After the first of the year I will be replacing siding and fascia boards on my house, the original ones are showing there age. My qeustion is, what type of nail gun and what size nails to use? I have a good compressor, borrowing scafolding, and pre painting the boards before installing. I plan on using HardyBoard sold at Lowes, I believe that's the stuff made out of cement? Correct me if I'm wrong or recomend a better product, thx

also, it would be great if the nail gun could be used to build a fence also

hardiboard is great once it is installed. it is brittle, heavy and usually takes two people to install, use a bostich flush nailer with #6 and #8 galvanized nails so they wont rust. if you use hardiboard go ahead and get the high dollar blade made for it or you will probably wish you had, it will burn up regular blades in a hurry. you can use the nailer for fencing.

That's what I wanted to hear, and thx for the heads up about the blade. The hardiboard instructions say not to countersunk the nail head, should it be left just above the surface?

just flush with it. you can adjust the air pressure to get it to just set flush with the siding.

stay a couple of inches from the edges when nailing they have a tendency to break

I have the Duo-Fast coil nailer that is designed for everything you mentioned. Its a bit more money, I think, but adding this as another option. Owned it and built many many many projects and only had one/1 jam.

Kinda like a Ford/Chevy debate, huh?

get a paslode framing nailer, used them for over 30 yrs. and hung a ton of hardiboard with them. can buy the nailgun at lowes and the nails are easy to find, generic are good but the paslode are a little better. use 8's only for hardi as 6's dont have enough holding power in the wind or for the weight. set the air to about 70# to start and use a practice piece to fine tune and flush the nail and no do not countersink them it breaks the back out and makes the nail worthless. stay at least 1 1/2" below the top edge if running the horizontal siding and if using 4X8 sheets you need to be very careful when shooting the edges as you have to stay real close to them. for the soffit you can use 6's and they work fine. it will take 2 people to hang the boards as they are hard to manage solo and will break easily if they flex too much. you might want to look at putting up the blue foam insulation on the exterior before hanging the siding and adding the insulating factor to it, its well worth the money if you seal the joints with tape, use 1/2" and the 8's still work just fine or you can go to 10's.
be sure to use some calk at the joints of the hardi as you hang it, calk then butt joint, wipe excess. pre painting is good but your gonna have to add a coat after its hung to cover marks and calk.

most nail guns have a flush nailer you install on the tip
air pressure can be anything as long as the flush nailer is installed

i don't think you want to countersink Hardi board
but i can be wrong

I do this stuff for a living. I use a paslode 2" 16 gauge finish nailer put 2 nails ever 12"oc . Put it up own several 1,000,000.00 homes.

Have not had any problems with this and be sure and buy the blade that cost about 50.00 dollars
And wear a dust mask when you are cutting
http://www.jameshardie.com/pdf/install/hardietrim-fascia-hz10.pdf

We always use a coil nailer with 2.5 in. galvanized nails. There are several ways to hang it, its more important to always remember to stay away from the edges cause Hardi is brittle and will break. The stuff is heavy also so use another person to help. Its easy to hang, just get a good hardi blade/diamond blade to cut it with and some people like to wear a mask to avoid the dust.