Gilles' Outlet

March 23, 2009

Repairing a Chimney Cleanout Trap

Filed under: Masonry — Gilles @ 2:05 am

A 30 years old rusty chimney cleaning trap is removed. Rust protection is applied. A fresh coat of exterior paint is sprayed. The trap is re-installed with mortar. 


Skill Level: 2~3 (Basic ~ Moderate)

Time Taken: About 2~3 hours

This 35 years old house is equipped with a wood burning fireplace. In order to facilitate cleaning, some chimneys offer a cleaning trap. In this article, we give an old rusty trap a new life.

The subject of this article. An old, rusty chimney cleaning trap. Rain has started to carry rust away from the metal and bricks under the door are stained with rust marks. The door closes but no longer latches. On high winds days, it swings free and hits either the siding of the house (left) or its metal frame.

When I first noticed this problem, my initial reaction was to replace the trap with a brand new, stainless steel door. I found some cast iron replacement doors online starting at about $40 (including shipping and handling). Stainless steel doors were significantly more expensive. I eventually decided to go with a quick and inexpensive repair instead because:

  • I can give this door a new life for under $10. This is important in the current economy,
  • The current door is slightly bigger than 8’’ x 8’’ but smaller than 12’’ x 8’’. I could have enlarged the opening to accommodate for a new door but that would have been more work,
  • After repair, the door will function as if it was new (i.e. it will latch, no longer rust and stain bricks and even look significantly better),
  • The repair will not prevent a brand new door to be installed later.


During my research, I noticed that this vendor offered the largest choice : I wished I found an insulated, aluminum cast air tight door but I could not find any.

I am in no way linked to that vendor. I do not endorse it nor receive any compensation to mention it here. It appears as a “note to self”, a way to remember where to look at first if I ever decide to replace the door. 

Left: I swung the door open. This revealed a large amount of ashes in the chimney pit. This will be addressed later. After inspection, it looked like the door was set in a bead of mortar. I could not find any fastener.  


Right: I inserted a pry bar under the metal frame and gently pried away. The entire door assembly came loose very quickly. There was not much holding the door to the building.

Left: The opening after I removed the door. The mortar bead is clearly visible at the bottom and left sides of the opening.


Right: I knew it would take a while to eliminate the rust and paint the door so I taped a piece of 6 mil polyethylene around the opening. This will discourage critters and keep rain away.

It turns out, the wind blew my patch away the same day. Oh well, next time, I’ll find a better cover mechanism.

Left: This detail of one of the hinges of the door best illustrates how much rust was on the door. There is really not a single square inch without rust. There are spots of loose rust.


Right: I had a hunch that removing the door from the frame would make rust neutralization and painting much easier. I used a pair of “channelock pliers” to carefully  bend the frame part of the hinge. It took about a minute to separate the door from its flange.

Left: I purchased that can of rust neutralized years ago for another project. I did not see any preemption date so I assumed it was still good. Judging by weight, the can felt about half full.

I carefully read the instructions before doing any work. That specific brand of rust neutralized demands loose dust to be removed by sanding with 80 grit sand paper and requires rust on the metal to bind to it. Instructions clearly warned that the product will fail to perform if there is no rust left. Finally, instructions called for using the product when temperature is above 40F.

In my experience, it never pays to ignore manufacturer’s instructions.


Right: I used a power sander equipped with 80 grit sand paper to remove loose rust. I made sure to wear a respirator.

Left: It was cooler than 40F outside so I move inside, in a well ventilated location where I did not mind the overspray. I sat all parts on a set of ceramic tile scraps and sprayed as per manufacturer instructions (between 8’’ to 10’’ away from the surface, in a continuous movement). I applied two coats, within 20 minutes, as required by the manufacturer.

Right: Once applied, the product needs to dry for at least 24h. After drying, all the visible rust turned black. This is expected and explicitly described in the instructions. At this point, parts can be directly top coated with an oil based paint.

Left: The manufacturer also describes that a smoother finish can be obtained by lightly sanding parts with 400 grit sandpaper. The black part needs to remain for the parts to be protected from further rusting. I sanded as described on the instructions.  


Right: Tools for spray painting. From left to right: a respirator capable of blocking some VOC, a spray can handle and a can of exterior paint.

The handle presses the can’s tip and saves your finger for getting numb. I once sprayed a door (about 2 cans) and my index finger got numb for three weeks so I purchased this inexpensive (~$5) handle.

Left: I read all instructions on the can of paint and respected it to the letter. They call for a 12’’ spraying distance, two or three thin coats in 20 minutes and 24h drying time at least. I sprayed and left the part dry overnight.


Right: Meanwhile, I went outside and concentrated on cleaning the ash pit. By judging at the amount of ash, it appears that it was never cleaned in the 35 years this house has been standing for.

I first started to clean with a shop vacuum cleaner but wood ashes were so small, they clogged the filter almost immediately. After cleaning the filter three times in less than 3 minutes, I decided to scoop most of the ashes and then finish up with the vacuum cleaner. It took about 35 minutes.

Left: After all was said and done, about two 35 gal trash bags were filled with ashes, partially burnt pieces of papers, burnt poultry bones …, yuck! I will later put those bags in a heavy duty contractor trash bag (3 mil thick at least) so they do not burst open easily. I my community, ashes can be disposed in the garbage.


Right: After the door dried, I re-assembled it. I also took a minute to adjust the latch: a tongue of metal fitting in an opening of the frame. This fixed the non latching problem. As I did this, I made a few minor dents in the paint on the hinges.


Nevertheless, the door looked almost new. A few dust particles got caught in the paint (I should have been more careful containing dust from another project I worked on as the door was drying) but I was not concerned about those tiny imperfections. From where it is installed, no one will see them.

Left: Re-attaching the door to the masonry opening first requires the removal of all loose mortar. I used a brick setter’s hammer to gently hammer out any loose material. I also removed all dut, ashes and other debris. This will help the new mortar to bind to the existing structure.


Right: A bag of “SAKRETE – Type S High Strength Mortar Mix”. It is designed for brick settings, among other things. I purchased that bag a while ago and kept the leftovers (a few pounds) in a dry location. I scooped some of the mix in a 1 gal buck.

Left: I always mix concrete by adding a little bit of water a time. Too much water weakens the concrete. In fact, the drier the mix, the stronger it will be. There are of course exceptions to this rule. 


Right: After a few minutes of mixing, the concrete reached the texture of a stiff cake icing.

Left: A tool specifically designed for setting bricks. This narrow trowel makes it possible to pack mortar in between bricks. I purchased it as part of a “masonry kit” at a discount tools shop years ago. I have never used it before and it still has the manufacturer’s sticker on the handle.


Right: I used a water sprayer to wet all surfaces. This promotes good bond between the old mortar and the new mortar. It also removes all traces of dust. All masons I know never skip this step.

Left: The trowel is ideal to fill this joint. It is sometimes a little tricky to load the mortar on such a small trowel so …


Right: … the best way to repair a joint is to load a margin trowel with mortar and use the joint trowel to pack it in the joint. This operation is sometimes called “tuckpointing”.

Left: The joint filled. In theory, after filling the joint, masons make one last pass with another thin trowel shaped as a half moon. This creates a small recess in the mortar. I do not own this special trowel so I achieved the same result by wetting my finger and using it to smooth the joint as one would smooth caulk. Mortar attacks skin so I only do this for tiny joints and immediately wash my hands with clean running water. 


Right: I once again applied water to all surfaces and packed mortar all around the opening. This will hold the door in place.

Left: The opening with mortar, ready to receive the door.


Right: I immediately pressed the door in place. It took a little effort because the mortar created some friction. After setting it there was about 1/16’’ gap between the flange and the wall. The door actually sat that way for 35 years so I decided not to correct this small issue.

Left: Details of the bottom of the door: I troweled the mortar smooth and made sure there was a little bevel leading to the inside. This will avoid breaking the edge of the mortar when cleaning the pit.


Right: At the top, I  filled the minor gap between the flange and bricks with mortar. I also smoothed the joint as explained before. The only thing left now is to close the door and wait for the mortar to cure.

What an Improvement! It is difficult for me to cost this repair. I already had all materials and tools required with the exception of the black can of spray paint. It costed me $4.99 at a local hardware store and I only used half of the can.

Tools Used:

  • Brick Hammer
  • Pry Bar
  • Margin Trowel, Brick joint trowel.
  • Water Sprayer
  • Power Sander
  • Respirator
  • Spray Can Handle
  • 1 Gal bucket

Materials Used:

  • About half a can of “Loctite Extend Rust Neutralizer” 
  • About half a can of Rust-Oleum Exterior Black Spray Paint 
  • 80 Grit / 400 Grit Sand Paper 
  • About 2 lb of “SAKRETE – Type S High Strength Mortar Mix”

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