Best method for supporting castle walls

Yes, folks, actual castle-style walls consisting of LeFarges' 2'x2'x6' v'eed stackable concrete monolith blocks set end-to-end(4,000lbs each.) The walls are designed ~40'x36'x45' high interspersed with windows and doors set in 3/4" thick steel encasements to support any surrounding blocks. The natural bed on which the walls will be built is colorado sandstone and is basically homogenous with very few segmental cracks running at angles to the expected footer line. Park county has given me their basic requirements for concrete footer dimensioning as a starting point, but I'd like to ask the following questions as they have never been approached about a structure with such heavy walls:

Should I have the sandstone leveled and stack the blocks on the bed directly; this would require dramatic leveling as one side of the footer line is about 6' higher than the other?

Should I use monolithic, stepped concrete pours with 1/2" rebar tie-ins every 18sq", and if so, what dimensions should the footer be for such massive wallings?

OR, should I proceed with leveling the high side of the sandstone bed, and use stepped concrete footers on the downside as described above? Something completely different?!

Please understand that all work will be professionally done. I'd just like to be able to talk "apples to apples" with the contractor/engineer/designer about this footer project, and thus the questions/answers will simply go to them for discussion. Thanks so much, ya'll!

 

Are the walls actually a clear 45' high with no lateral support or are they supported by other intersecting walls and floors? If they are 45' high without any stabilization, you will need some bracing or slightly thicker wlls. Lateral loads will be your main concern, not vertical bearing.

Unless you run into arbitrary, specific code requirements, a concrete footing is really not necessary. The only purpose for the concrete would be for leveling if you do not have soil between the block and the limestone. All the concrete would do, would provide a leveling layer, just as mortar does for smaller masonry units. On a building the size you mentioned, a 6' maximun elevation is not a big problem, so leveling may be in order.

The height of the building is not that great considering the units proposed.

I have seen many 10 t0 20 story masonry and precast buildings placed on similar block in many counties where it is common to not use poured in place footings on native soils. Block similar to yours are commonly used for the foundation/footings in Russia on residential apartments and commercial/industrial construction in place of poured concrete footings.

A loadbearing non-reinforced brick wall (no steel or concrete columns) for an apartment building of 15 to 25 stories has 22" thick unreinforced brick walls if I recall correctly. These buildings have traditionally been supported on precast concrete footing block, so you are really not stretching the limits (only U.S. traditions)

Your big problem will be to address what type of method of construction will be required to "tie" the individual block/masonry units together above grade. Do not rely on embedded steel weld plates. Because of the mass and area, you may have quite low shear and compression stresses. I assume you will be using some type of mortar to account for irregularities. One solution would be to hire Egyptian pyramid builders or Roman aquaduct builders.

Because of the method of pouring the large block and the tolerences, some sort of leveling mortar may be required to develop the true strength of the block.

If your engineers are not familiar with this type of construction, it will be easy for them to get lost in the "over-engineering" using simplistic, unreasonable assumptions. - It is only an unreinforced masonry building made out of larger block than normal in the U.S. The height to thickness ratios may be slightly higher, but the stabilzing loads are more beneficial.

Sounds like a great, interesting project.

Dick

 

The blocks are v'eed both on the ends and top/bottom; stacking was originally not going to be 'brick-pattern'. The blocks were going to be mortared with an ad-mixture of concrete and other components necessary for such blocks(latex, epoxy, who knows what??? LOL!). The structure will have four floors and the ceiling ~9' apart as lateral supports, using hardwood beams and heavy plywood plates surfaced with hardwood coverings. The main floor would be as the upper floors, floating above the bedrock. I had considered stacking the blocks along their 2' line, making the walls 6' thick, but the numbers of blocks became grossly large and most difficult to design out the steel window and door encasements. I am a little confused as to not using the steel plates? Where is this in the design process? Is there a website that has extensive images and info on existing structures using these blocks, or ones similar as you mentioned? Thanks so much!

 

What you are building is not really big or "Earth shaking". It is a very basic gravity walled masonry structure.

It will be stronger and easier to build in runnung bond (brick pattern). The cute "vees" are nice little guides and will not add anything to the strength of the building. I know they are traditional on the molds for "comeback concrete" block used for non-building construction.

Normal mortar will be adequate. A latex additive or epoxy(totally rediculous) would contribute nothing. All of your stresses will be quite low in comparison to modern masonry capabilities.

The 2' is more than enough thickness for the walls.

The steel may form a cute frame to finish off a door or window, but is not needed unless you are trying to have opening totally out of character with the building you are describing. With 6' long units, you do not need steel reinforcement over a reasonable opeing. The masonry "arch action" removes almost all load over and opening if you have a higher ceiling. The Taj Mahal is an example of a 700 year old non-reinforced masonry domed structure with a marble veneer.

What you have is a very basic structure that can easily be constructed without the need of any Roman or Egyptian web sites (LOL).

Your engineer should just keep it basic, although some would try to make it difficult.

If it is for public use, you may expect code interpretation problems since it is not a normal "cookie cutter" design that a typical plan checker can understand. Your engineer may have to sit down and explain it to him/her.

Dick

 

I'm guessing you want electrical service in your castle?

 

Thanks for that! Yes, the place will have electricity, but since we are off-grid, most of the equipment is interior with proper venting for the batts/generator. Plumbing is to be routed outbound via channels under the floors/blocks in the rockbed. Interior wiring will be housed in wooden casements/conduits running along the floor as nice baseboards. Heating is to be a single flue interior chimney with adjoining fireplaces on each level. Cooling the place does not seem to be an issue. Ionic Breeze units will handle the O2 demands, dust, dander, ect. All the windows and doors are oversize, matching a single or multiple block opening. The view from the ridge on which the structure will be built has a magnificent 280deg panorama, so we'd like to make use of the sunlight and views as much as possible....out of character? Yes. If the 'brick layering' is to be done, how does one make smooth cornerings, by cutting the existing blocks, or forming special corner units? There shouldn't be any code issues as the structure is a home and not for public use. Anything else? Thanks so much!!!!

 

If you need special units for corners or openings you should cast them.

It would be wise to verify that the building is not under a code requirement. Being a residence does not necessarily eliminate the requirements, but could redefine them. This goes beyond just simple building codes, but could include satitary and occupancy permits.

A 45' high castle on a ridge may be noticed. If your nearest neighbor is a county official living 15 miles away that does not like the appearance, you could have code questions.

Code violations can be costly, up to the price of having someone tear it down and remove the debris.

It is better to verify first.

Dick

 

I have done some design work on a home using a similar sysem is why I ask about the electricity. In the end, that was the deal breaker. Why go through the trouble and expense (and, yes, this method of construction is very expensive compared to a stick house), if the interior walls have to be furred out anyway.

Remember also, that unless you plan on pouring your own block, you will have something that looks more like a prison than a castle.

That said, there are ways to run the electricity in the walls and ways to provide joist pockets for the floors, provided you make your own block.

As an aside, you should be able to build the entire structure using standard length block, along with some 2x2x2 units, so long as you keep it modular to the 2' dimension (2' or 4' wide windows, 4'x8' doors (rough openings)). An even better looking design would be to mold 2', 4' and six foot long units and lay them in a "random" pattern.

 

Excellent reality checks....THANKS! I'll be sure and get with Park County once I talk to the local foundations engineer here with your ideas, thoughts, and concerns. Please feel free to add anything to this discussion, as I consider all your thoughts vitally important to finishing this home correctly. You've already been tremendously helpful to me and my family....KUDOS!!!!

 

Well, I just finished removing the top, loose rocks and prepped the area for the foundation engineer to inspect. To my simple eye, the sandstone base is more tightly packed boulders than homogenous material. Ya'll think this will affect the concept of leveling the sandstone rather than setting concrete footers? Thanks!

 

It can definitely affect the support and stability of the walls.

Since you are hiring an engineer, rely on his opinion. If he is not a soil/foundation engineer, hire one.

Dick

 

Yes, the gent who is coming out to inspect is an actual foundations engineer and comes highly recommended. Wish us luck!

 

You may want to contact these guys:

http://www.guedelon.com/

They are building a castle the old fashioned way.

 

Could you check that addy for me, boss? I can't seem to pull it up. Thanks!

And also, could ya'll tell me if there is a way to safely stack these blocks using only their V's instead of brick-pattern? Making those corners would be tedious at best. If I have to go that route, so be it, but................

 

It worked last night, but it was on Slade, so it is probably just hammered. Give it a few days to recover.

As to the corners, it should be simple enough to use a chipping hammer and remove the outie part of the vee. You will want to use coursing on the blocks, for sure.

 

Roger that, boss......thanks!

Soooo.......the coursing is necessary even though the lateral supports consist mostly of the floorings and ceiling? Just trying to understand. Thanks again!


Ah, skip it......years of masonry can't be wrong....I'll course as suggested!


Of course(LOL!), this begs the question.......how does one cut the blocks to form straight door edges?! I'm assuming someone would have to cut the doorway once the wall is formed? I know trying to hoist cut blocks would be a major pain due to their unevenness from the existing hoist-point. I reckon I could have 2'x2'x2' and 2'x2'x4' blocks formed for those pieces. Ya'll sure I couldn't just straight stack??? LOLOLOL!

 

Stack bond is when the joints line up vertically. The problem is that if you use a stack bond, you have no horizontal continuity. With a stagger bond (1/3 bond in your case), there is no clear vertical path of weakness in the wall.

 

And I assume that ANY vertical weakness line is unwanted, even with blocks that weigh 4K apiece?

 

Yes. Do some research on ancient building methods. They figured this out thousands of years ago.

 

You are contemplating a very unique structure. You will have to decide if you want to build a structure to prove or establish something (living concept, use of waste materials or tradition) or to create an appearance compatible with some concept. - It sounds like you have several choices:

1. Contact the descendents of those that have built castles, acqueducts and pyramids.

2. Build out of modern split concrete block so it looks like a castle.

Either way will be easier and cheaper.

The concept of using massive pieces of precast concrete for a foundation is well developed and proven where there is no access to ready-mix concrete. In Russia, they have built many 20 story buildings on massive concrete block foundations with little poured concrete. They have aged well and performed well except for the windows and roofs.

It sounds like you are getting well ahead of the professionals you plan to hire to guide you. If you need them, listen to them and THEN decide on you direction.

Dick

 

Sound advice from both of you....thanks again. I really appreciate your patient responses on this matter.