Right Mortar Type for Old Bricks


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Old 09-10-05, 08:45 AM
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Right Mortar Type for Old Bricks

I recently bought a brick house built in the 1880s with the older "hand molded" bricks. Several of the arches above the windows had collapsed, as well as several rows of bricks above the arches on the house's facade. Repairs had been made to these arches in the past using concrete which my mason said was a big "no no". He rebuilt the arches and adjoining bricks using Type S mortar. He additionally removed the concrete from other areas near these windows and repointed ... again using Type S mortar. The house had another related problem in that there was no capping over the exterior parapet wall causing water seepage problem in that wall. (This is an "end" rowhouse.) My roofer said the parapet wall would have to be repaired before he could put the copper capping on. So, on the instructions of the roofer, I had the mason rebuild the top 3 layers of bricks on that wall ... using the original bricks. Again, he used Type S mortar. Now, a neighbor tells me that because of the age of the bricks only the weaker Type H or O mortar should have been used and that I can expect to have brick breakage in the years to come. Is he right? Is there anything I can do now to rectify the situation other than requesting the mason redo the entire job ... which is unlikely to happen. The mason came well recommended by the roofer who has a long established business and the job was, frankly, very expensive. ($5,200 alone for correcting the facade problems around the three arches.) All the neighbors have commented on "what a good job" the mason did in restoring the facade. Is this just a temporary improvement? Thanks.
 
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Old 09-10-05, 12:03 PM
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Right Mortar Type for Old Bricks

The Type N mortar was probably not the type of mortar that was used in the original construction and is not what is usually used. It is stronger, but lacks the desired elasticity of the more desireable weaker mortars.

The modern "stronger is better" philosophy is not applicable to masonry repair or tuckpointing.

Type O mortar would have been the traditional desired choice. Type O may possibly be dropped from the current ASTM mortar specifications because the specification is aimed at structural masonry. Although your masonry is holding something up, it probably is really not "structural".

Of the readily available mortars, the Type N would be a better choice. It is more workable.

Just because the brick were "hand molded" does not mean they are weak. Since they have survived 125 years, I would consider them strong enough and durable.

It is doubtful that the mortar will cause the brick to crack since mortar shrinks over time. The brick do expand with time, but your brick are done doing that by now. If you have any problems, they probably would be minor joint cracks due to lower elasticity and lower bond to the brick.

Type S mortar is more difficult to work with, so if your mason did a good job with tight, well compacted joints your project should be satisfactory due to the workmanship. At least your mason did not use the strongest mortar (Type M). An unskilled or DIY mason would have had a problem with Type S mortar. The durability of masonry is due to workmanship and the fact that it is a very forgiving material in the big picture.

I hope this explains the confusion.

Dick
 
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Old 09-10-05, 01:56 PM
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thanks

Thanks Dick! It sounds like I can be confident that overall, the mason knew what he was doing, and that good workmanship can overcome any shortfalls from using the less than ideal mortar type.

Lance
 
 

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