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Question DetailsAsked on 5/14/2013

gaps in interlocking cinder block wall fence

A tree was planted within six inches of the wall. The wall, in front of the fence, has been repaired. Another section 12 feet from the tree is separating and leaning. Can the wall be repaired or does it need replacing? I am purchasing this home and need to know what to ask the owners for in repairs.
Will the tree continue to be an issue? It is a 30 foot Sumac. Should it go?

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You did not say how long the wall is. Hard to tell without seeing it, but I will give it a few thoughts for you to consider:

1) A sumac is not commonly considered an ornamental tree - to most people it is an invasive shrub, and a lot of people with hay fever are allergic to them. You also need to check it is not the type that is poisonous to the skin - m,any species have oils in them that severely affect some allergic and most asthmatic persons both from air dispersion of the oil, and ESPECIALLY if you rake up and burn the leaves, or burn branches in the fireplace or burn pit. Burning almost any sumac will affect a high percentage of people, including your neighbors.

2) Being that close to the wall means one or the other goes - either you take out the sumac and its roots, or the wall goes over as the roots spread - and they spread 50 or more feet from the base - commonly twice or more the crown width, and very close to the surface (commonly visible for 10 feet or more from the base). They spread by rhizome, like lupine and beans - so every place a root is cut (and every 3-12 inches along an intact root) it will put out new suckers that will grow into plants if you do not remove the roots too. The biology of the plant is such that it does not generally (unless damaged) sprout under its crown, but will sprout beyond that point and form new plants very aggressively - look at the sumac growth in the California Coast Range / Santa Monica Mountains that feed the famous LA and Ventura County brush fires - hillsides of almost nothing but massive sumac. There may be a root poison you can drill into the root stumps with and inject plant killer through, if you do not have small kids or digging dogs.

3) Joint cracks up to maybe the width of a pencil in a CMU (concrete masonry unit) block wall can be repaired. If it has physical separation for its full height or is visibly leaning more than 1% (1/8 inch per foot, or 1 inch out of plumb for an 8 foot wall), those sections and at least 3 feet each side of the affected zone should be rebuilt. Frequently a significant portion of the blocks can be salvaged unless they built it right and grouted rebar in the cavities (as required by code in most areas).

3) A lot of landscapers just stack the blocks and use little or no grout and no rebar, despite code. If it is over 30 inches high (or code in your area) and does not have grouted rebar per code, this might give you an excuse to demand rebuilding it to code.

4) Minor cracks and separation due to roots is normal - that is why you should not plant any types of shrubs or spreading-root bushes (anything other than flowers or vegetables) within 3 feet or so of foundations or walls, and trees and large shrubs should not be planted within 15 feet or more (more for major shallow rooters like sycamore, oak, willow and cypress). If you cut the sumac down and cut and REMOVE or poison the roots (they will resprout if not removed or killed), then cracks up to about 1/4 inch can be repaired without complete removal to footer level.

5) If it is leaning more than 1% locally or the entire wall is visibly leaning or has large cracks, or is breaking through the blocks (rather than along grout lines) then rebuilding of at least the damaged section is necessary. Also, leaning, unless right over a major root and obviously caused by the root lifting the footer and wall, may well be an indication that the wall was built without a reinforced concrete footer and rebar longitudinally and up into the wall - which would make it what is sometimes called a humpty dumpty block wall - ready to fall over at the least push. You should be able to see if it has a concrete footing under the blocks, though you might have to dig down 6-12 inches to see it. Depending on soil type and wall height and whether or not the ground surface is the same on both sides, the footer should protrude anywhere from 6 inches to 3 feet beyond the wall face.

6) Talk to your Realtor about what he/she thinks is reasonable to ask for (asking for complete rebuild could be a deal-killer for the seller), and get an opinion and a repair/ replace bid (with at least 10% contingency built in) from a mason so you at least can show prove much it will cost if you ask it to be repaired, or if you ask for a price adjustment to accept it as-is. Be sure the mason checks if it has a concrete footer of adequate depth (typically 8-12 inch thick reinforced concrete strip under the wall, about 2-4 feet wide).

7) One possibility, if you are not attached to the wall, is to buy it as-is and have a grand wall destruction house-warming party with some energetic friends using hammers and chisels, reusing the salvageable blocks as dry-fit planters and paths. However, it may leave you with a pile of broken block to cart off, and you would have to cut the vertical rebar comingout of the footer (or utilize it to start a trellis).

8) By the way - if you are in a grass or brush fire area, having a sumac within about 50 feet of the house (200 feet if part of a brushy area, and various area by fire code in fire-prone areas) is very dangerous - they go up like gasoline torches in brush fires because of the heavy oil content, as well as throwing burning oily leaves in the fire wind.

Answered 6 years ago by LCD

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