Sandstone Foundation

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Kashka-Kat
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Re: Sandstone Foundation

Post by Kashka-Kat »

OK, heres what they were going to do and what I can do myself. Its not rocket science! Perhaps pay a kid to do the digging instead of a professional guy

Dig down at least 18 inches below grade, repoint (they refused to tell me what theyd use but Im thinking either type M or K - what say you? Maybe it should be something harder/tougher on the exterior, even though its below grade?)

Also they were going to lay some sort of membrane (I dont know what, perhaps EPDM?) vertically against the exterior wall and then having it slope horizontally away from the house, and then refill with 18" of dirt sloping away from the house (actually it will be a raised bed so it might be more like 24")

Unfortunately there is a downspout in that corner so I may want to have it go into underground pipe instead and direct it farther away from the house. What would you use for this purpose? the cheap corrugated black plastic is useless- leaks. Would PVC be overkill?

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Lily left the valley
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Re: Sandstone Foundation

Post by Lily left the valley »

Kashka-Kat wrote:Also they were going to lay some sort of membrane (I dont know what, perhaps EPDM?) vertically against the exterior wall and then having it slope horizontally away from the house, and then refill with 18" of dirt sloping away from the house (actually it will be a raised bed so it might be more like 24")

Unfortunately there is a downspout in that corner so I may want to have it go into underground pipe instead and direct it farther away from the house. What would you use for this purpose? the cheap corrugated black plastic is useless- leaks. Would PVC be overkill?
Since we're also dealing with a regrade soon enough here, I can say that the height of the top of the slope is not what matters aside from the recommended no closer than 6" to the bottom of the siding. It's the angle degree. The 6" over 10 ft. you see mentioned below is a fairly standard noted number combo.
Image
Here's another that states the 2" per foot ratio. Here they have a barrier, but it's under the gradient rather than against the vertical surface. It is sort of tucked up against the wall a bit. I've seen different variations on how much against the wall that goes.
Image

You also want to space any beds so that mature plantings in them are not rooting up against the foundation in a pushy want to find a crack to open kind of way. Too close and it can also act as a bridge for bugs to get behind the siding above ground.
Image

Lastly, where the beds are concerned, don't do the half circle "mounds" where the ground heads back towards the foundation on the side closest to the house as well as in the front. That defeats the entire point of why you graded away from the house overall. (This is very common when landscapers come in to do plantings if they don't train their crews properly, especially in new house builds.)

No, I don't think PVC would be overkill, especially if you're running it underground.

Good luck with it, and I look forward to hearing how things go.
--Proud member of the Industrious Cheapskate Club
--Currently pondering ways to encourage thoughtful restovation and discourage mindless renovation.

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DRJR
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Re: Sandstone Foundation

Post by DRJR »

4"PVC drain pipe is what you want. Your big box hardware stores will have it in the plumbing section.
Home formally know as Rotten Ranch

Patched up fireplace, rotten and new siding, with other issues getting the arts and crafts makeover. :mrgreen:

Kashka-Kat
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Re: Sandstone Foundation

Post by Kashka-Kat »

Oh wow that 2nd diagram really helps. I think if I do it the way thats been suggested to me, the furring strip would simply go above, or at grade, with the membrane hanging down vertically, then perhaps a second furring strip about 18 inches down where the membrane then is laid outward away from the house at a slant. Wonder how far out from the house it needs to go?

Or do I even want that vertical portion at all. Dont I want vapor to be free to go in both directions both in and out of the basement? (IE moisture from laundry, etc. might get trapped???). Arghhh this is so confusing.

Next question. Interior of basement has some parging over the sandstone foundation - it appears to be original, or so I think because it is same color and texture as the mortar between the rocks. Unless the whole thing was mortared at a later date. Anyway rather than remove it I want to repair/fill in missing parging.

What the heck is parging anyway - is it just mortar applied over the walls? Do I assume that any soft mortar mix is going to work or should I get it tested to make sure.

Greenwood
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Re: Sandstone Foundation

Post by Greenwood »

Kashka-Kat, I had a long answer drafted and lost it. The short answer, as far as I can tell (and I'm no mason by any means), is that the mortar and parging protect the blocks by acting as a sacrifice to water and salts - see http://www.greenbuildingadvisor.com/blo ... ce-podcast
So, parging is simply something for water and salt to leach into, away from the stone or brick or block. You would want to use lime mortar and lime parging.
Andrea

Greenwood
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Re: Sandstone Foundation

Post by Greenwood »

Follow up - I am trying to sort out a recipe for mortar and parging. This is the clearest explanation I have found regarding the types of pre-mixed mortar available:
(https://stlbrickrepair.com/2014/03/10/m ... g-masonry/)

Type M — The strongest (Highest PSI @ 2500) of the group, this type is most commonly used for load bearing walls and below grade applications, such as foundations or retaining walls.  The Recipe: 3 parts Portland, 1 part lime and 12 parts sand. The low concentration of lime helps to achieve this high strength, but takes away from bonding ability. (A poor choice for tuckpointing anything.)

Type S — Also strong, @ 1800 PSI, Type S is most commonly used for laying.  The Recipe: 2 parts Portland, 1 part lime and 9 parts sand. Because of it’s increased amount of lime, it offers the most flexibility in use and resistance to movement and weather.

Type N — A common mix for tuckpointing, and laying softer materials, Type N is the most flexible and resilient @ 750 PSI. The recipe: 1 part Portland, 1 part lime and 6 parts sand. Furthering the concentration of lime in the mix does take away from the structural strength aspects, but in turn offers more resilience and flexibility. Perfect for tuckpointing most exterior walls and chimneys.

Type O — At 350 PSI, this is the lowest strength mortar available in pre-mix. With the lots or lime, The recipe is: 1 part Portland, 2 parts lime and 9 parts sand. Not often used outdoors, Type O’s uses are limited to non load bearing walls and is generally an interior only used mix.

Type K — Abandoned for most practical uses, before I entered the trade, Type K is the least seen or used. Type K mortar is generally used only for interior or historical pointing of soft, hand-made brick. I’ve only made it once for curiosity’s sake only. (It’s a sticky mess.) Type K mortar has the lowest compressive strength @ 75 PSI.,  
The recipe:  1 part Portland, 3 parts lime, and 10 parts sand. The increased porosity of this mortar can help protect movement of material it surrounds.

Lime Mortar/Type L — Not really a type or mortar or a mortar alone by means of the definition of the word (mortar). Type L is a mix, of only, lime and sand, NO CEMENT. The Recipe: Varying amounts of Lime & Varying amounts of sand. It’s not commonly worked with and is generally only used for Historical tuckpointing purposes.


I've read somewhere that a recipe for historic homes is 1 part Portland cement, 4 parts lime, and 9 parts sand. None of those pre-mixtures fit this ratio.

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Lily left the valley
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Re: Sandstone Foundation

Post by Lily left the valley »

Greenwood wrote:Follow up - I am trying to sort out a recipe for mortar and parging. This is the clearest explanation I have found regarding the types of pre-mixed mortar available:{snip}
Great info to have. Thank you for sharing this. :thumbup:
--Proud member of the Industrious Cheapskate Club
--Currently pondering ways to encourage thoughtful restovation and discourage mindless renovation.

Kashka-Kat
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Re: Sandstone Foundation

Post by Kashka-Kat »

Oh wow - this old thread. Interesting to read and remember all the twists and turns of figuring out how to do this.

The whole Portland+lime+sand approach proved to be not really easy to figure out cos the bagged cements around here all have their proporietary ingredients which they wont tell you about - some apparently don't even have any lime at all. Yeah you can buy the separate ingredients and mix, but then there was such a bewildering array of recipes - types of lime to consider etc. - I got stalled.

In the meantime, the ever helpful Limeworks folks as well as some historic masonry supply folks in Chicago (Henry Frerk and sons) recommended natural hydraulic lime (not hydrated). Also known as NHL. Its always reassuring when I hear two separate sources recommend same thing. And as I finally got to work I saw that that's exactly what had been used originally, both for the pointing and for the parging on the interior basement wall. This type of sandstone rubble foundation actually is supposed to have a thick finishing coat on the outside so the surface is made flat. Otherwise youd have dips and dents where water gets trapped. Quite ok to do if its a breathable substance like NHL. I find it enjoyable to work with - its kinda like mixing pie dough, although more crumbly. It actually has some benefits - breathable, self healing. Down side is it takes forever and a day to cure, and if it does get torrentially soaked over a long period of time it does break back down into its components, lime and sand.. But I will be doing the other steps to prevent that from happening again.

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