Monday, January 31, 2011

Installing Vinyl Siding - Screws vs. Nails

I've had people ask me why I'm using screws instead of nails to install my vinyl siding.  Nails work fine when you're attaching to a plywood sheathed or OSB sheathed, conventionally framed wall. 

However, because I'm attaching to a plastic web that's embedded in the ICF wall, I need the extra grip that screws will provide.  I've heard of people using nails to install siding on ICF walls, but I just don't think a nail has enough holding power when driven into plastic. 

Just my opinion of course; but I'm sticking with screws.

Friday, January 28, 2011

Siding Mockup

I've built a small mockup of a wall section so I can make sure my siding installation fits together as planned.  I started with a scrap piece of plywood, covered it with housewrap, and then added two plywood strips, the same as I used outside.

The first step is to install the bottom bug screen. The bug screen prevents bugs from getting up inside the airspace between the housewrap and the siding, but will still allow moisture to drain out.  There will also be a bug screen at the top of the wall.
I'm using a strip of fiberglass window screen about 10" - 12" wide.  I pull the bottom edge of the furring strips away from the wall just enough to slip about 4" of the screen up between the plywood strip and the housewrap. Then I fold the screen around to the front of the strip, and then fold it down on top of itself. Finally, I staple through the front folds into the plywood strip to hold it in place. The bulky folds of the screen will hold it tight enough to the back surface of the siding to stop bugs from getting through.  

The next step is to cut a slit in the housewrap just below the plywood furring strips.  The top edge of the flashing goes up through that slit and behind the housewrap.  The flashing will be screwed every 16" into the plastic webbing embedded in the ICF wall.  Any moisture that comes down the face of the housewrap will travel over the flashing and drip onto the ground. 

Once the flashing is in place, then I attach the starter strip to the wall. The starter strip is the component that the bottom row of siding clips on to. It will be screwed through the plywood strips and into the plastic webbing inside the wall.

 You can see the "S" shaped bottom edge of the starter strip here.  The bottom edge of the first row of siding will clip around that "S" shape, holding the siding to the wall.

The next step is to install the bottom row of siding. Vinyl siding isn't really difficult to install, but there is one thing that's extremely important to remember: Vinyl siding must not be attached tightly to the wall.  In fact, vinyl siding isn't so much "attached to" a wall, as it is "hung on" a wall. The screws cannot be driven in tightly, in fact they need to be driven in so that there is approximately a 1/32" gap between the screw head and the siding. (That's about the thickness of a dime.)

The reason for this is that vinyl siding expands and contracts with heat and cold. If it is attached tightly to the wall, it will buckle when it expands in the heat of the summer. When this happens, it's very noticeable and looks terrible. So, it's extremely important to leave that gap between the head of the screw and the siding. Also, the screws should be placed in the center of the slots so that the siding can move freely in either direction.

To install the first row of siding, the bottom edge of the siding is first clipped under the bottom edge of the starter strip, and then the top edge of the siding is screwed to the plywood strips. The next row of siding follows the same principal; the bottom edge of the siding is clipped under the top edge of the siding below, and the top edge is screwed to the wall.

 Here you can see how the bottom edge of the siding clips around the top edge of the row of siding below.

When the siding is finished, I'll install a trim board (called a water table) underneath the flashing on the bottom.  In this case, the water table is strictly cosmetic, it's only purpose is to give some definition to the bottom edge of the siding, separating it from the bare area on the bottom portion of the wall. 

Wednesday, January 12, 2011

Housewrap and Rain Screen Inspection

I've finished up the housewrap and rain screen and had my inspection done.  The inspector was happy and I can proceed with my siding installation. 

You can see a couple of areas in the photographs that still show bare plywood.  Those of course will have to be covered in housewrap first, but I explained to the inspector that I would like to do the housewrap and siding all at once while I have the scaffolding set up, rather than do the housewrap and then tear down the scaffolding only to have to set it up again to install the siding.  He had no problem with that, and it will save me some time in the long run.