construction note no.6004
| subject: | railway sleeper retaining walls (used vertically) |
| relating to design note nos: |
1073: vertical space; 2073: changes of level 3073: terraced walls & steps; 3074: terracing with decks |
As of June 2003, A new EC directive means it is illegal to use railway sleepers, or any creosote impregnated timbers under certain circumstances. Whilst this should not prevent most domestic use, please click here for more information.
fig. one. Easier than digging by hand...
fig. two. If working with curves, keep stepping back to get the overall picture - or you'll have to live with an “off” curve!
fig. three. Close-up showing how sleepers are placed in batches of three or four.
As we have seen in the above design notes, railway sleepers (railroad ties in USA) make an ideal material for constructing walls and terraces.
Cheaper to buy and quicker to construct than brick or block walls, they will form a solid and lasting solution to all terracing needs.
There are two main ways to use them, either vertically, (see fig. one) or horizontally. The former is ideal when creating curved walls but is more labour intensive due to 33% of the sleeper being buried. The latter is good for straight walling runs which lay upon a simple strip footing - walls can also be built to a greater height in this manner, although for very tall retaining walls I would recommend a proprietary inter-locking retaining wall system.
Railways sleepers used vertically can create curved retaining walls but are limited in height to about 1.6m/5'6”
construction method when used vertically:
fig. four. Don't let the sleepers spread out at the base as you lay them! use a spirit level to keep them vertical.
fig. five. Even if they are vertical when you set them in, if you back-fill before the concrete has really set (72 hours +) you might push them forward. use tie-backs.
fig. six. Close-up showing how sleepers are wired together just below the soil level.
- Excavate a trench to a depth equivalent to 50% of wall height, 600mm wide.
- Try to work wall heights to a maximum of 800mm to minimise wastage ie. use ½ sleeper lengths.
- Cut sleepers to length required (hire a qualified chainsaw operator).
- Place 3 or 4 sleepers (as many as one person can manage to hold in place) to centre of trench, cut end down, butted up close to previous sleeper. Keep top heights slightly uneven.
- Ensure sleepers are vertical to front and side faces. Note that walling cannot be battered back from the vertical when working in curves (unless hired operator is very nifty with chainsaw!).
- Place concrete mix to either side of sleepers - mix up to 20% rubble in if available.
- Wedge end sleeper with lengths of batten whilst preparing the next batch.
- Once concrete has set, (minimum 48 hours) wire backs of sleepers together using 3mm galvanised wire and 30mm fencing staples. Do this just below the soil line.
- On long straight stretches, or walls over 900mm height, horizontal tie-backs may be needed into the bank.
- Gaps between sleepers act as drainage outlets.
- Backfill rear of trench with drainage medium (gravel).
- Place topsoil to top 300mm (over drainage medium), tread down firmly.
- Leave sleepers some 100mm above the soil level to allow for a mulch to be applied.
summary:
- plan terrace heights in sleeper lengths, or even divisions of, to minimise wastage
- bury 30% of sleeper in trench
- use bottom face of sleeper (indented with aggregate) as exposed face
- place a maximum of four (at ½ length) sleepers to trench at one time
- ensure they are vertical to front and side faces - knock the end one in at base
- once set (48 + hours) wire together along backs
- use tie-backs to bank on long stretches or tall walls
- after 72 hours, backfill with drainage medium and soil
Other construction notes which relate to this subject:
