightly score then snap.  Still wear a proper mask.

Or if you do this often get a pair of the special shears.  

Doing a floor?  Why 1/2"?

Jaz


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## drewdin

I have a half bath and the floor is exactly 1/2" less than the adjacent wood subfloor. I was using the 1/2" hardie to build up the bathroom floor to the same level as the wood subfloor. That way when the wood goes in it will be the same height as the tile, or pretty close.

Do you have any other recommendations? Thanks


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## Jaz

> Do you have any other recommendations?



Yes, don't eat yellow snow!  

If you have any other questions, you know where to ask.

Jaz


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## drewdin

haha, that's what I saw when people ask for tips!


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## drewdin

I used the 1/4" today and it was much easier to use. do you recommend screws or roofing nails along with the modified thin set? Thanks


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## Jaz

Hot-dipped roofing nails work great, are faster, and cheaper too.

Jaz


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## CallMeVilla

I bought a used inexpensive Skil Saw ($20) and fitted a masonry cutting blade ($4)  ...  Draw your line and zip it off.  Done.  MASSIVE DUST  ...  wear goggles, ear protectors and dust mask.

For cutting holes for toilets  ...  4" grinder with a diamond blade  ...  works like  magic to sculpt the hole precisely.

TAH DAH!


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## drewdin

I tried using the roofing nails and three bent before they went into the hardiebacker. I ended up using the screws


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## nealtw

There is a screw made for that stuff.


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## Jaz

drewdin said:
			
		

> I ended up using the screws



And which screws would that be?  



			
				CallMeVilla said:
			
		

> I bought a used inexpensive Skil Saw ($20) and fitted a masonry cutting blade ($4) ... Draw your line and zip it off. Done. MASSIVE DUST



I highly do not recommend doing that.  Pallet on garage floor near door, Hardie on pallet, 4"grinder with diamond blade, just score Hardie, no need to go all the way.  Have a fan run behind you blowing dust out.  Mask & googles would be nice and recommended.

Jaz


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## drewdin

I used the scoring knife and the Hardiebacker screws)

I do have a separate question on how much compression there should be between the hardie board and the subfloor? Using the 1/4" trowel would leave a 1/4" of space but using the screws it pulled it tight when the heads went flush with the board.

What is the proper way or better, how should I properly set the hardie to the subfloor using modified thinset and screws? I'm securing the 1/4" in a few days, i am going to try to use the roofing nails again as my thoughts are that since it is thinner the nails wont bend, they might actually go through the board.

Thanks guys


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## Fireguy5674

Friend of mine does a lot of tile and he uses a roofing gun to secure the hardboard to the floor.  Much faster and cheaper than screws.  

As far as the space between the board and the floor goes if the board pulls tight to the floor that is fine.  All of the thinset will not leave as there is no place for it to go.  Just try to set the board in the thinset evenly so you maintain a flat surface for the floor.  The thinset under the board fills any voids where the floor is not perfect and adheres the board to the floor so when you apply tile the board will not flex or move.  Movement is what kills tile, cracks ext.


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## drewdin

Thanks for the info, i have a framing nailer, i wish i had a roofing nailer! I am going to try to use the roofing nails I have with a hammer, I'm kind of a ocd perfectionist so I will probably flip out trying to make sure everything is level with every hit. wish me luck!


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