Foundation Load Tables for Arch Buildings
If you approve an arch building quote without base reactions, you’re guessing at footing and anchor cost. I’d want the reaction table before anything else, because it tells me what the building sends into the ground: downward load, uplift, side force, and overturning moment.
Here’s the short version:
- I use the load table to check footings, anchors, grade beams, and slab-edge support.
- I make sure reactions are tied to the actual building: span, height, arch shape, spacing, openings, cladding, and local snow and wind.
- I do not compare supplier numbers unless the basis matches: service vs. factored loads, units, code edition, support location, and sign convention.
- I check whether each value is per arch leg, per frame, per base plate, or per metre. That one detail can change cost by a lot.
- I confirm the numbers against site data like soil bearing, groundwater, drainage, settlement risk, and frost depth.
- In Canada, I also want the AHJ-approved code basis, the right CSA S16 edition, and sealed drawings from the engineer licensed in the project province or territory.
A missed reaction type can lead to the wrong concrete scope. For example, a quote may look fine on roof snow alone, but an arch can still push hard at the base and pull upward under wind. That means your lowest building price can turn into a higher installed cost once excavation, reinforcing steel, anchors, and frost protection are priced.
Before I trust any table, I confirm:
- Loads: dead, snow, wind, seismic
- Reactions: compression, uplift, shear, thrust, moment
- Units: kN, kN/m, kN·m, mm
- Cases: service and factored
- Documents: reaction summary, sealed drawings, anchor layout, geotechnical info
| What I check first | Why it matters |
|---|---|
| Vertical reaction | Footing bearing and settlement |
| Uplift | Anchor rods and hold-down design |
| Horizontal thrust/shear | Sliding, grade beam, and support restraint |
| Overturning moment | Stability and compression distribution |
| Governing load case | Tells me which combo controls each peak |
| Code and seal | Confirms permit and design basis |
If I were reviewing quotes today, on September 28, 2026, I’d treat the reaction table as a pricing document, not just an engineering attachment. It helps me compare suppliers on the part buyers often miss: what the building will cost below grade, not just above it.
What a Foundation Load Table Contains
Arch Building Foundation Load Types: Directions, Purposes & Units
A foundation load table is a reaction summary. It shows what each support sends into the foundation.
That matters because the same building footprint can lead to very different foundation demands. So this table shouldn’t be treated like a throwaway appendix. It belongs in the quote. Use it to compare support reactions, not just the building’s total loads.
Common reaction entries and units
Most load tables include a few different force types. Each one should show the direction, the sign convention, and the support location. If that information is missing, it’s easy to compare numbers that don’t mean the same thing.
- Dead-load reaction: permanent building weight and fixed components.
- Snow-load reaction: vertical force from roof snow, including drift or accumulation cases.
- Vertical reaction: combined upward or downward force at a specific support or frame line.
- Wind-induced compression: downward or inward force from wind pressure.
- Wind uplift: upward force that can govern anchor bolt design even on a heavy building.
- Horizontal thrust or shear: lateral force transferred into the foundation; important for arch geometry and base restraint.
- Seismic reaction: horizontal force, which can also include vertical effects, where seismic design applies.
- Anchor-bolt tension: axial, upward force used to verify anchor steel, embedment, concrete breakout, and hold-down capacity.
- Anchor-bolt shear: horizontal or transverse force used to verify anchor shear, base plate, grout, and concrete transfer.
- Base or overturning moment: rotational demand used to determine compression distribution, uplift tendency, and foundation stability.
- Line reaction: distributed along a foundation edge or wall, used to design continuous strip footings, grade beams, or foundation walls.
| Load type | Direction | Purpose | Typical units |
|---|---|---|---|
| Dead-load reaction | Vertical, downward | Sizes foundations for permanent building weight and checks net bearing | kN, kN/m |
| Snow-load reaction | Vertical, downward | Checks footing bearing, settlement, and structural support under snow or drift | kN, kN/m |
| Vertical reaction | Vertical, upward or downward | Shows the combined reaction at a support or frame line | kN, kN/m |
| Wind-induced compression | Vertical or inclined, downward | Checks compression, bearing, and base-plate transfer under wind pressure | kN, kN/m |
| Wind uplift | Vertical upward | Sizes anchors, hold-downs, reinforcement, and foundation resistance to uplift | kN, kN/m |
| Horizontal thrust or shear | Horizontal | Checks sliding, lateral resistance, shear transfer, and arch-support restraint | kN, kN/m |
| Seismic reaction | Horizontal; can also include vertical effects | Checks lateral resistance, anchorage, foundation sliding, and overturning where applicable | kN, kN/m, kN·m |
| Anchor-bolt tension | Axial, upward | Verifies anchor steel, embedment, concrete breakout, and hold-down capacity | kN |
| Anchor-bolt shear | Horizontal or transverse | Verifies anchor shear, base plate, grout, and concrete transfer | kN |
| Base or overturning moment | Rotational | Determines compression distribution, uplift tendency, and foundation stability | kN·m |
| Line reaction | Distributed along a foundation edge or wall | Helps design continuous strip footings, grade beams, or foundation walls | kN/m |
Before you compare quotes, convert everything to one unit system. Then check what each number applies to. Is it per arch leg, per frame, per base plate, or per metre of building length? That one detail can change the whole read of the table.
It also helps to watch for supports that don’t match the rest of the building. End frames, openings, bracing lines, and uneven snow or wind cases can produce reactions that differ from interior frames.
Service loads, factored loads, and governing cases
Service reactions are unfactored. Factored reactions use code load combinations for strength design. If one quote shows service loads and another shows factored loads, the comparison falls apart.
You’ll also want to know which load case controls each demand. Compression, uplift, shear, and moment don’t always peak under the same combination. One case may drive uplift, while another drives shear or overturning.
Ask each provider to name the governing case for every peak value. That gives the foundation engineer the right reaction set for the job.
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How Engineers Use Load Tables to Design a Foundation
From building geometry to foundation checks
Once the load table is confirmed, engineers compare it with the actual building and foundation layout. That means checking the building geometry, steel specification, frame spacing, openings, and base connection details. If any of those inputs are different from what the supplier assumed, the reactions may not match the forces that are actually going into the ground.
After that, the engineer assigns each reaction component to the base-plate locations shown on the foundation layout. From there, they check bearing, sliding, uplift resistance, and the capacity of both the anchors and the concrete.
The arch profile matters too. A steel arch can send a lot of horizontal thrust and uplift into the base connection, not just vertical gravity load. That’s why the horizontal reaction column in a load table deserves just as much attention as the vertical one.
Site conditions, frost depth, and geotechnical coordination
After geometry, the next limit is the site itself. Reaction values on their own don’t say much unless they’re checked against site data. The engineer needs the soil bearing capacity, groundwater conditions, drainage, settlement risk, and frost susceptibility for the specific property.
Frost depth is a good example of why generic details only go so far. The required founding depth depends on soil type, drainage, climate, and whether the building is heated. The National Building Code is clear that, unless a foundation is specifically designed to handle frost action, its bearing surface must sit below the level where frost could cause damage.
A supplier’s standard foundation sketch is just a starting point. Local code rules and project-specific inputs control the design, so the foundation has to be treated the same way. Use the reaction table alongside the geotechnical report, code values, and a licensed professional engineer’s foundation design.
How to Compare Arch Building Quotes Using Reaction Data
Only compare quotes after the design assumptions line up. If one supplier is pricing one set of loads and another is pricing something else, the totals don’t mean much. Use one schedule so every quote is checked against the same basis.
Build a like-for-like comparison schedule
Match the same reaction types already listed in the load table. This schedule makes each supplier show their assumptions up front, before you look at totals.
Quote-comparison table
| Field | Quote A | Quote B | What to verify |
|---|---|---|---|
| Building width, length, and clear height | – | – | Same inside or outside dimension basis |
| Arch model/profile and steel thickness | – | – | Same arch geometry, grade, and corrosion protection |
| Arch spacing and support arrangement | – | – | Frame spacing and number of supports |
| Assumed foundation type and base restraint | – | – | Slab, strip footing, isolated pads, piles, or other support |
| Dead-load assumptions | – | – | Shell, cladding, liner, and permanent equipment |
| Snow-load assumptions (S_s, S_r, exposure, and accumulation) | – | – | Site-specific ground snow load and roof/snow factors |
| Wind load assumptions and exposure category | – | – | Wind pressure, terrain, internal pressure, and direction |
| Seismic parameters and importance category | – | – | Site class, seismic inputs, and load path |
| Vertical service reaction: compression | – | – | Direction, location, and sign convention |
| Vertical service reaction: uplift | – | – | Wind case, anchor arrangement |
| Horizontal service reactions (both directions) | – | – | Shear magnitude and governing case |
| Vertical factored reaction: compression | – | – | Confirm factored, not service |
| Vertical factored reaction: uplift | – | – | Anchor design and sign convention |
| Horizontal factored reactions and moments | – | – | Required for footing stability |
| Anchor tension, shear, and combined forces | – | – | Per anchor, per group, or per base plate |
| Governing load combination | – | – | Dead + snow, wind uplift, seismic, or other |
| Units and force-direction convention | – | – | kN/kPa/mm vs. lb/kip/psf/in |
| Code edition and provincial adoption | – | – | Current NBCC edition and local amendments |
| Sealed drawings by the responsible P.Eng. in the project province | – | – | Responsible P.Eng. and province confirmed |
| Foundation, concrete, reinforcing steel, anchor hardware, excavation, drainage, and frost protection | – | – | Included, excluded, or allowance only |
Keep foundation scope and pricing separate. That way, reaction-driven civil costs stay in plain view instead of getting buried in one lump-sum number.
What to confirm before trusting the numbers
If a quote leaves out site-related load categories, it isn’t comparable. Simple as that.
Check units first. kN, kPa, and mm are not the same as kip, psf, or inches. A unit mismatch can throw off the whole review.
Service reactions are used for serviceability. Factored reactions are used for strength, anchorage, and stability. That split matters, especially when you’re checking footings, anchors, and uplift.
After that, look at the code basis behind the reactions. That’s the next place where two quotes can look similar on paper but be built on different assumptions.
Canadian Code Requirements, Key Documents, and Next Steps
Code-based values and who must confirm them
Before you approve the foundation, confirm three things: the AHJ-approved NBC edition, any provincial or territorial amendments, and the project engineer’s design basis. The NBC only applies when the local AHJ has adopted it, along with any local amendments.
That means the code basis should never be guessed. Confirm it directly with the AHJ and the responsible P.Eng. before foundation approval. Also check which CSA S16 edition the project uses, and make sure that same edition appears on the sealed calculations.
Document checklist before approval
"Engineering included" sounds good, but on its own, it doesn’t tell you much. What matters is whether the sealed documents are clearly named in writing.
Use the same code basis and load assumptions from the quote comparison when you review the documents below. If one document uses one set of assumptions and another uses something else, the whole package can go sideways fast.
Document-verification table
| Document | Who provides it | What the buyer should confirm |
|---|---|---|
| Project-specific foundation reaction table | Building provider or responsible structural engineer | Confirm the project, dimensions, support locations, load cases, units, and whether values are service or factored |
| Structural calculations or reaction summary | Responsible professional engineer | Applicable code edition, governing combinations, assumptions, and match to the quoted building |
| Sealed building drawings | Responsible professional engineer or design professional | Seal, jurisdiction, issue date, intended use, member sizes, openings, bracing, and permit completeness |
| Sealed foundation drawings | Foundation engineer or project structural engineer | Footing or slab size, reinforcement, anchor rods, frost protection, drainage, and soil assumptions |
| Anchor-bolt layout | Building provider and foundation designer | Bolt coordinates, diameter, grade, embedment, projection, tolerances, base plates, washers, and required grout |
| Project design criteria sheet | Provider’s engineer or project engineer | NBC or provincial basis, site location, snow, wind, seismic, occupancy, exposure, importance, and load assumptions |
| Soil or geotechnical information | Geotechnical consultant, owner, or foundation engineer | Soil profile, allowable bearing, frost depth or protection method, groundwater, settlement risk, and lateral resistance |
| Foundation inclusions and exclusions | Building provider and foundation contractor | Who is responsible for each scope item and any deficiency correction |
| Installation requirements | Building provider | Base preparation, levelling, temporary bracing, bolt tightening, erection sequence, and weather limitations |
| Engineer licence and jurisdiction confirmation | Responsible engineer or engineering regulator | Engineer’s name, discipline, seal, licence number or registration, and authorisation to practise in the project province or territory |
If any of these documents is missing before concrete is placed or irreversible materials are ordered, stop. That’s the point where small paperwork gaps can turn into expensive field fixes.
Once the documents line up, the foundation engineer can finish the footing and anchor design. Quonset Canada connects visitors with Canadian building providers who can answer questions and offer free quotes, which can help you gather project-specific information and find the right engineering contacts for your province or territory.
Conclusion: Match Assumptions, Confirm Code Values, and Use Project-Specific Reactions
Foundation approval comes down to matched assumptions, sealed documents, and AHJ-confirmed code values. Quote comparisons only mean anything when the assumptions, units, reaction locations, load levels, and scope all line up.
Before a single cubic metre of concrete is placed, confirm the applicable Canadian code, local permit requirements, soil conditions, and the role of the professional engineer.
FAQs
What is a foundation load table?
A foundation load table is a code- and site-based summary of the forces an arch building’s foundation needs to resist. It usually lists downward loads, uplift, and lateral thrust at the base or anchor points, often in design units like kPa.
Providers use this table to size anchors and base parts, and to spell out what the concrete slab or footing must be engineered to handle. Buyers should make sure it matches the project’s exact postal code or GPS location, along with the final P.Eng.-stamped foundation design for local soil and frost conditions.
Are the reactions service or factored loads?
Yes. The reactions shown on anchor bolt plans are service factored loads. They show the downward, uplift, and lateral forces the foundation must be engineered to resist.
Because these values depend on your site’s snow, wind, and seismic conditions, give them to your local P.Eng. Then make sure your foundation drawings match the manufacturer’s anchor bolt reaction plan exactly.
Which code values should I confirm in Canada?
To confirm the NBCC climatic design values for your arch foundation load tables, I need the exact project address or postal code.
Please send:
- Full site address, or
- Canadian postal code
Then I can confirm the site-specific:
- Ground snow load (Ss) in kPa
- Rain-on-snow load (Sr) in kPa
I can also confirm whether the engineered package includes:
- P.Eng.-stamped drawings
- CSA A660 certification
- Foundation and anchor sizing that accounts for:
- frost depth
- outward thrust
- site loading tied to your location
If you already have a quote, spec sheet, or drawing set, you can paste that here too. I’ll help you check it line by line.