I’m currently designing a single family home in Chicago of Masonry construction. The rear yard is about 24′ x 24′ between the new house and new garage, and is raised to about 4′ above grade. This is accomplised by pouring concrete walls w/reinforced masonry above for retaining walls. The general contractor has suggested using wood timbers and wood piles in place of the concrete walls and masonry for the retaining walls to save considerable cost. We looked into Uni-lock pavers, but did not discover much savings…
Does anyone have any experience or advice on using wood timbers for retaining walls up to 4′ tall? (considering normal soil conditions)
Thanks!
Replies
Keelah,
I've done a few of these with 6x6PT 4' OC with 2x12PT run horizontal. Looped 1/2" galvanized cable through the post 12" from the top back to concrete deadman postholes. French drain to daylight with rocks and filter fabric. I know my soil conditions and have P.E. friends. I have also done poured concrete and don't see that much difference in cost.
KK
KK,
Thanks for your reply, as usual cost is really the driving factor. I found something very similar to your description in Graphic Standards. Because we're building on the lot line, in the city of Chicago, we are technically not allowed to use wood construction. If I thought there were significant savings, we may be tempted to "mis-interperate" the code, but concrete may be the way to go after all.
thanks again! Keelah
Here in Minnesota wood walls last about ten years before they show failure they hold out for maybe fifteen before getting really bad.. Pressure treated or white oak the failure rate seems to be the same.. Some luck out and the soil behind the wood stabilizes and won't give any serious failure..
In Pittsburgh area, used railroad ties and stepped each individual tier back about 2 inches (stairs)with a half-lapped deadman about 4 ft long every 6-8 ft into bank behind wall. Staggered the joints in each tier so that all laps were at least 2 ft apart. Placed 4 inch perforated tile behind wall and run to daylight on each end. Covered tile with gardeners' fabric and backfill with gravel for about 2 ft at first tier and running to about 6 inches on highest tier. (In my case about 6 ft). Installed in 1968 and were still in-place and functioning as built in 2002.