Repoiinting Firebrink

[jaygreg]

It's in the 30's today in Northern Ohio and I want to repoint the mortar at the top of my firebox (natural fireplace) where the damper frame meets the fire brick. My concern is the temperature; it's pretty cold inside there. I made a strofoam air block that works like a charm so the hearth isn't really exposed to the room air. The fireplace is also below ground level so that first three feet of dirt outside which is probably colder than hell is right against my fireplace chimney transferring that cold to the firebrick and into the hearth. Will this type of weather affect the ability of the mortar to set up properly?

[RicodJour]

As long as it doesn't get below freezing for the first week or so you'll be fine. If there's some doubt, stick an electric space heater in the fireplace.

First fire is a low and slow one so you don't cook the mortar.

R

[jaygreg]

[RicodJour]

You're welcome.

You know that buried masonry is a huge heat sink. It probably wouldn't be too difficult (at least for me!) to partially insulate the exterior of the chimney. Buried rigid insulation, either extending down vertically or extending out horizontally, would help. Something like this:

R

[jaygreg]

Got it. I had to dig that area up for a water problem a numbe of years ago and fortunately did put styrofoam on the bricks below grade. At the time, I thought I was protecting the tar coating from earth and rocks more than insulating it. Somethings we just luck out. :-)

I finished my tuck pointing and immediatley reduced the cold temperature in that hearth. It seams the cement around the damper assembly deteriorated (from heat and probably water that attacked it over the years) and was letting cold air stream in. I replaced the top 3 - 4 feet of the chimney two years ago and sprayed the bricks with a water repelant made for the purpose. I still get a little water dripping down the inside of the chimney but I think most of that is from rain that gets blown into the chimney. Nothing nearly like I used to get. I'll examine the joints agin next Spring. Some were tuck pointed with a silocone base cement compound made for brinks.

Thanks for the help.

[PeterD]

bricks below grade? Ouch.

[jaygreg]

[PeterD]

One factor is where you are located. Do you have frost and freezing weather?

[jaygreg]

Yep! Northern Ohio.

[PeterD]

Consider that brick is usually very porus, and repeated freeze/thaw cycles will not be healthy. Also brick is usually so rough that frost will tend to do a lot of pushing on it too.

Around here (Northern New England) you'd see cement to above grade for these reasons.

The above assumes that the brick is not plastered on the outside, however. That would help...