Stormwater management/drainage

Building Plans for a Dry, Radon-Free Foundation

How To Keep Water and Radon Out of Your Basement or Crawlspace: 8 Details that will keep your foundation dry and healthy

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    Ground Gutters

    Low-maintenance alternative to a roof gutter

    Posted on Aug 11 2009 by Michael Maines

    The rubble stone foundation walls wept every time it rained, creating a dank, humid basement. The destructive power of ice dams, and a huge, overhanging elm tree created maintenance issues, leaving our clients unwilling to replace the gutters original to the old two-story house. The lot sloping to the rear left the downhill neighbors’ yards saturated much of the year. How were we going to solve these problems? By installing a ground gutter system.

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    Image Credits:

    1. Fine Homebuilding

    Foundation Drains

    Footing Drains Keep the Basement Dry from the Outside

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    Footing-drain problems are expensive to fix

    Building codes require perimeter drains around the outside of basement footings. They are not difficult to install properly before the foundation has been backfilled, but they are costly and disruptive to put in after the fact.

    As long as you're going to protect the bottom of the foundation of a house from water, it's worth doing right.

    See below for:

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    Pick the right drain line

    The 4-inch black line that comes in coils is cheaper than rigid PVC pipe, but it’s not as crush-resistant, and the narrow slots in pipe walls are more likely to clog than the holes in rigid pipe.

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    Integrate water-management strategies

    The foundation drain shouldn't do all the work. If groundwater is managed well, underground drains become just one part of a bigger system. Carefully grading the yard can go a long way toward keeping water away. Surface drains and gutters can catch much of the water that does reach the house.

    Drainwater can work for you. If the grade allows drains to reach the surface, a rain garden might be a good option. Then water isn't just diverted, it also provides valuable irrigation to the landscape.

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    Backfill with quick-draining material

    It may be tempting to backfill a basement foundation with excavated soil, but it's best to place coarse, granular material like crushed stone or bank-run gravel against the foundation to encourage drainage. A cap of soil with a high clay content near the surface will encourage surface water to flow away from the foundation.

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    foundation drain

    The Code

    Sections 404, 405, 406, and 801 of the International Residential Code (IRCInternational Residential Code. The one- and two-family dwelling model building code copyrighted by the International Code Council. The IRC is meant to be a stand-alone code compatible with the three national building codes—the Building Officials and Code Administrators (BOCA) National code, the Southern Building Code Congress International (SBCCI) code and the International Conference of Building Officials (ICBO) code.) relate to foundations and below-grade habitable space. All code references are to the IRC unless otherwise specified.

    Concrete & CMUConcrete masonry unit. Precast concrete block used to build walls. CMUs have hollow cores that can be filled with concrete onsite for additional reinforcement. The use of stronger, more lightweight types of concrete such as autoclaved aerated concrete (AAC) is becoming increasingly popular in CMU manufacture. foundations that contain habitable or usable space need drains [405.1], unless there is good natural drainage [405.1X]. Use filter fabric over drain fields [405.1] and at least 2 inches of stone under pipes [405.1]. If the soil is expansive or collapsible, extend gutter downspouts 5 feet from the building or to an approved drainage system [801.3].

    Water-proofing, Damp-proofing, & Backfilling
    Below-grade basement walls need damp-proofing [406.1], but if the water table is high, use water-proofing instead [406.2]. Parge CMUs before damp-proofing [406.1], and lap and seal all joints in water-proofing [406.2].

    Don't backfill until foundation walls are anchored to the floor framing [404.1.7] (except walls supporting less than 4 feet of unbalanced backfill [404.1.7X]).

    Illustration: from Code Check Building 2nd Edition. click to buy .


    Keeping your basement dry pays many dividends: a dry basement is less likely to have mold, and the house may have better indoor air quality and fewer moisture problems in the attic. If you value these dividends, invest in high-quality, crush-resistant footing drains of an adequate diameter, and backfill the entire foundation with coarse granular material that drains well.

    It's better to run footing drains to daylight than to depend on a sump pump. While that may require more excavation, it's money well spent.


    Basement Water and Radon Pack
    Foundations Details

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    A footing drain the hard way
    These workers are excavating to install a footing drain on an older house — an awkward and expensive task. Most older houses on stone foundations were built without footing drains.


    LEEDLeadership in Energy and Environmental Design. LEED for Homes is the residential green building program from the United States Green Building Council (USGBC). While this program is primarily designed for and applicable to new home projects, major gut rehabs can qualify. -H ID2 (Durability Management Process) has prerequisites and 3 points for third-party certification of durability processes/practices.

    NGBSNational Green Building Standard Based on the NAHB Model Green Home Building Guidelines and passed through ANSI. This standard can be applied to both new homes, remodeling projects, and additions. Under Ch. 6, Resource Efficiency: 4 points for well-designed foundation perimeter drainage as part of durability measures (602.3).


    Run it to daylight
    Wet basements are common. Even some new-home owners complain of wet basements.

    If the slope of the building site allows, perimeter drains should connect to solid pipe that runs to daylight. The solid pipe should be sloped at a minimum pitch of 1/4 inch per foot, although a steeper slope is better. If there is more than 200 linear feet of foundation, add a second outlet or increase the size of the outlet pipe from 4 inches to 6 inches.

    When there isn’t enough pitch on the lot, the exterior drains should be connected to a sump pump in the basement via a 6-inch line that penetrates the footing near the sump location.


    Some sites are too wet for basements

    Water that seeps through a basement foundation or is forced upward by hydrostatic pressure can be collected in an interior drain system and routed to a sump for removal. However, if you know that groundwater is likely to be so big a problem that you have to relieve hydrostatic pressure with a perimeter foundation drain system and sump pump, you should seriously consider something other than a full basement foundation.


    Dig a trench as deep as the bottom of the footings.

    Lay filter fabric first. Unroll 6-foot-wide filter fabric along the trench, lapping the material up the sidewalls of the foundation. Spread the excess fabric away from the foundation.

    Add crushed stone and pipe. Over the filter fabric, lay a 3-inch layer of crushed stone, and then install the 4-inch rigid PVC pipe all the way around the foundation. The perforated pipe can be installed level. Window wells should be tied to the drain with solid 4-inch PVC. Add crushed stone to a level about 8 inches above the top of the footing, and then pull the excess fabric over the top of the stone and lap it against the foundation wall.

    Finish with coarse sand. A 6-inch layer of coarse sand spread on top of the fabric will prevent soil from washing into the fabric and clogging its pores.


    Create a sub-slab drainage field.

    Put down an 8- to 10-inch-deep layer of crushed stone before the basement floor is poured so that the entire area beneath the slab drains. Above the crushed stone, install a layer of extruded polystyrene insulation topped with a puncture-resistant vapor barrier, such as cross-laminated high-density polyethylene, which will prevent any below-grade moisture from rising into the basement.

    Install an plastic interior perimeter drain.

    In most cases, this consists of perforated 4-inch pipe. Proprietary drainpipe systems are also available, usually at a higher cost. All are designed to pick up water where the basement wall meets the the floor and drain it to a sump, from which it can be pumped out.

    Put in a sump pump. Water that’s collected on the inside of the foundation is piped to a cavity, or sump, set below the level of the floor. Use a pump that’s automatically activated by rising water to move water outside and away from the house. If local codes allow, the sump can be connected to the sewer system. (A sump pump could be connected to exterior footing drains if they run to daylight away from the house.)

    Battery-powered backup pump.

    In areas where flooded basements are common, a battery backup system for the sump pump ensures that the system will work when the power goes out. A maintenance or inspection schedule for the sump pump should be included in the homeowner’s manual. Installing a sump-pump pit cover that achieves an airtight seal will improve the home's air tightness and reduce the risk of radonColorless, odorless, short-lived radioactive gas that can seep into homes and result in lung cancer risk. Radon and its decay products emit cancer-causing alpha, beta, and gamma particles. entry.

    Image Credits:

    1. Krysta Doerfler/Fine Homebuilding #189
    2. Dan Morrison
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    Hardscapes: Patios and Driveways

    Patios and Driveways Need Solid Foundations

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    Permeable materials reduce water runoff

    Both driveways and patios can be built from a variety of durable materials. A solid base that drains water effectively is a good beginning.

    Longevity is only one consideration, however. Because driveways and patios often cover significant square footage, they can contribute to runoff problems both on and off the lot. Water that can't seep back into the ground ends up in stormwater drains and municipal treatment plants. Permeable materials, however, reduce runoff and erosion and help recharge underground water supplies.

    See below for:

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    Start with a solid foundation

    Eight inches of processed stone (sometimes called ABC stone or sure-pack) with particles ranging in size from dust to 1 1/2 inches in diameter provides the best base material for stone and paver patios and driveways. Place the stone in several thoroughly compacted 2- or 3-inch lifts and graded at a slope of 1/8 inch per foot so that water drains away from adjacent structures. Wetting the material during compaction will help lock together the variously sized particles. On unstable or clay soil, a layer of heavy-duty geotextile underneath the stone base will prevent differential settling.

    One inch of course sand place on top of the stone base provides a good setting bed for the pavers. All setting and base material should be sourced locally to reduce material and environmental costs.

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    A patio can be more than just a place to park your barbecue grill.

    In most climates, a patio could be a valuable living space, at least for part of the year. Consider using dry-laid pavers and complementary plantings, not just for added interest but to absorb stormwater runoff.

    Consider alternatives to the typical concrete slab. The portland cement in concrete is very high in embodied energyEnergy that goes into making a product; includes energy required for growth, extraction, and transportation of the raw material as well as manufacture, packaging, and transportation of the finished product. Embodied energy is often used to measure ecological cost. and accounts for a sizable fraction of the world’s human-generated carbon emissions. Therefore, it’s worth looking at concrete substitutes, such as fly ashFine particulates consisting primarily of silica, alumina, and iron that are collected from flue gases during coal combustion. Flyash is employed as a substitute for some of the portland cement used in the making of concrete, producing a denser, stronger, and slower-setting material while eliminating a portion of the energy-intensive cement required. More info or blast-furnace slag for portland cement in the concrete mix, and at strategies for using less concrete (e.g., open or spaced pavers). An “old-fashioned” driveway with two concrete drive strips surrounded by strips of groundcover is one possible approach. Salvaged stone, “urbanite”, and other reclaimed materials are excellent candidates for patios.

    Images from: Fine Gardening.

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    Good site preparation, then layers of stone and stone dust

    No matter what the finish materials are, the key to a long-lasting installation is careful site preparation. An ample base of compacted stone and coarse sand or stone dust creates a stable foundation that will keep the finish surface flat and trouble-free. A patio laid over soil that contains a lot of organic material or clay won’t last nearly as long.

    Sub-surface drainage. If the site is prone to flooding or heavy runoff, a curtain drain may be needed to divert water away from the finished patio.

    Excavation. To provide enough room for base layers, soil may have to be removed from the site. String lines that establish the finish grade and pitch across the width and length of the site to determine how much material must be removed. A depth of between 9 inches and 10 inches below finished grade leaves enough room for crushed stone and setting sand.

    Stone base. Crushed stone added in 2-inch to 3-inch layers and then compacted builds a stable base. A good option is something called ABC stone, which includes everything from dust to gravel up to 1 ½ inches in diameter. Each layer should be dampened and mechanically compacted. Look for a total depth of between 6 inches and 7 inches

    Coarse sand or stone dust. A 1-inch-thick layer of compacted coarse sand or stone dust over the stone base provides a flat foundation for the pavers. String lines help keep the surface flat and pitched correctly.

    Add pavers and more sand. Pavers can be laid in any pattern. The surface should be sloped away from the house to promote drainage (1/8 inch per foot is adequate). Once the pavers are in place, spread sand over the surface and vibrate it to lock the pavers in place.

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    No requirement for polyethylene vapor retarders

    While IRCInternational Residential Code. The one- and two-family dwelling model building code copyrighted by the International Code Council. The IRC is meant to be a stand-alone code compatible with the three national building codes—the Building Officials and Code Administrators (BOCA) National code, the Southern Building Code Congress International (SBCCI) code and the International Conference of Building Officials (ICBO) code. section 105 exempts driveways, patios, and sidewalks from permit requirements, many municipalities have local code or zoning requirements that specify setbacks and construction methods. Additionally, concrete porches and concrete walkways with steps that are exposed to the weather must satisfy section R402.2 and accompanying Table R402.2, which specifies the minimum compressive strength of concrete based on its weathering potential.

    According to section R506.2.3, polyethylene vapor retarders are not required under concrete driveways, walks, or patios, making pervious types of paving an attractive green option to conventional concrete flatwork.

    Like driveways, the IRC doesn’t require a polyethylene vapor retarder under patios, provided the space is unlikely to be enclosed in the future (section R506.2.3). This code exception makes the use of pervious paving materials an attractive option for outdoor living space.


    This stuff is heavy

    Because most, if not all, pavers are highly durable, transportation costs emerge as a key sustainability issue. All are heavy, so selecting pavers that are mined or manufactured nearby reduces transportation costs. Natural stone that is quarried regionally is preferable to shipping pavers long distances, even if local choices are somewhat less exotic.

    Using salvaged brick or natural stone pavers is a better environmental choice than buying new.

    Other landscaping materials

    Landscaping often includes terraced gardens and beds, especially on a sloping lot. Pressure-treated timbers are readily available, easy to work with and inexpensive. But a more attractive option are timbers made with recycled plastic. Not only will they last longer than wood but they help reduce the amount of waste plastic that goes to landfills.


    LEED for HOMESLeadership in Energy and Environmental Design. LEED for Homes is the residential green building program from the United States Green Building Council (USGBC). While this program is primarily designed for and applicable to new home projects, major gut rehabs can qualify. Permeable paving can contribute to maximizing the 4 points available in credit SS4 (Sustainable Sites).

    NGBSNational Green Building Standard Based on the NAHB Model Green Home Building Guidelines and passed through ANSI. This standard can be applied to both new homes, remodeling projects, and additions. Under Ch. 4 — Site Design: up to 5 points for permeable paving (403.5).


    Pavers are less likely to crack than monolithic slabs

    With an adequate base of compacted stone, a patio should last for many years with very little maintenance. There are three conventional categories for pavers: clay brick, concrete, and natural stone.

    Many types of pavers can handle repeated freeze-thaw cycles while providing an extremely wear-resistant surface. A monolithic concrete slab is more susceptible to cracking than a patio made from individual pavers.

    Clay brick. Brick is available in many colors and can be set in a variety of patterns. Because they are made from natural clay, brick pavers won’t fade in color and require little if any maintenance. Brick is highly durable and has a slip-resistant surface.

    Concrete. Less expensive than brick or natural stone, concrete pavers come in a variety of shapes and colors, including styles resembling brick and stone. Chamfered edges allow concrete pavers to be used on surfaces that must be plowed or snow-blown in winter, and de-icing products do not easily damage concrete. They can be used in all climates.

    Stone. Bluestone, granite, and limestone are types of stone that can be cut into pavers. Stone is probably the most expensive option, but it is also extremely durable. Colors and textures vary widely. The look of irregularly shaped stones is impossible to produce with manufactured products such as concrete or brick.

    Plastic pavers. In addition to these familiar materials, at least one manufacturer now produces pavers made from high-density polyethylene (HDPE) that is 100% recycled from postindustrial sources. Renew Resources offers the tiles in four colors and two sizes.


    Consider slope as well as surface porosity

    Driveways need a slight slope so that they shed water, but too much makes winter driving difficult. The grade should be no less than 2% (a change of 2 feet over 100 feet) but probably no more than 12%.

    Turning radius is another consideration. This can be as narrow as 15 feet in parking areas for small and midsize cars. But curves on long driveways may require a radius of 50 feet to accommodate fire trucks.


    Pavers and gravel let the water through

    Runoff from driveways and sidewalks is far from a trivial problem in suburban and urban neighborhoods where wide expanses of concrete and asphalt produce a great deal of water. Storm drains and waste treatment plants must be designed to handle a lot of water, and runoff also carries with it a variety of contaminants.

    Permeable surfaces allow at least some of the water to filter back into the ground while reducing the risks of erosion and flooding. Among the options for driveway surfaces:

    Plastic and concrete grids are placed on top of the driveway base and filled with gravel or topsoil and vegetation for a surface that resists erosion but still supports heavy vehicles. After it rains, the grid holds water until the water can seep into the ground. Plastic grids are often made from recycled materials and also can be used to reinforce and stabilize driveway bases beneath different finish materials.

    Pavers. Gaps between pavers let water and snowmelt pass through, so a base layer that drains well is key. Pavers can be made with concrete, brick, or stone. Compared with some other materials, pavers are relatively expensive, mainly because of the labor costs involved in their installation. Concrete pavers have a smooth surface, simplifying snow removal, and are available in many colors and patterns. Cobblestones, which are more expensive still, are generally uneven, posing potential problems for snowplows and snow blowers. But the look is estate-like classic.

    Gravel. This one of the cheapest driveway options, but it’s got some drawbacks. Without a good base and careful grading, expect ruts, potholes, and erosion after a heavy rain, and snowplows probably will push some of the surface stone into your yard. It can be difficult to snow-blow before the ground freezes solid. Fancy grades of crushed stone are better looking but share some of the same maintenance issues. On the plus side, a fresh surface is fairly easy to apply, and gravel often can be sourced locally, lowering transportation costs.

    Reclaimed asphalt. An option in some areas, reclaimed asphalt is recovered from road rebuilding projects and ground into a gravel-like mixture. It can be spread and packed by hand, or applied with the same equipment used to place asphalt. The material packs tightly to form a durable, wash-resistant surface.

    Porous asphalt and concrete. Leaving out the fine aggregates in a standard asphalt mix produces a porous surface through which water can drain freely. Durability appears comparable to conventional asphalt, even in cold-weather regions, but the mix is more expensive and not as widely used, limiting availability. One drawback is that the surface can be clogged by dirt and sand, and porous asphalt requires a more carefully designed base that can handle the water runoff. Using larger pea gravel and a lower water-to-cement ratio produces permeable concrete, which allows water to pass through quickly. As is the case with porous asphalt, finding a local contractor may be difficult.

    Concrete is an impermeable material. More expensive but also more durable than asphalt, it won’t get soft and gummy in the summer. But it’s susceptible to staining and can crack when placed over an inadequate base. Brushing the surface when the concrete has partially cured exposes aggregate for a more decorative appearance, but the treatment also means substantially higher costs and requires a skilled contractor. Concrete can be embossed with a pattern to make it look like pavers.

    Asphalt is impermeable, cheap, and the least green. It’s composed mostly of sand and gravel aggregate that’s held together with a bituminous (petroleum-based) binderGlue used in manufactured wood products, such as medium-density fiberboard (MDF), particleboard, and engineered lumber. Some binders are made with formaldehyde. See urea-formaldehyde binder and methyl diisocyanate (MDI) binder. . Although it’s not as durable as concrete, asphalt is more flexible ,so it’s not as likely to crack. Its dark color absorbs heat, so it melts snow faster than light-colored surfaces. Asphalt should be resealed every few years, but it can be resurfaced without tearing up the original pavement. It takes a number of months before asphalt cures, and the surface can get soft in the summer. An interesting nonpetroleum alternative is a resin-based pavement called Road Oyl Resin Pavement made by the Soil Stabilization Products Co. It’s produced from pine rosin and pitch and compares favorably with conventional asphalt for hardness and durability.


    The Center for Universal Design

    A Concrete-Paver Patio from the Bottom Up in Fine Homebuilding

    Road Oyl Resin Pavement asphalt alternative.

    Renew Resources plastic patio pavers.

    Image Credits:

    1. Chris Green / Fine Homebuilding #170
    2. Brian Pontolilo/Fine Homebuilding #195
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    Stormwater: Rain Gardens and Drywells

    Temporary Water Storage Helps Recharge Aquifers and Reduce Water Pollution

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    Image Credits:

    1. Michael Chandler
    2. Lee Ann White/Fine Gardening #74
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    Roof Gutters

    Choosing Rain Gutters: Wood, Metal, or Plastic?

    UPDATED 12/27/2011

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    Image Credits:

    1. Dan Thornton/Fine Homebuilding #177
    2. Andy Engel/Fine Homebuilding #125
    3. Charles Bickford/Fine Homebuilding #187
    4. Dan Thornton/Fine Homebuilding #125
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    Design a green or living roof system

    A green or living roof is a low-slope roof planted with vegetation.
    These carefully designed and built roofs usually consist of a structural roof deck layered with waterproofing, aggregate, lightweight soil, and vegetation. Sod, moss, or local wildflowers are favorites. Regular maintenance is needed to keep plants healthy.

    Green (vegetated) roofs absorb rainfall during storms and release the water slowly. This reduces storm-water surges and downstream flooding. Water management for a green roofRoof system in which living plants are maintained in a growing medium using a membrane and drainage system. Green roofs can reduce storm-water runoff, moderate temperatures in and around the building (by providing insulation and reducing heat island effect), as well as provide a habitat for wildlife and recreational space for humans. When properly constructed, green roofs can increase roof durability because the roof assembly’s air and water barriers are buffered from temperature fluctuations and UV exposure. requires the same attention to detail as any other low-slope roof.

    Manage stormwater with 'sheet flows'

    Disperse water runoff gently
    To reduce downstream flooding and keep pollutants out of local waterways, try not to direct stormwater into concentrated channels. It's better to design the edges of impermeable areas so water can disperse broadly, known as a sheet flow. Water can be directed into infiltration basins, vegetated swales, or vegetated filter strips. The idea is not to send streams of runoff across vegetated areas.

    Use planted swales instead of curbs and gutters

    Vegetated swales help water soak back into the ground.
    Roadside gutters collect runoff and direct it into storm sewers, streams or rivers. Vegetated drainage swales are often a better solution. Runoff collected from paved areas has a chance to soak into the ground and recharge underground aquifers. Soil and vegetation also strain out some contaminants. In some instances, monitoring wells may be needed to ensure that pollutants aren't reaching groundwater.

    Consider environmentally friendly erosion control measures

    In some instances, simpler approaches work just as well.
    Conventional erosion control measures include rip-rap, poured concrete structures, and extensive grading. New methods are emerging that use plantings and natural products to accomplish the same goals, sometimes even more effectively. Natural systems strengthen over time, while artificial systems tend to break down. More Earth-friendly erosion control includes planting willows and using biodegradable coconut-fiber mats to stabilize stream banks. Natural control measures, however, are not effective in all situations.

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