[whitestonehome]

I am adding a gas fireplace to an existing home. In order to save space inside, I am building a platform on the exterior of the home and framing with wood tall enough for the vent. The contractor poured the slab but did not finish with the concrete.

I want to build using blocks up to the home foundation, then frame with wood the rest.

Has anyone do this before. How do I ensure the where the existing home foundation and new block wall is stable and waterproof. Thank you

 

[Nealtw]

I am adding a gas fireplace to an existing home. In order to save space inside, I am building a platform on the exterior of the home and framing with wood tall enough for the vent. The contractor poured the slab but did not finish with the concrete.

I want to build using blocks up to the home foundation, then frame with wood the rest.

Has anyone do this before. How do I ensure the where the existing home foundation and new block wall is stable and waterproof. Thank you

We hang them off the house, How far off the ground are you?

 

[whitestonehome]

We hang them off the house, How far off the ground are you?

Its 5 feet from the footings to the top of the foundation. The platform will not be suspended in the air.

 

[Nealtw]

Its 5 feet from the footings to the top of the foundation. The platform will not be suspended in the air.

So your footing is tied to the house footing.

Sorry I no little or less about placing block but I think they do have ties you would put to the foundation.
Any thought about moisture caught inside it?

 

[mark sr]

While I've built several masonry chimneys for wood stoves, I've never dealt with gas fireplaces. Block is porous and won't be watertight without flashing along with covering the block with stucco or paint. Brick ties can be tap conned to the existing block.

 

[jomama45]

If you're worried about it filling up with water and leaking into the basment somehow (fairly unlikely IMO, unless you have a basement window under the new FP) tie into the existing exterior draintile to keep the new foundation drained.

As for tying into the house, we use 3/8"rebar dowels into the existing foundation at every other course. 3/8" is small enough that it requires very little chiselling to the bottom of the block. We also pour the cell closest to the existing wall full of grout and add a vertical rebar.