Well–it’s been a long time since I posted anything (At that time my name was JohnD).
A question, because I have gotten really bad and conflicting advice from people who don’t know anything–like at H* D and L**.
What sort of mortar should you use when building/repairing cement block intended for below-grade use?
Oh, yes–I searched this site and there doesn’t seem to be any discussion on this topic.
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Replies
You can use an ordinary mortar mix; I usually use "Spec-mix" which has a bit more lime in it and, I've been led to believe, there is a little more Q/C in the mixing....same as above ground. When I use the premixed mortar in a bag, I usually richen it up a bit with Portland cement....like maybe no more than a coffee can or shovel full per bag.
mortar, mortar, doesnt matter.
You doing this with permits/inspection or just doing it?
What code applies where you are?
"Let's get crack-a-lackin" --- Adam Carolla
Well, it is really a repair job where an overenthusiastic backhoe caused a little damage and before they backfill, I want to do a decent repair job.
Where I am, code requires type M or type S for your application.
Couple simple recipes are:
Type M: 1 part masonry cement, between 2.25 and 3 parts sand.
Type S: 1 part portland, 1/2 part lime, 3.5 to 4.5 parts sand.
"Let's get crack-a-lackin" --- Adam Carolla
<a href="">http://www.taunton.com/finehomebuilding/pages/h00032.asp</a>
That should give you what you need. Note that it gives the mixtures- you'll most commonly find type N or S in stores, but you can add some p-cement to richen it up and get the strength and set you need.
zak
Hey Zak--that link doesn't work. Can you check it, or perhaps just give me some of the keywords and I will search the site myself. But thanks for the help.
http://www.taunton.com/finehomebuilding/pages/h00032.asp
There it is again, it looks like it'll work this time. Type M is your best bet, but if you can only find type S or N, just richen it up with some portland cement. or mix your own from scratch.
zak
Type S is what I use for repair work below grade such as gouges and and parge
coatings or anything that requires buildup coats. The more portland the mortar has in
the less it adheres to the surface you are trying to repair, but you also need enough
strength in the repair mortar to make it last type S is sticky plus enough portland to make iy strong.