Sunday, January 28, 2007

Roof Gardens and Weight Allowances

The design of your garden will depend completely on how much weight the roof structure can sustain. In older buildings, this is a real challenge. In new and renovated buildings, developers are aware that end users of a terrace space expect the amenities of rooftop living: including but not limited to: hot tubs, large containers to sustain specimen trees, pergolas, etc.

Not everyone is so lucky. Most rooftop gardeners will have to stay strictly within the weight limits of the building. If there are no such specifications, a structural engineer will have to be hired to determine the amount of weight the roof can support. In addition, the roofing contractor who installed the waterproof membrane that protects the building from water damage, has a specific set of requirements to ensure that the warranty provisions are not violated. The building management company may have this information available.

Landscape designers and related professionals will not undertake a project of any size without weight allowance information. The liability for damages can be enormous for everyone.

Having said all this, the weight of planters can be manipulated through various methods to lighten the load. Everything from lightweight planters to increasing drainage levels to manipulations of the soil mix. The general rule is to stay within 40 to 60 lbs per square foot. But this is just an average. Some buildings will specify a lesser weight amount. This includes the weight of the planter, the soil, and the plant. Some specifications calculate the amount of weight the entire roof can sustain, while others differentiate areas of the roof that can sustain heavier weights because of load bearing beams.

If you would like all the calculations to determine weights, please email me and I'll send them out to you.

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Great Resource:
Planter Resource in New York City
28th Street betw 6th & 7th Avenues
(closer to 7th)

Saturday, January 27, 2007

Cleaning Concrete Pavers

Concrete pavers are routinely specified for roofdecks, terraces and backyards. While they are long-lasting and relatively cost effective, they are also porous and require maintenance. Rust, grease, wine, white residue, dirt/soot, and mold stains on your pavers will ruin the look of your garden space. (Photo above shows pavers being installed.)

Some professionals recommend sealing the pavers to reduce dirt & grease absorption. We have never found a sealer that lasts longer than a year, in spite of claims by various manufacturers. Application and re-application can become very expensive (depending on the size of your roof area -- between $1500 to $2500 + per application).

We have also tried many cleaning products costing from $20 to $200+ but have never found a product better than baking soda and a mild solution of bleach.

Concrete pavers come in many colors and are made by adding pigment to the concrete mix during manufacturing. This means that the color runs thru the entire paver and is unlikely to lose color during cleaning. **But please do a test cleaning on a paver before you do your entire roof surface.

What you will need:
5 gallon bucket of water with 1/2 cup of bleach
Baking soda
Long handled stiff bristled plastic scrub brush (do not use a metal brush).

Sprinkle a liberal amount of baking soda onto pavers;
dip brush in bleach solution and scrub in 8' x 8' sections; allow to sit on entire surface area for a few minutes, then rinse thoroughly. Although you can definitely spot clean a paver, it is better to clean the entire roof surface -- or large areas at a time -- to avoid variation of look from section to section.

To avoid bleach splashing onto your pots & planters, place a large (opened) cardboard box upright against each planter. Scrub/rinse, re-place the cardboard against next planter.

For your information: The rust is caused by the iron oxide minerals in the paver combined with water -- and the metal railings, furniture and fixtures in your garden. The white residue, called efflorescence, is the lime released within the concrete carried by water to the surface of the paver.

Never use acid cleaners on your pavers.

Clean grease stains immediately. Wipe off excess oil; apply detergent and allow it to sit for 10 minutes; then wash with hot water. If there is still a stain, scrub with bleach and baking soda. Never use amonia and bleach together; the fumes caused by this combination are dangerous to inhale.

Do not use this cleaning method on granite, marble, or other natural stone products. These products can be fragile and require a professional stone cleaner or restorer.

NEXT POST: Roof gardens and weight allowances
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Friday, January 26, 2007

NYC Roof Gardens in Winter

Winter Gardens

NYC: Unbelievable cold today (9 degrees with face numbing windchill). Tomorrow the forecast is 40 and warmer on Sunday. It's been an incredibly mild winter in most of the Northeast (except for today) -- but not much rain since winter began.
In times of mild weather and little rain, containers can dry out. Last February and March, for instance, the temperatures were mild but only a few inches of rain. We lost two large Cryptomeria trees (See photo above; tree on left/center is the Cryptomeria) -- not because of severe cold -- the reason usually cited for Cryptomeria death -- but because of lack of water in late winter/early spring. Since irrigation systems are not turned on until all danger of frost is over, most container gardens -- and even some inground ones -- may require hand watering when temperatures are mild and there isn't much precipitation. When it's supposed to be winter ... frozen; dormant ... but it's not really.

Use the "finger test" to determine if you do need to water. If the surface soil to 2" is dry, water deeply, until the water runs out of the bottom of the container. Avoid sprinkling or spraying the soil. Roots gravitate toward water (and oxygen) and if water penetrates to only within a few inches of the surface, you'll have roots growing up -- and not down and out, the way they are supposed to grow. Always water deeply with an open hose (remove the nozzle). To make certain the water is penetrating all part of the container or if the soil is very dry, water once thoroughly and then repeat.

Next Post: How to clean cement pavers
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Great Garden Resources:
Trellis Structures in E. Templeton, MA
Beautifully made arbors, pergolas, and trellises at reasonable prices.
They ship most items, but will deliver to the city on larger and custom

Bottega Furniture in Dayton, OH
Handmade outdoor furniture made of Ipe; unusual design, elegant,
but sturdy. Met thm at the NYC Home&Garden show a few years
ago. Wonderful stuff.