Masonry on concrete columns – air gap or not?
Toyoland66
| Posted in Energy Efficiency and Durability on
New construction in zone 7/8.
We have several free standing concrete columns that support deck framing and porch roof framing which will have a full thickness traditional stone veneer installed on them. Should the stone on these columns be installed with brick ties, weep holes, and a 1″ +/- air gap, or grouted solid to the concrete?
We also have two concrete retaining walls that will receive the same stone veneer on the exposed side, the side of these walls that contacts the soil will be either damp proofed or water proofed, same question as above, air gap or grouted solid?
Thanks in advance.
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Replies
Chris,
If this is "full thickness traditional stone veneer" -- that is, natural stones that are thick enough to create a stone and mortar wall -- I vote for no air gap.
If these stones are a manufactured product that is relatively thin, you should follow the manufacturer's recommendations.
Any retaining wall needs to be backfilled with free-draining material (for example, crushed stone) and to include drainage to daylight through the retaining wall -- some type of pipes or drainage holes at the bottom of the wall.
Thanks Martin.
Yes, I am referring to natural stone approx 4-5" thickness +/-, not thin stone or cultured/ precast stone. For some reason I am having a tough time finding installation best practices and standard details, it seems that most everyone is using adhered masonry in lieu of cavity walls.
Do you see any issues with running this fully grouted stone to just below grade? My concern is with freeze thaw action popping the stones loose. Running to below grade and not having any exposed concrete would be preferable aesthetically.
Chris,
Back in the early 1980s, I built two 40-foot stone chimneys for my house, using stones I gathered myself. I also built 8'6" high basement walls out of stone and mortar. I agree that it's hard to find good guidance on traditional stone masonry. The skill is almost lost.
A stone-and-mortar wall can extend below grade -- that's a traditional approach to building a foundation. My basement walls haven't moved a bit in 36 years, nor have they suffered frost damage.
If you are mixing your own mortar, using sand, lime, and Portland cement (rather than using a mortar mix) -- and if you favor a traditional high lime mix for your above-grade work -- go easy on the lime and heavy on the Portland cement for the below-grade mortar. Good luck.
If I can ask a few additional related questions:
We will have a finished basement with the same stone on the exposed surfaces of the foundation walls, the stone will sit on a 6" deep brick ledge (12"-16" thick foundation wall incl. brickledge). Similar condition in that the stone will run below grade so no exposed concrete is seen on the foundation.
-Can we also fully grout this stone to the foundation with no air gap (I assume yes)
-What is your opinion on running the foundation waterproofing (bituthene type adhered membrane) over the top of the brickledge and up the concrete behind the stone
-If I did this, I could run the bituthene over the top of the foundation wall as well in lieu of using a sill gasket.
My reason for wanting to do this is that if the waterproofing terminates at the brick ledge there will be un-waterproofed foundation sitting below grade in the areas where the stone runs below grade.
Chris,
I understand your desire to run the peel-and-stick behind the stone. The only caveat is that you won't be able to depend on any bond between the mortar and the concrete wall -- so that your relatively thin (6 inch thick) stone-and-mortar wall needs to be self-supporting. As long as the wall isn't too high, that's certainly possible, as long as the mason is skilled and aware of the factors that make a stone-and-mortar wall strong from a structural perspective.
You don't want a tippy stone-and-mortar veneer that topples forward.