Tuesday, April 9, 2013

Brick Piers and Uneven Floors

     As we're taking up old flooring to check on joists and replace subflooring, it became very obvious that our brick piers in the crawl space are in need of some repairs. The mortar needs to be repointed, and, in some cases, the bricks were completely loose. I had no prior masonry experience, so I did a little research and got some advice from a coworker (thanks, Travis!) before jumping into this - hopefully this is helpful to someone :)

Several bricks off the top here were totally loose!
     Before the mid/late-nineteenth century, mortar primarily consisted of lime putty and sand. This formula cured very slowly, preventing bricklayers from setting more than seven courses per day. The advent of portland cement (patented in Great Britain in 1824; first produced in the U.S. in 1872) allowed masons to work much more quickly as it is a fast-curing cement. It can even cure under water! Until ca. 1900, portland cement was generally used as a minor additive to the classic lime putty/sand mortar recipe in order to speed up the curing time. The proportion of portland cement continued to increase, and by the 1930s most masons were using a 1:1 ratio of portland cement to lime putty (plus sand). The 1930s also saw changes in the production of both bricks and mortar as both became harder, more rigid
     Of course, you can have samples of your historic brick and mortar analyzed so that a custom-blended, color-matched mortar can be made... But this isn't exactly in our budget, and aesthetics aren't a huge concern in this case since the brick piers are under the house. My main concern was choosing a mortar that wasn't too rigid for our bricks. I learned that bricks expand and contract with fluctuations in moisture/temperature; thus, if the mortar surrounding the brick is too rigid, the brick could crack and lead to structural integrity issues. Based on recommendations from the National Park Service and This Old House, we went with a Type N mortar. This was available as a bagged pre-mix from Lowe's, but I did have to add the sand (mortar mix to sand was 1:3).

For your reading/viewing pleasure on repointing:

Mack, Robert C., and John P. Speweik
  1998  Repointing Mortar Joints in Historic Masonry Buildings. National Park Service Preservation Brief 2. U.S. Department of the Interior, Washington, D.C. http://www.nps.gov/hps/tps/briefs/brief02.htm.

[In case you're not familiar with these, the National Park Service has a series of preservation briefs on all topics from energy efficiency and HVAC systems to slate roofs and interior paint - good stuff! Here's the whole list of NPS briefs.]

Rist, Curtis
  2010  Repointing Brick. This Old House. http://www.thisoldhouse.com/toh/article/0,,232787,00.html?comment_page=1&comment_sort=ASC#toh-comments.

And a video tutorial by Tom Silva from This Old House (season 5, episode 24).

     Masonry is something I've always wanted to try, so I enjoyed doing the repointing. BUT there are several more brick piers to repoint in the tight, dark crawlspace - so ask me later if I enjoyed repointing those, haha! In other news, it was a pretty productive weekend. We finally got around to installing our new post and mailbox - it was our Valentine's Day present to each other :) Our plumber came to cap off the old kitchen sink vent pipe, and Steven patched the roof from the vent hole. However, a pretty awful discovery was made [@#$% ^&*!!!] as we were preparing to install floor joists in the recently enclosed former porch: the floor spanning the future kitchen/dining area is not level, not even close! The exterior wall we just added is level with what's on either side of it, so we're guessing this unlevel-ness happened from settling and additions to the house over time. We have a plan for installing the French door on the new wall, and we're making progress with installing the new joists.

If you've dealt with uneven floors across the span of a whole house, we'll take some good advice!