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A Miracle in Silica and Water

Yesterday we met a sage of vintage masonry. After an extensive parade of contractors came by with contradictory advice on how to repair our chimney and front porch, Andy settled the debate. Within five minutes of arriving, we were up on the roof. Five minutes later his grinder was out and he'd removed the mortar one inch deep over a two square foot area. What did we discover?

• The chimney had actually already been rebuilt, just with the wrong type of mortar.
  
• The existing job was done using a cement mortar with little to no lime, which is much too hard for use with old bricks from 1914.
  
• The existing chimney cap isn't keeping water out. This, combined with the hard mortar and soft bricks, is forcing moisture out through the bricks and causing the white efflorescence to form on the brick face. (This can create spalling and eventually ruin the bricks beyond repair.)
  
• The chimney cap covers over the decommissioned chimney vent. We'll need a new cap and two stainless steel liners (one for each flue) to install the gas stove we've had our eye on.
  

Sounds bad. Don't worry, it gets better....

Andy surprised us by coming by one afternoon and doing a sample area on our front steps (the left side). The combination of grinding out the mortar and gentle low-pressure washing off the efflorescence and paint was a huge difference! The photo doesn't actually do it justice, since new tinted mortar will get rid of the remaining white and leave a rich dark look to the vintage brick. (Jeannie, heritage research watchdog, wants to talk to him a little about the psi used for washing, the actual silica product and machinery, and protecting the face of the brick. While we prefer to reuse this brick, we don't want to accidentally have the hard exterior of the brick blasted off and leaving it unprotected from future dirt, soot and salt.)

After his tests, Andy suggests that our chimney and front steps don't need to be rebuilt at all. He's recommending a complete grinding out of all the mortar, a water and silicone washing, and tuckpointing with a more appropriate mortar to match the composition and tint of the existing brick.

This was more hopeful news since every previous contractor insisted that we'd have to rebuild the entire front steps, check walls, sidewalls and the chimney above the roofline. (Obvious fact of the day: that would cost more and not match the rest of the house at all.) The improvement from Andy's sample makes us optimistic that we'd be able to save the unique brick-laid steps hidden under that awful blue paint as well as not waste money on a solution that wouldn't "suit" the house.

We still need to talk through the details of the job before we give him the thumbs up to start, but we're much more optimistic that we were a few weeks ago. Some things are looking up.

Posted by aaron on June 1, 2004 at 7:56 AM (4)

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