Concrete Foundation for grave headstone
Concrete Foundation for grave headstone
(OP)
Where can I find the requirements for concrete foundations for grave headstones in Ontario? Particularly I am interested in knowing where to find the minimum required depth. I am wondering if it is 1.2 m (4') as it is for building exterior foundations in this geographic area (Toronto). The question arises in relation to restoration of a number of 100 year old headstones in a cemetery in Toronto, that have fallen over or are leaning. I am told that these headstones were just stuck into the ground, with no concrete foundation. I have not found this information in the Ontario Cemetery act. I am a structural engineer and have been asked about this.






RE: Concrete Foundation for grave headstone
For small, individual headstones, in order of preference, I'd be inclined to:
1) Just set them right again and hope for the best.
2) Connect them to a shallow pad footing that is allowed to float with frost (frost depth in the field can be 7' here).
3) Connect them to a shallow pad footing at frost depth.
4) Connect them to a screw pile if there's access available.
For big things like statues and mausoleums, using shallow frost protected shallow foundations has proven economical.
One needs to keep in mind the nature of the facility. Too much open excavation and you risk setting a bunch of zombies free. Not cool.
I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.
RE: Concrete Foundation for grave headstone
Interesting question though when I think about the stone mausoleum that was recently constructed nearby (in Toronto) (much different than a grave stone, it is likely 300 sq.ft). I should have looked at it closer during construction but would assume it was a) engineered, b) perhaps permitted, c) had footings and frost walls supporting the stone structure.
RE: Concrete Foundation for grave headstone
RE: Concrete Foundation for grave headstone
RE: Concrete Foundation for grave headstone
http://www.bramm-uk.org/userfiles/documents/4/The%...
RE: Concrete Foundation for grave headstone
RE: Concrete Foundation for grave headstone
To Debyloco: Your attachment is very interesting indeed. A special thanks to you. It looks though like this is a British Standard, so I am not sure that they have as severe a number of freeze cycles as we do here in Toronto. Nevertheless it is interesting and useful.
ToOldBldguy: I am not sure why you say depth is not the issue. Perhaps you are located in an area that does not see freeze-thaw cycling, ice lensing and the like, which plays havoc with foundations in unheated areas of buildings (frost heave, etc.). Where generally are you located?
Further Information:
Normally in the Toronto area, foundations for new headstones would be founded at 1.2 m depth i.e depth of frost penetration in Toronto area. My question however relates to an existing relatively old cemetery. Many of the headstones are over 100 years old, and some did not have foundations that extended to 1.2 m. Many are leaning badly and some have toppled over. Some may perhaps even have been just stuck into the ground with no separate foundation. We (a charitable organization) are trying to restore a significant number of headstones without spending excessive amounts of money, if possible. There are seemingly no local standards so this is a bit of a geotechnical/structural question of how to do it economically, but still achieve a reasonable design life. One person on the committee wants to just set them on shallow foundation (same idea as Kootk put forward), but I wonder how long it will be until noticeable movement occurs (this would be done only for the 18" high essentially flat or slightly sloping headstones, not for the higher ones). The soil is a silty clay, so I expect it is vert susceptible to frost heave, etc.
RE: Concrete Foundation for grave headstone
What would happen if you auger drilled a couple 10-12" dia. holes, side by side, 1.2m deep and cleaned out a bit btwn. the two holes, would the soil stand on its own? Then, on top, at grade, use a simple form 16"x30"x9.25" deep for a cap, with a couple dowels in it, up into the bot. of the headstone; and fill the top form and holes in one shot of conc. Maybe fab. a couple different sized light stl. forms which are reusable, with lifting/pulling handles and dowel holders and all. These stl. forms could probably be driven down into the top soil, to proper top elev. and then cleaned out inside for pouring, but then, to also minimize cleanup (grass planting, etc.) work outside the form, when it’s removed. Finish a nice draining slope around the top of this cap to match the base size of the headstone, and grout the headstone in place.
RE: Concrete Foundation for grave headstone
Interesting Cemetery Conservation websites:
Link
Link
Link
RE: Concrete Foundation for grave headstone
Isaiah 28:16
RE: Concrete Foundation for grave headstone
I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.
RE: Concrete Foundation for grave headstone
RE: Concrete Foundation for grave headstone
RE: Concrete Foundation for grave headstone
To mijowe: When Isaiah says "stone of sure foundation", does he give any details of how to accomplish that? I am sure he was not thinking in terms of frost heave, so that may not be too useful even if he did give details, much as I admire Isaiah.
To OldBldgGuy: If nature was perfectly uniform and symmetrical, then you would be right, that it may not matter that much if the top of the base is higher in summer then winter. But since soil is not uniform, the frost heave is not uniform i.e. each corner of the base may lift a different amount than another corner, so it will end up not level. Also, it never settles down exactly into the position it started in. After just a few seasons, the lack of levelness due to frost action in the cohesive soil may not be particularly noticeable, but after a number of years it will be. By 25 years, it will likely be quite noticeable. I am sure you would agree with me that if you want a base that is designed to stay level for at least 25 years or more, and the soil is clay, then the foundation should extend down to 1.2 m (Toronto area frost depth) in accordance with good engineering and construction practice in the Toronto area. If you are prepared to rebuild the base every 10 to 25 years, then the 1.2 m depth may perhaps not be essential.
RE: Concrete Foundation for grave headstone
RE: Concrete Foundation for grave headstone
RE: Concrete Foundation for grave headstone
RE: Concrete Foundation for grave headstone
Perhaps you can help me to be better persuaded if you can tell me:
a) whether those well-performing examples that you site had a clay soil under the foundation?
b) whether the top of slab remained level after 25 years?
c) why the building Code requires 1.2 m of frost protection for building footings that are subject to frost action, if perfectly fine performance can be achieved without going down to the depth of frost penetration?
I realize that sidewalks are replaced for may reasons, not just that they have become unlevel.
Nevertheless, when walking, I frequently look down to see the date, and I find few sidewalks are more than 20 years old. Try it and see what you find. I'd be interested. I don't think the analogy with sidewalks is necessarily apt. No one is bothered by lack of levelness of a sidewalk. Lack of levelness of a support for a headstone is not quite the same thing, as I feel it is a lack of dignity to the departed, although I may be wrong in that opinion.
To Jayrod: a few years ago there was a case locally of a headstone toppling onto a child. I am not sure that I can agree that I am "putting way too much effort" into it. This is not just one or 2 headstones. There are about 30 headstones, so in my opinion it is worth putting some effort into it, as it may save significant costs and/or achieve a longer lasting restorations and reduce life cycle costs. I understand that you hold a different opinion, and I respect and value your advice. I like your suggestion of removing the top 1.2 m of soil and filling it with a non frost susceptible material, if this turns out to be more cost effective.
To epoxybot: I notice that I forgot to thank you for the links.. So let me thank you now. Much appreciated.
I'd be interested in hearing anyone else's opinion as well.
RE: Concrete Foundation for grave headstone
If it is a slender stone (few inches thick) then the typically dig ~12" wide x 18-24" deep, just to prevent leaning too much.
For larger stones they would make the footing 6" wider than the base of the monument x 24" + whatever they feel fits the height, taller ones they go deeper.
As has been said, no one really cares if they rise or settle a bit, it is resisting overturning that matters.
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P.E. Metallurgy, Plymouth Tube
RE: Concrete Foundation for grave headstone
RE: Concrete Foundation for grave headstone
Canuck65 - Would you happen to have a contact person at Mt. Pleasant Cemetery that I can contact who would be willing to talk to me about this?
Ed - do you know if the 2 foot deep foundations that you observed were on a granular soil, or a cohesive soil?
RE: Concrete Foundation for grave headstone
RE: Concrete Foundation for grave headstone
RE: Concrete Foundation for grave headstone
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P.E. Metallurgy, Plymouth Tube
RE: Concrete Foundation for grave headstone
RE: Concrete Foundation for grave headstone
Dad & I overlap, we can't take credit for the cumulative total of years. The Ontario & National building codes do not require 1.2m frost cover. That's a prescriptive number for soil used for Part 9 in place of engineering judgement and design (and it actually says 1.2m "unless local experience says it should be otherwise"). An engineer should be able to distinguish between when the prescriptive number is convenient, economical, or necessary; when a material other than soil is appropriate (insulation?); and when neither is necessary or appropriate. If one can't, that's fine, they can defer to someone who can. There are a multitude of configurations and circumstances, and appropriate design details for them. Clay, sand, gravel, peat, rock; they all require different considerations. That doesn't mean one has to default to the non-engineered approach. It might seem impossible but I have a 1500 sq.ft. unheated barn attached to a 700 sq.ft. heated workshop on a continuous reinforced concrete slab on grade. The barn sits on a 2' high 2-wythe kneewall of block & brick bearing a heavy timber structure, and the workshop is of typical stick framing sitting directly on the slab with a 2' high brick skirt to deflect splash from the roof. There's plumbing in the workshop. There isn't a crack in the masonry & nothing but shrinkage cracks in the slab, it's more than 20 years old (I dismantled & relocated the 175 yr. old barn), and it's founded on clay, but it's properly designed, drained, and insulated. I've designed and built countless heated & unheated structures on reinforced slabs including a 6000 sq ft church with 54' span scissor trusses and 100% masonry exterior cladding (built 2010, no drywall cracks in 2015), a 6000 sq.ft. unheated pre-engineered steel building for Ontario Hydro (25 years ago) and within the last 2 months 3 pre-engineered steel buildings >7500 sq.ft. both heated and unheated. I've also seen plenty of designs from other engineers for similar buildings (contractors love to shop), with very little deviation from what I would recommend. Just because one hasn't managed to do it oneself, it doesn't mean it can't be done.
RE: Concrete Foundation for grave headstone
Thank you for the very detailed and clear response. Your experience and information seems to prove the rule that I made up for myself some years ago, namely that the more certain that I am that I am right, the more likely it is that I am wrong! Well I came on this forum to learn, and you have been a good teacher. You have provided persuasive information that it does work, in clay soil, and that it has continued to work over a significantly long period of time. Thank you again for your counsel and patience. Much appreciated.
RE: Concrete Foundation for grave headstone
Just a bit of follow-up.
I notice that you say that it's insulated. Do you mean that it is insulated under the slab? If so, then I am not at all surprised that it has been successful. I have done that successfully too, and is not that uncommon to do so. However to put insulation under a headstone foundation would mean having to extend it about 1.2 m beyond the headstone foundation, all sides. It is something I had considered before posting the question, but that has some practical considerations. Also, it may not be that practical to put underslab drainage for a headstone foundation. Or is there no insulation under the slab in your unheated building?
RE: Concrete Foundation for grave headstone
RE: Concrete Foundation for grave headstone