Basement window replacement

Submitted by kevabar t3_z8d3nk in DIY

I have 4 wooden single pane windows that need replacing after 71 years. The wooden frame (red lines in photo) is encased in mortar in the corners and other parts. My new windows are 1/4 to 3/8 inches wider than the existing wood frame. My plan is to grind away some of the mortar with a grinder. Will thinning up the mortar (blue lines) on the sides cause any structural concerns at the end of the cinder block courses? What if the mortar on the sides cracks, chips, or crumbles? (Unfortunately to get smaller window, they would be significantly smaller.) https://imgur.com/a/7dlksuY

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SawdustMaker1 t1_iyb4kix wrote

I just completed the same job at my son's house. Don't go to the trouble of grinding out the mortar around the window frame. My guess is that it will chip away from the block quite easily once the window and jambs are removed. Chip away all of the old mortar surrounding the old windows and start fresh. Install your new windows level and plumb, then spray foam around them. Once the foam has set, repoint the space around the new windows with mortar, if you wish. I only did the outside, making sure to slope the mortar away for good water runoff.

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BooyaHBooya t1_iyb3n4j wrote

Not a pro, but I don't see an issue as long as you aren't grinding into the block.

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Omnicidal_Ungulate t1_iybaz70 wrote

1st not a pro. Semi pro with restoration experience. In my experience the mortar that you are talking about was added the the gap after the outer framing, in a poured foundation they would have put the uprights and sills in during the pour. remember in those days the carpenter would build the windows on site and to measure. The mortar usually is quite fragile and chips away easily. Likely to be adhered only well on the block side so care not to damage the block is needed. I would remove existing windows and mortar then install the new window as one would nowadays then use spay foam to fill void. Then cap with appropriate trim.

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