The Roofing Resource Blog

Avoid Common Mistakes When Installing Hardie Siding

Tue, Mar 4, 2014 @ 06:33 PM | Perry

Here are 5 tips to ensure you James Hardie siding project looks great and lasts a long time. 

Hardi Siding Indiana1. Order the project the way you are going to install it.

When you measure the home or building for Hardie siding and trim avoid ordering job solely based on Sq Ft. of siding and Ln Ft. of trim. Walk the job and order the project based on how you want to hang the siding and trim. Plan on using full sticks of trim wherever you can then and count pieces. Using two pieces of trim on one side of a window or door is as unsightly as having excess but joints on a section of wall that could have had all full length pieces. 

When measuring for Hardie siding don’t subtract sq footage for entry doors, garage doors, or windows and figure the area of the gables as base x height x .75.  Remember that Hardie needs to be broke on studs and this will generate more waste add 5% -7%  and order your job. 

You will almost alway come up with slightly higher material counts like this but in most cases extra material can be returned and your job will look much better installed with clean, full pieces of siding and trim rather than pieced together.

2. Get off to a good start

If you are completing a Hardie installation on new construction project you can easily measure off the new block or concrete foundation to find a level line and starting place. But if you are doing a re-side of an existing house or building check how well the existing siding matches up on the corners all the way around the structure before you start taking it down. If the existing siding was hung correctly and matches up, you can use certain pieces to get quick level lines on the wall that you already know are right. You can use the first piece of the existing siding to get a level line for your new starter course. It doesn’t matter if the old siding is a different height than the new Hardie siding, you can still measure off a line you know made it around the home or building and matched up. 

Putting on the first two or three courses of  Hardie siding all the way around the home before you lay up an entire wall is never a bad idea, neither is making reference lines after several course high just to make sure corners come out right. 

Helpful tip 

3. Cutting Hardie Board Siding

Cutting Hardie siding isn’t hard but it does have it’s tricks. Using a circular saw with a blade made for cutting wood will generate huge clouds of very dangerous dust. The dust contains silica and is terrible to inhale in any amount. Hardie Makes blades for circular saws especially for cutting the fiber cement board that greatly reduce that amount of dust it creates but you will still need safety glasses and a dust mask. A very simple way to cut Hardie siding is the score and break method. Using a utility knife you can score several times in both directions the line you want to cut. Once the piece has been scored enough it will bend and break in a clean line. This method doesn’t require any special tools and is dust free but it takes some time to make cuts. 

Another way to cut Hardie is with a guillotine type cutter that is hand powered and dust free. It’s sheer is connected to a lever you pull down and through the Hardie. It makes clean and accurate cuts but a tool like this can cost $600- $800 and it is very stationary. The Hardie has to be brought to the table where the guillotine is located. 

Our Hardie installation crews have had very good luck using a handheld sheer to cut Hardie siding. The sheers are small, portable, cut fast, and dust free. Each sheer cost around $275.00 and will last for several years of hard work.  

4. Hanging Hardie and Butt Joints 

No matter how good you are at cutting Hardie siding you should avoid hanging cut ends in the middle of a wall. Make a habit of putting factory edges to factory edges and at butt joints use a piece of flashing behind joint to keep water from traveling behind siding. You can cut pieces of felt paper, painted aluminum coil stock, or pieces of house wrap. We find it just a cheap and easy to buy a flashing called bear skins, it’s like a large post it note with a sticky tab that adheres to the wall behind the butt joint. It really doesn’t matter what you use as long as you use something. 

Treating butt joints with caulking will only make a mess of your new siding and will not be a long term solution. Place factory edges to factory edges and use a flashing behind the butt joint and you will be fine. 

Hardi       Hardi Siding

5. Properly Nail off The Siding  

You can shoot Hardie siding on with air powered nailers or use hand driven roofing nails to attach siding to the home or structure. The nails can be ringed- shanked or smooth just make sure you are hitting the studs in the wall. Place a nail in every stud especially is they are 24” on center and ensure that nails are between 3/4” to 1” below the top of the piece of siding. Nails drive in too high won’t hold as won’t nails that are over driven. Drive nails  flush with face of hardie plank but don’t counter sink nail. 

Our Crews prefer 1 3/4 “ smooth shank roofing nails for Hardie installation. If we do make a mistake and have to move a piece the smooth shanks are removable unlike a ring-shank nail. 

Topics: Siding