The rain cap/screen on my chimney blew off recently and I’m considering replacements. The chimney is made of concrete block with an oval tile flue and a bright red synthetic stucco outer coat. There is a concrete cap in good condition, i.e., no cracks, proper slope. The problems I am hoping to prevent are 1) critters from flying down the flue and 2) having whatever I put up there blow off. We have 60+ mph winds on a regular basis.
My current plan is to build a form and cast a shallow hip roof rain cap out of concrete with rebar legs extending from the underside down to rest on the cap and with steel strapping attaching to the flue. Expanded metal mesh or hardware cloth will be secured to the rebar to deter wildlife. The old, rain cap had some flimsy clamps which tightened on to the top of the flue and ended up being pretzel shaped after launch. I don’t want to crack the flue with point pressure, so I’ll form the strapping to act like a hose clamp around the exterior of the flue and probably use some sort of padding between the steel and the flue. I’m hoping the mass of the concrete coupled with the shape and attachment to the flue will secure it in the wind.
I don’t have to deal with a lot of rain, just snow, hail, sun and wind. The location is Southwest Montana. The chimney currently serves a propane stove, but that is going to be replaced by a wood stove after installation of a boiler/radiant floor system this summer.
Any suggestions for more wind resistent features?
Replies
For our flue, to keep the critters out, I fashioned a 5-sided box (open bottom) out of expanded metal mesh. SIzed it to fit fairly tightly around the protruding clay liner, then fastened it with several spiral duct clamps (giant hose clamps), linked end-to-end.
If you're the sort that feels you MUST have some sort of a rain shield, it wouldn't be hard to fasten some tin to the top of this sort of gizmo.
Spousal Aesthetics
The rain cap is really just for looks, which my wife is concerned about. The mesh is the functional part. The previous arrangement was expanded metal on 4 sides with a sheet metal top. Poorly made and frankly very cheap looking. The problem with wind is real. The chimney is on the outside of the house facing the prevailing wind, so the cap gets hit not only with the direct wind but also air moving up the house. Thus the mass of a cast concrete cap coupled with stout attachment appeals. Also the construction meets the rocco standard of being insanely complicated, as well as being a permenant solution. I don't like having to do things over and over. Overthink the problem, screw around overbuilding and then move on to the next obsession.
Da rain cap onna barn done blowed off last fall.
wut to du?
wleded up sum ol' steel auto wheels wit sum rebar holdinem togeder an' a piece os sheet emtal rufe, couple uv pices of rebar pokin' down inna chimmeny, it been gud since...