Waterproofing
Jimmy2007
| Posted in GBA Pro Help on
What is the best system to waterproof new concrete block and old concrete block?
Is parging with sand and cement and then covering with tar a good system to waterproof concrete block?
Parging with sand and cement to waterproof concrete block — also is it good to add ironite to that mix? Is it good to cover it with tar?
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Replies
Jimmy,
You posted this question three times -- which is confusing. I have consolidated your three posts into one post, so that your questions all appear on a single page.
"Waterproofing" has many meanings. In general, I think it's safe to say that if the hydrostatic pressure on the exterior of a concrete block wall is great enough, no system of parging or asphalt will keep water out.
To give you advice, we need to know more. The most important question is: Are you talking about a below-grade wall (a foundation wall that is part of a basement or crawlspace) or an above-grade wall?
If it is an above-grade wall, do you intend to have any siding or cladding?
It is a below-grade wall (basement). Thank you.
Jimmy,
Will you be working from the exterior (after excavating down to the footings), or will you be working from the interior?
From the exterior
Jimmy,
If you are working from the exterior, the two most important things you can do are:
1. Ensure that your foundation has a functioning footing drain leading to daylight, to a drywell, or to a sump equipped with a sump pump.
2. Install dimple mat.
Of course, a layer of asphaltic dampproofing on the exterior of your foundation wall never hurts.
For more information, see this article: "Using a Dimple Mat to Keep a Basement Wall Dry."
You should probably also read this article: "Fixing a Wet Basement."
I know that your recommendation is to install dimple mat, and I thank you for that information. That is the way I would like to do it but it seems very expensive. Someone is proposing to waterproof my below grade walls with this method: plaster, thoro-seal and tar basement walls, and install 1" insulation boards. Do you think this would work and be good for many years? Or how long do you think this system would last? Thank you again.
Jimmy,
The rigid insulation is, of course, a good idea. How thick the insulation should be depends on your climate zone. One inch of rigid insulation has an R-value of R-4 or R-5, depending on what type of rigid foam you are talking about. That would work in Climate Zone 3, but if you live in a colder climate zone, you'll need more insulation if you want to comply with most building codes.
In Climate Zone 4 (except Marine Zone 4), you''ll need a minimum of R-10 insulation.
In Climate Zones 5, 6, 7, 8, and Marine Zone 4, you'll need a minimum of R-15 insulation.
If this were my house, I wouldn't skip the footing drain and the dimple mat. Think of it this way: Most of the cost is getting a backhoe to do the excavation work and expose the exterior of the wall. Once you've made the big investment of excavating, you want to do everything right. Don't be tempted to cut corners and skip the dimple mat.
That makes a lot of sense, thank you so much again and I will follow your advise.
Thank you very much for all the help and information, I will read those articles. Have a great day!