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Replacing Leaky Rotted Basement Windows – Part 3 of 3

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This post is Part 3 of the Replacing Leaky Rotted Basement Windows article.  If you missed Part 1 of 3, click here.  For Part 2 of 3, click here

DETAILED INSTRUCTIONS

STEP 3 – REMOVING CONCRETE / MORTAR

As expected, this is the most time consuming, physically challenging part of this project.  Although slinging a 3 pound mash hammer feels easy at first, try swinging it hundreds of times in a confined space and you can appreciate hard manual labor!

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As seen in above pictures, I need to remove quite a bit of mortar from the bottom sill.  I intended to leave the side sills intact as much as possible because I had no reason to remove them.  Before getting started, make sure to wear your safety goggle at all times, as well as some type of ear protection.

I decided against renting a power tool because I was concerned of peripheral damage to the foundation cinder blocks.  Rather than creating more repair work, I reasoned that it would be more time efficient to manually chip away the mortar.  As previously stated, my main tools were 3 pound mash hammer and a couple of cold chisel with point and spade tips.

Before starting, I examined the bottom mortar sill for any cracks as a starting point.  Switching between pointed and spade tips, it took about 1.5 hours to complete.

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STEP 4 – DRY / TEST FITTING WINDOW

Whew. That was some hard work! Now before we get all excited, let’s dry fit the window.  Please note that I had to go through several iterations of chipping off high points to get the window to fit into the opening.  As always, please take your time and try to chip off little at a time.

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STEP 5 – CLEAN SURFACE

Perfect fit. I am not too concerned about small gaps on the bottom as they will be sealed by an expanding window foam. But for now, grab yourself a can of compressed air or if you have one handy, turn on the compressor and clean off the dust. You want a good solid bonding between caulking/foam against all surfaces so take your time and clear off any small debris /dust from the surface.

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STEP 6 – CAULKING THE WINDOW

First of all, I used a clear caulk because it gave me most flexibility in terms of it blending it with the surrounding color. Although the caulk is white when first squeezed out, when it dried it became clear. Also, I planned on attaching the window frame to the bottom of the sill plate so I DID NOT caulk the bottom of the window. However, I laid down 2 separate caulking tracks on the top part of the window as well as caulk line on the bottom of the sill to ensure a solid seal against draft.

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STEP 7 – SEALING THE WINDOW WITH EXPANDING FOAM

There are numerous types of foam sealants out on the market. You need to make sure to purchase one that is specifically made for windows and doors because foam sealants can be powerful enough to warp or bend window or door frames.
I no longer recommend Dow Chemical’s Great Stuff for Windows and Doors because they use a dispensing system that is highly unreliable. Just for this project, I had purchased 2 cans per window (total of 8 cans for 4 basement windows)  and 5 cans did not dispense! In addition, Dow Chemical’s dispensing system is made such that it is virtually impossible to re-use half-full cans. Instead, I recommend using Dap Tex Plus 18836 Window and Door Foam Sealant 12-Ounce cans.  It costs around $1.25 extra but its dispensing system is reliable so it will be more economical in the long run.  If you purchase through Amazon, make sure to buy extra for future projects to save on shipping cost.

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STEP 8 – FINISHING TOUCHES

For the sake of image clarity, I had to use pictures from 2 basement windows

Alright, we are almost to the finish line. After couple of days, liquid foam has turned hard so it was easy to cut off the excess. Any sharp utility knife will do but if you don’t already own one, get Stanley 10-989 Contractor Grade Swivel-Lock Retractable Utility Knife. This knife has a gentle curve that save your knuckles from being shredded by a hard concrete surface! Once the foam has been cut, take a 6 inch drywall taping knife and scrape off the excess. There are so many uses for this taping knife so dedicate one for use around the house. Any kind will do like MARSHALLTOWN The Premier Line M5763 6-Inch Flex Joint Knife with EMPACT Handle but avoid buying plastic ones as the blades will not survive being scraped on a hard surface.

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To repair the damage, I needed a bag of mortar mix. Because this was my last window, I decided to purchase a small, ready mix bag from a local big box store. I don’t recommend buying this online due to shipping cost though Sika Corp. 05MG060 Sika Mix & Go

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When mixing mortar, ALWAYS add less water than the stated amount. You can always add more water later; if you have too much water, the only way to fix it is to have more dry mortar to mix in. As far as the consistency is concerned, think about a peanut butter jar that has been sitting out. Very easy to spread, but not drippy. If you have a large chunk to repair, you will need to do it over the course of several days by adding a layer each time. If you were to place a large amount of wet mortar in one place, it will most likely droop as well as form a crack. The pictures I have is from my coating and you can see the depression on the left side of the window. I will be revisiting the window when the weather gets little bit warmer to add a final coat.

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Well, that’s it. If you found this article to be helpful, please click on one of the social icons to share it with your family and friends. Also, don’t forget to subscribe to receive free project updates and be entered into a weekly drawing for free 10% Lowes coupon.

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Comments

  1. Many thanks for taking the time to post both text words and supporting pictures. And, for posting your many great supporting tips as well. You do great work! And, your posted info will save me hundreds of dollars in the future – when I replace the old / leaky 4 x basement windows in my cottage. Thank you!

  2. thanks jack! nothing beats that awesome feeling when you get your diy project done the right way!

  3. My house is masonry with wood trim on the outside.
    I would like to install the window from the inside and leave the wood trim in tack.
    Please advise.

  4. @Mary Ann-

    If it is a basement window, all you have to do is take the interior measurement from left side jamb to right side jamb (plus top and bottom sills).

    Although the glass area will be reduced somewhat, it’s pretty much a drop in (like installing a replacement window) without disturbing the wood frame.

    Please read Sections 1 and 2 to read about taking measurements.

  5. Unless I missed it, you didn’t use anything but the expanding foam to attach the window to the house. Is that all that’s needed? I’m asking because I’m about to replace two basement windows also. Thanks.

  6. @Ian-

    Yes, in my case, I decided to use foam because of three reasons:

    1. One basement window is under the newly installed deck and thus it is not accessible;
    2. The other window faces 4 neighboring houses;
    3. I wanted maximum light into the basement.

    However, there are drawbacks:
    1. Foam-only is obviously not as secure as attaching to a wood frame;
    2. It takes time to chisel and even out the concrete opening;
    3. Depending on how the condition of your brick exterior, you may need to patch it up (like I explained in the article).

    If your window wood frame is in good condition (i.e. not rotted), I would keep it and just replace the window.

    Hope this helps?

    Kevin
    would be more secure, but I felt that it

  7. Just for future readers that come across this…this is NOT a good way of doing this window install. All the spray foam and nothing else (except for the top) is no good. It is equally as easy, and better, to simply fill the gaps around the new window with mortar. You can lock the new window in place with mortar easily and still not use any wood. Install and level the window as shown here with screws through the top and some caulking. Then pack mortar all around the window frame. That’s it. If you want a better “bite” for the connection of the window to the mortar around it, you can install screws into the outside of the new window all around its outside edge. Just don’t screw too far in that it comes through the inside of the window frame. What you are left with are screw heads sticking out all around the outside edge of the window frame. How far they stick out is up to you. Generally 1/2″ to 3/4″ is fine. Depends how much room you have between the new window frame and the window opening. Then squish in mortar all around the window frame and all around the screws. Fill it up all the way around. Then finish the mortar as you want. Slope the sill if you want. With the mortar, repair any damage you made. Done. Very easy. No wood to rot out. And no ridiculously ugly and messy spray foam to seal anything up with.

    Also, an angle grinder with stone cutting wheel or grinding wheel would have made your demo wayyyyyyyy easier and actually would be way cleaner and less likely of causing damage than chisels and hammers. If you use the right power tools it is way faster and more controlled.

  8. @craig-

    Thanks for your comment. I do have some follow up questions:

    1. When you pack the surrounding gap with mortar, how do you make sure it does not ooze out? Wouldn’t you have to set up some sort of a form to prevent that from happening?

    2. I did consider the power tool but it would have generated way too much dust Do you have any special power tools that you know if that can control dust?

  9. @Craig — Thanks for the info about the mortar. I have steel frame windows embedded in concrete so patching up with mortar seems like a good way to make it look nice. I’m not quite there yet. My plywood window has some nice character to it 🙂

    I have to second the recommendation on using power tools. I rented a hammer-drill and it was awesome for chipping away the concrete that was used as a bed underneath the old, very difficult to remove frame. I had to use a large pry-bar. Generally I did a little more damage than I would have liked, but I’m not sure how I would have gotten those beasts out otherwise. Way it goes I guess.

    I felt like the hammer-drill really didn’t make much more of a mess than a manual masonry chisel would have and it save me a LOT of time and grief – I got all the cement chipped out and a hole drilled for a bathroom fan before my 4 hour rental period was up! It was messy though I’m not sure how you get around that.

    FWIW chipping out the concrete with the hammer drill makes less mess than the grinder, but the grinder gives a much better edge. Trade-offs I guess.

    I was only somewhat successful at sealing off the dust 🙂

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