Concrete Foundation for grave headstone 3

[ajk1]

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.

 

[Canuck65]

If you would like to look into how things are typically done in Toronto, I would suggest you contact Mt. Pleasant Cemetery. I say this only because a few years ago I was brought in to provide an engineering opinion on a grave stone (not the foundation, only the gravestone) for a family and Mt. Pleasant was responding with a) their written standards and drawings, and b) their engineers opinion. I think there is likely a wealth of information that you may obtain from a large operation such as Mt. Pleasant.

 

[ajk1]

ok, thanks. Much appreciated.

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?

 

[Canuck65]

I do not have a specific contact person, I was working through a memorial stone company who were the main point of contact and all the info I was provided was heavily censored as it was for a very high profile, confidential, 6 figure $$ gravesite.

 

[ajk1]

to Canuck65 - ok, I understand.

 

[EdStainless]

Many places in WI you are digging into piles of gravel with a bit a clay, this is all glacial till.

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P.E. Metallurgy, Plymouth Tube

 

[ajk1]

To Edstainless - ok, that may explain their success. The gravel will be relatively free draining relative to clay and less frost susceptible. Thanks for your help. Much appreciated.

 

[OldBldgGuy]

ajk1
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.

 

[ajk1]

To OldBldgGuy:

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.

 

[ajk1]

To OldBldgGuy:

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?

 

[OldBldgGuy]

Sorry if I wasn't clear. I meant that some shallow foundations are insulated to replace the soil frost cover, and some are not, and the trick is knowing when either is appropriate or necessary. Considering what seasonal movement might do to something is key, and considering how you have to recover from the movement or mitigate any potential differential movement is also crucial. For instance, in most cases seasonal movement of a monument is inconsequential but differential movement is critical. That's where you want to be sure that the snowshoes are big enough to always keep you upright, without being so big you can't afford to buy them and you can't wear them. Knowing what kind of snow you're walking on is pretty important too.

 

[ajk1]

To OldBldgGuy - OK, now I understand and I am in general agreement with you. Thanks.