I have an existing patio adjacent to the back of the house. I really want to expland the patio but I am concerned about covering up the roots for an extablished vine maple (~15' Tall x 15' Wide). The patio extension would be on the south side, which is the downhill side of the tree. I envision the uphill edge of the extension to be about 6" from the base of the rock wall which is about 5' from the trunk. As the picture shows, from the existing patio there is a 3-4" step down to a row of bricks and the grass which then tapers down the hill. Because the grade slopes down away from the tree I don't think that the excavation process will cause issues with the roots. I am more concerced about covering the roots with ~150 square feet of concrete. For what it is worth, I don't water the tree during the summer. I have thought about a low deck instead, but I like the idea of concrete to better match the existing surface and for the low maintenance. Of course the best way to match the old surface, fine grain surface, to the new will be challenging. How concerned should I be? Thanks!
No replies yet. Perhaps the people who can answer my question are busy out in the garden! I do have a few more questions related to my project. Would a paver patio be a better choice since it would allow some moisture and air to get through? If the general thought is that this patio extension won't be an issue, is there a preferred time of year to do this project to minimize risk to the tree? Thank you.
I'd use pavers or cobblestone since you're going over roots, and you want those to be able to breathe and drink. It also means that you can periodically re-level the area - if the tree keeps growing, the roots will eventually cause heaving. With smaller units (ie pavers) you can just take up the area that needs levelling. Personally, I'd start by covering the whole area to be paved with sand/gravel to bring the level up to above the top of the root surface, then pack it gently. Hard packing (ie with a mechanical tamping machine) could hurt the roots you're trying to avoid. Then soft-lay the pavers using sand instead of mortar. Another option entirely is to build a low wooden structure to clear the roots, then pour your cement or set your pavers into that. This way you are clear of the roots entirely, causing them no further damage and allowing breathing and water room, and you have the easy-maintenance of cement for the decking extension. This is a fairly common practice here in Ecuador, where both roots and drainage in the wet season are an issue. If you're really concerned about matching finish, try asking around the local tile suppliers for their broken/discard tiles, and scatter-mosaic the surface of both your old and new patio. This is even easier to maintain than bare concrete, and adds some visual interest to the surface. There are entire sidewalks (tens of blocks long) here done in this finish, and while the regular concrete has heaved and buckled, they're still lovely and new-looking. When I asked a resident how long they'd been that way, he said 20 years. You can also do this with fragments of granite or marble that were originally intended for flooring or countertops, if you're concerned about maintaining the more rustic appearance that the fieldstone bedwalls give you. I'm not sure about sourcing that materiel in Seattle, but here I'd just go to the quarry and ask around.
Sorry, I didn't see your query earlier. If you are determined to leave the tree where it is, I agree with using pavers... in fact, I prefer pavers anyway because I hate the permanence of concrete - so difficult to remove and dispose of if you or a future owner ever change your mind about where it is. Paver surfaces are a little tougher to care for as weeds can get in, but the permeability, flexibility, and repairability more than make up for that in my mind. But having said that, I have an unpopular attitude toward trees, which is that trees can be replaced. It is evident, in fact, that the vine maple IS a replacement tree already for a larger tree, probably a conifer, that became overwhelming to live with and work around. There may come a time when the vine maple too is too big for the space or its roots too invasive, and it will have to be removed and replaced. That being the case, in your position I would ask yourself what is your ideal patio design in the event the maple either has to be removed or succumbs to the building process (though it probably won't). It is quite possible that the tree is in an excellent spot where a tree of some sort will always be wanted for shade or privacy, in which case you will design the patio around it anyway. But if your ideal patio shape would change if the tree were gone, I would remove the tree now, build the patio you want, and replant a tree where you really do want one. Nice rock work, by the way!
Thanks for the feedback Lorax & Karin. The permanence of concrete does bother me a bit, though a jackhammer could take care of that. And there are local companies who grind down concrete for reuse as base material for roads, etc. At our previous home I built a paver patio for that reason, as well as it being something that I could do by myself more easily. I think that concrete or pavers is more cost effective than a deck and not needing to refinish a deck every few years would be nice. I haven't researched wood/recycled plastic decking material. There have been so many issues with various composite siding materials that using something new makes me nervous. If I went with the low deck option, made of wood, I am guessing I would need a vapor barrier over the ground under the deck to reduce moisture which could accelerate rotting. If that is true then moisture wouldn't be able to go through to the roots as well. Hmmm. I'll need to think about how attached I am to this tree. There is also another vine maple to the north of it which might suffer if the one close to the patio is taken down... due to more sun exposure than it is has had to deal with. Karin, thanks for the rock work comment. 43 tons all hauled by wheelbarrow to the back and upper side yard. All done for now, though I'll need about 5 more tons to terrace the ground below the patio extension. I need to post some pictures one of these days. Before we had a bunch of problem areas: a steep and weedy eroding slope, thirsty grass on a south facing slope, no level area for a vegetable garden, etc. So much easier to maintain now, even with the 4x increase in amount of planting beds to weed (good mulch is key!).
If you go with the low wood deck, try to find something like Eucalyptus wood, which is more rot resistant than, say, pine.
