Brick repointing for 1960's era garage 1

[JAE]

I know that with old brick, the key to repointing is to sample the mortar and get its properties/proportions so that a good match can be made.

We have a 1960's era garage that has some exterior brick veneer that requires repairs - mostly replaced brick, repairs to cracks, cleaning and some repointing.

For the repointing, the client probably doesn't have the time or money to get samples sent out (there's not that much repointing).

Would it make sense to specify a Type N mortar (as opposed to the harder M or S mortars)? I'm reluctant to go softer (type O) as this is from the 1960's and I don't think
brick was that soft back then.

Any thoughts?

(just doing my part here, brimstoner!)

 

[SLTA]

Type N is probably safe on a 1960s garage. Be sure to use the right color sand to make it blend.

 

[Ron]

JAE...I agree with slta. Chances are the mortar will be relatively weak anyway. Sometimes masonry contractors doing repointing want to use a polymer additive similar to that used with tile grout. Avoid this as it will actually make the mortar stronger.

Also, if you can get a brick from an inconspicuous location, break it open and see if it was "crust fired" or fully fired. The difference will be softness on the interior (and even some friability) as compared to the outer face. While there will almost always be some differences, if the brick was fired too quickly or not at the right temperature, there will be a marked difference in the surface vs. interior hardness. This can help you with the mortar selection.

 

[dik]

Type N mortar will give you the 'softness' and 'plasticity/ductility' for a single storey structure. Minimise the amount of masonry cement, but still provide the proper hydraulic properties. It is likely too costly to undertake a petrographic study of the existing mortar and not much to be gained.

Dik

 

[concretemasonry]

The ASTM standards for mortar (appendix note 1) recommend to use the lowest strength mortar possible to carry the structural loads. For a veneer the dead load of the veneer is usually negligible, so Type N would be adequate structurally and provide many other valuable properties. The measurement of in situ strength is difficult and the results, if you can find a standard for comparison are really meaningless.

If you use a local sand and a type N mortar cement would be the best solution. For 1960, it is unlikely that a pre-proportioned or manufactured cement was used (or available) at that time. Some purists would push for a Type N mortar based on the proportions (not properties since they cannot be used at the same time) set forth in the ASTM C270, which does not even contain strength requirements.

For tuck pointing, the critical item is appearance is within a few days and not until the mortar has fully cured, but the excess moisture has been absorbed. - It is not worth construction a sample panel(LOL).

Dick

Engineer and international traveler interested in construction techniques, problems and proper design.