OK, so I've never worked with brick and mortar before, but I get the basic concept. It might be sloppy for my first time, but Im sure i can build the basic three walls. (this is for an outdoor patio enclosure by the way...).

What I don't get is how to do the top part of the fireplace??? How do you get the bricks to stay put while the mortar drys? Can I just put a piece of sheet metal on my three fireplace walls and then brick over that? Whats the trick for making a hole for the metal pipe/vent? Is there a rule of thumb as to how large in diameter the vent pipe should be according to the area of the fireplace base?

Thanks!!

 

I assume you are referring to the brick that is laid over the opening. Usually a steel lintel is placed over that opening and the brick are laid on top of the lintel. It's also possible to build an arch negating the need for the steel lintel.

You are aware that special fire brick are needed in the fire box along with a fire rated mortar, right?

 

There was a thread a year or so ago about an outside fireplace that would not draw the smoke up the chimney. His problem was a flat top. A proper fireplace needs a cone shape above the fire that will fill with warm lighter air and establish a lighter column down through the chimney as opposed to the weight of air surrounding the fireplace. Not fun having to deal with a face full of smoke all the time.

Bud

 

Building something as complex as a fireplace is not recommended for a rank amateur. Proper performance and smoke draw depend on using the correct design for everything, including the smoke chamber and chimney, and is a lot more complex than just slopping a bunch of bricks and mortar together. If this is your first brick/mortar project, I suggest building something simpler first, like a planter, before getting into the intricacies of fireplaces.

 

How enclosed is this outdoor enclosure? You may want to consult an expert.

I have a grill in my house and one in my pool house type structure.

I can't use the one in the pool house because of poor chimney design. Period. This summer I'm installing an extractor because thats the only way I'll ever be able to use it. The one in my house on the other hand works like a charm, 100% natural convection and FAR more effective at pulling smoke, grease and cooking odors than my powered range hood.

The key is this shelf, the shape and size.

An angled chimney cap as well works as a Venturi pulling exhaust out.