2.4 Checklist for Design and Construction of Basements

This checklist serves as a chapter summary, helps review the completeness of construction drawings and specifications, and provides general guidance on project management. The checklist could be used many ways. For example, use one set of blanks during design and the second set during construction inspection. Note that not all measures are necessary under all conditions. Use different symbols to distinguish items that have been satisfied (+) from those that have been checked but do not apply (x). Leave unfinished items unchecked.

SITEWORK

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Locate building at the highest point if the site is wet

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Define “finish subgrade” (grading contractor), “base grade” (construction contractor), “rough grade” level before topsoil is respread, “finish grade” (landscape contractor)

____ ____

Establish elevations of finish grades, drainage swales, catch basins, foundation drain outfalls, bulkheads, curbs, driveways, property corners, changes in boundaries

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Establish grading tolerances

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Provide intercepting drains upgrade of foundation if needed

____ ____

Locate dry wells and recharge pits below foundation level

____ ____

Establish precautions for stabilizing excavation

____ ____

Establish limits of excavation and determine trees, roots, buried cables, pipes, sewers, etc., to be protected from damage

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Confirm elevation of water table

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Determine type and dimensions of drainage systems

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Discharge roof drainage away from foundation

____ ____

Remove stumps and grubbing debris from site

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Provide frost heave protection for winter construction

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Call for test hole (full depth hole in proposed foundation location)

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Locate stakes and benchmarks

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Strip and stock pile topsoil

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Define spoil site

FOOTINGS

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Position bottom of footing at least 6 inches below frost depth around perimeter (frost wall at garage, slabs supporting roofs, other elements attached to structure). Make sure footing is deeper under basement walkouts

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Confirm adequacy of footing sizes

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Do not fill the overexcavated footing trench

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Install longitudinal reinforcing

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Reinforce footing at spans over utility trenches

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Do not bear footings partially on rock (sand fill)

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Do not pour footings on frozen ground

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Indicate minimum concrete compressive strength after 28 days

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Call out elevations of top of footings and dimension elevation changes in plan

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Use keyway or steel dowels to anchor walls

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Dimension stepped footings according to local codes and good practice (conform to masonry dimensions if applicable)

____ ____

If using a single footing drain outside the footing, provide weep holes (minimum 2-inch diameter at 4 feet to 8 feet on center)

____ ____

Provide a capillary break between footing and foundation wall

STRUCTURAL DESIGN

Confirm wall engineering and accessories:

____ ____

Wall sized to resist height of fill and seismic loads

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Anchor bolt requirements for sill plate (minimum code)

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Anchors for joist ends (typically 6-foot spacing)

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Beam pocket elevations, dimensions, details

____ ____

Top of wall elevations and changes in wall height

____ ____

Brick shelf widths and elevations

Determine concrete specifications for cast in place walls:

____ ____

Determine minimum compressive strength after 28 days

____ ____

Determine maximum water/cement ratio. (Note: add no water at site)

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Determine allowable slump

____ ____

Determine acceptable and unacceptable admixtures

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Determine form-release agents acceptable to WPM (waterproof membrane) manufacturer

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Establish curing requirements (special hot, cold, dry conditions)

____ ____

Establish surface finish requirements and preparation for WPM (plug all form tie holes)

____ ____

For shrinkage control: use horizontal reinforcing at top of wall and/or control joints

____ ____

Design width of wall to resist height of fill, seismic loads, and loads transmitted through soil from adjacent foundations

____ ____

Use two-way reinforcing (horizontal and vertical) for strength, watertightness, termite and radon resistance

____ ____

Establish anchor bolt depth and spacing requirements, and install accordingly

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Provide cast-in-place anchors for joist ends

____ ____

Establish beam pocket elevations, dimensions, details

____ ____

Determine top of wall elevations and changes in wall height

____ ____

Determine brick shelf widths and elevations

Determine concrete masonry wall specifications:

____ ____

Specify mortar mixes and strengths

____ ____

Size walls to resist height of fill, seismic loads, loads transmitted through soil from adjacent foundations

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Grout top courses of block to receive anchor bolts

____ ____

Grout bottom course(s) up to the level of the top of basement slab

____ ____

Provide a grout course at each brick ledge

____ ____

Indicate special details for proprietary masonry systems

____ ____

Ensure that the surface quality is suitable to WPM

____ ____

Prepare exterior surface for application of dampproofing or WPM (special preparation consisting of cement parging, priming)

____ ____

For crack control, use bond beam or horizontal joint reinforcing

 

FLOOR SLAB

____ ____

Determine minimum compressive strength after 28 days

____ ____

Determine maximum water/cement ratio. (Note: add no water at site)

____ ____

Determine allowable slump

____ ____

Determine acceptable and unacceptable admixtures

____ ____

Establish curing requirements (special hot, cold, dry conditions)

____ ____

Determine surface finish

____ ____

Provide shrinkage control: WWF (welded wire fabric) reinforcement or control joints

____ ____

Provide isolation joints at wall perimeter and column pads

____ ____

Provide vapor retarder under slab

____ ____

Compact fill under slab

BACKFILLING AND COMPACTION

____ ____

Establish minimum concrete strength or curing prior to backfilling

____ ____

Use high early strength concrete if necessary

____ ____

Install temporary wall support during backfilling

____ ____

Establish condition of fill material (if site material stays in clump after soaking and squeezing in hand, do not use as backfill)

____ ____

Determine proper compaction

____ ____

Cap backfill with an impermeable cover

SUBDRAINAGE

General considerations. Footing drains (1) draw down the ground water level; (2) prevent ponds of rainwater and snow melt in the backfill. The underslab drainage layer (1) conveys rising groundwater laterally to collecting drain lines; (2) acts as a distribution and temporary storage pad for water that drains through the backfill and would otherwise form ponds at the bottom.

____ ____

Use gravel pad and footing weep holes if a single, exterior footing drain is used.

____ ____

Position high end of footing drains below underside of floor slab (Note: outside footing placement is preferred for drainage; inside placement is less susceptible to failure)

____ ____

Ensure footing drain is pitched

____ ____

Lay footing drain on compacted bedding (minimum 4 inches thick)

____ ____

Set unperforated leaders to drain to outfall (hand backfill first 8 inches to avoid damaging pipe).  If daylighting is not possible, drain to a sealed sump.

____ ____

Ensure that transitions are smooth between pipes of different slopes

____ ____

Separate surface, roof, and foundation drain systems

____ ____

Call out gravel or crushed stone envelope around drainpipe and wrap with a synthetic filter fabric

____ ____

Locate clean-outs for flushing the system

____ ____

Install porous backfill or wall-mounted drainage product

____ ____

Provide minimum 4-inch-thick gravel or stone layer under slab

____ ____

If large flow of water is anticipated, use curtain (French) drain to intercept

MOISTUREPROOFING

General considerations. Waterproofing is usually recommended for all below-grade living and work spaces. Dampproofing provides a capillary break and serves as a vapor retarder. Waterproof membranes (WPM) dampproof, but dampproofing does not waterproof.

____ ____

Either dampproof or waterproof walls

____ ____

Place a polyethylene vapor retarder under floor slabs

____ ____

Place a continuous WPM (waterproofing membrane) under slab for basements below groundwater (special detailing and reinforcement required for support)

____ ____

Install control and expansion joints according to recommendations of WPM manufacturer

____ ____

Provide protection board for WPM

THERMAL AND VAPOR CONTROLS

General considerations. Exterior insulation maintains the wall close to indoor temperature. This will tend to maintain a drier foundation wall, and keeps rubber and asphalt-based moistureproofing warm and pliable.  Difficulty of air sealing at the rim joist generally favors exterior insulation.

____ ____

Verify that wall insulation R-value and depth meet local codes at a minimum

____ ____

If used, specify exterior insulation product suitable for in-ground use

____ ____

Install protective coating for exterior insulation

____ ____

Install polyethylene slip sheet between soil and wall (nondrainage) insulation

____ ____

Place a fire-protective cover over combustible insulations if exposed on the interior

____ ____

Install infiltration sealing gasket and through-wall termite shield under sill plate

____ ____

Seal air leakage penetrations through rim joists

____ ____

Install an air barrier outside rim joist

DECAY AND TERMITE CONTROL

General considerations. Strategy: (1) Isolate wood members from soil by an air space or impermeable barrier; (2) expose critical areas for inspection. Pressure-treated lumber is less susceptible to attack, but is no substitute for proper detailing. Termite shields are not reliable barriers unless installed correctly.

____ ____

Pressure-treat wood posts, sill plates, rim joists, wood members in contact with foundation piers, walls, floors, etc.

____ ____

Pressure-treat all outdoor weather-exposed wood members

____ ____

Install dampproof membrane under sill plate and beams in pockets (flashing or sill seal gasket)

____ ____

Leave minimum 1/2-inch air space around beams in beam pockets

____ ____

Expose sill plates and rim joists for inspection

____ ____

Elevate sill plate minimum 8 inches above exterior grade

____ ____

Elevate wood posts and framing supporting porches, stairs, decks, etc., above grade (6-inch minimum) on concrete piers

____ ____

Elevate wood siding, door sills, other finish wood members at least 6 inches above grade (rain splash protection)

____ ____

Separate raised porches and decks from the building by 2-inch horizontal clearance for drainage and termite inspection (or provide proper flashing)

____ ____

Pitch porches, decks, patios for drainage (minimum 1/4 in/ft)

____ ____

Treat soil with termiticide, especially with insulated foundations

____ ____

Reinforce slab-on-grade

____ ____

Remove all grade stakes, spreader sticks, and wood embedded in concrete during pour

____ ____

Do not disturb treated soil prior to pouring concrete slab

____ ____

Reinforce cast-in-place concrete walls (with No. 5 bars) along the top and bottom to resist settlement cracking

RADON CONTROL MEASURES

General considerations. The potential for radon hazard is present in all buildings. Check state and local health agencies for need of protection. Strategies include: (1) passively or actively depressurizing soil and crawl space air pressure relative to the indoors; (2) soil gas retarding membranes; (3) provisions to activate passive soil depressurization systems. Since radon is a gas, its rate of entry through the foundation depends on suction due to stack effect, HVAC system imbalances, exhaust devices, and air leakage especially at high points in the building envelope.

____ ____

Provide separate outdoor intakes for combustion devices

____ ____

Install air barrier wrap around the envelope

____ ____

Seal around flues, chases, vent stacks, attic stairs

____ ____

Reinforce cast-in-place concrete walls (with No. 5 bars) along the top and bottom to resist settlement cracking

____ ____

For crack control in masonry walls, use bond beam or horizontal joint reinforcing

____ ____

Seal top of hollow masonry walls with solid block, bond beam, or cap block

____ ____

Parge exterior face of masonry walls

____ ____

Install continuous moistureproofing on the outside of masonry walls

____ ____

Reinforce slab-on-grade

____ ____

Remove all grade stakes, spreader sticks, and wood embedded in concrete during pour

____ ____

Form perimeter wall/floor joint trough for pour-in sealant

____ ____

Place vapor retarder under slab

____ ____

Caulk joints around pipes and conduits

____ ____

Install sump pit with airtight cover

____ ____

Vent sump pit to outside

____ ____

Do not use floor drains, unless mechanical trap valves are used

____ ____

Lay minimum 4-inch-thick layer of coarse, clean gravel under slab

____ ____

Cast 4-inch-diameter PVC tubing standpipes (capped) into slab

PLANS, CONTRACTS, AND BUILDING PERMITS

____ ____

Complete plans and specifications

____ ____

Complete bid package

____ ____

Establish contractual arrangements (describe principals, describe the work by referencing the blueprints and specs, state the start/completion dates, price, payment schedule, handling of change orders, handling of disputes, excavation allowance, and procedure for firing)  Use signoff on work statements, work ready, and work finished quality assurance procedures.

____ ____

Acquire building permits

SITE INSPECTIONS DURING CONSTRUCTION

____ ____

After excavation and before concrete is poured for the footings

____ ____

After the footings have been poured before foundation wall construction

____ ____

After foundation construction and dampproofing before rough framing

____ ____

After rough framing

____ ____

After rough plumbing and electrical

____ ____

After insulation installation before drywall and backfilling in case of exterior insulation.

____ ____

Final