Caulking Siding Flashing
Effective roof flashing around a chimney includes two layers.
Caulking siding flashing. Use around sinks tubs and showers. Simply apply this inexpensive filler into the cracks to seal. Getting the right sealant on your flashing is the best bet. Paintable silicone caulk can be used around the outside of window units to properly seal the window and the siding edge or around the entire door unit.
The nails holding up the siding should not be caulked. The flashing will channel the water moving down the unobstructed grooves away from the top of the 2 by 12 down the. Also avoid caulking tongue and groove siding boards together. Pieces of 18 inch wide flashing installed prior to the brick work but on top of the house wrap in a stepped fashion periodically laying on top of the lapped upper portion of the siding to get the water back to the exterior of the wall is more along the lines that i would be thinking of.
One laying involves tightly playing sheet metal around the chimney edges. Siding nails should not be caulked another item that needs room to play is siding boards themselves. In the second layer more sheet metal is inserted into the chimney mortar joints and folded over to cover the first layer. Paint works well over it.
Joint flashing butt joint horizontal lap treatment june 2014 james hardie does not recommend caulking butt joints or the horizontal overlaps joint flashing 6 in. Placing caulk over large portions of wood siding prohibits the natural movement of the wooden panels and can cause extensive damage to the exterior of your home. Many professionals like those at james hardie also agree that you should not use caulk on fiber cement siding unless there is no metal flashing underneath. Seal small cracks and gaps in your siding under 1 4 inch wide using an acrylic latex caulk.
Siding is often textured and if you slide the tip of the tube along the bumpy texture the bead of caulk will. Caulking here prevents water from resting between the siding and the 2 by 12. Do ride the smooth edge when caulking a seam between a window and textured siding. Use when installing bath fixtures to seal gaps between shower tiles between sinks and counters and around the base of the toilet.
James hardie also does not recommend applying caulk to the horizontal overlap between siding planks see figure 2.