Which side are you on: old school lime mortar or modern Type S? My wall blew out.

I'm working on a 1920s brick retaining wall over in Portland that started bulging after heavy rain. The old mortar was basically dust, so I figured I'd repoint with Type S to make it strong. But my buddy who does historic restorations said that's exactly wrong - he claims the hard mortar traps moisture and blows out the soft old bricks. I used Type S on half the wall and it's holding fine so far, but the homeowner wants the other half done in lime putty. Has anyone else run into this argument on older jobs? Which mix ended up lasting on your projects?

3 comments

3 Comments

felixfisher1mo ago

I did a 1910s foundation in Seattle last year and learned this one the hard way. Used Type S on one section and had spalling on the bricks within 18 months. The lime putty half still looks perfect after two winters.

margaret_kelly5528d ago

Stick with the lime putty mix for any Seattle job hands down. I've been patching up a 1908 craftsman in Capitol Hill for years and the Type N repairs I did back in 2018 are already cracking while the lime stuff from 2020 is still solid. Make sure you get a good hydraulic lime though, not just straight putty, or it won't set right in our damp springs.

the_ray1mo ago

Seattle's wet climate changes everything though. Type S has a lot more cement in it which makes it harder but also way less breathable. Those old soft bricks need to dry out or they'll trap moisture and blow apart from freeze thaw. The lime putty mix lets the whole assembly breathe like it was designed to. I've seen this pattern too many times on jobs up and down the coast. Modern mortars just dont play nice with historic brickwork in our kind of weather.