Tie Back and Crib.
There’s an advantage of building this wall which is well worth considering. That is if there is any unevenness of the ground then this particular design of wall can be built a lot easier than using a post and rail system.
Because the sleepers are stacked on their face and you are using the thickness of the sleeper 75 or 100mm (3” – 4”) for the face of the wall, this measurement is easier to deal with the ground than when the sleeper is sat up on its edge.
Always try and start where the ground is the lowest as you can build this wall in both directions from that point.
Just keep in mind to stick to the same levels with the rails and spacers, don’t step the next sleeper and alternate them, otherwise the top will also step up and down with each sleeper you lay in.
Now you first have to work out where the wall has to finish, not just in the height but the positioning as well. The wall is built with a minimum of a 25% batter so it moves into the fill quite rapidly as the wall increases in height.
So work down from your finished height using a level and measuring tape and if the wall has to be let’s say approx. 0.9m (3ft) high, and you will always want to finish with a rail on top NOT the spacers.
If you are using 100mm (4”) thick rails and 75mm (3”) spacers then for every 175mm (7”) rising you are battering back 50mm (2”) which gives you approx. 28.5% batter. Just so we can use the same template for the step in for each layer of rail and spacer.
So to start off you will need to measure down multiples of 175mm (7”) this will work out to be 5 sets of rails and spacers plus the bottom rail being cut into the ground 50mm (2”). This will land you at the exact height but as far as the positioning goes for each set you need to bring the base of the wall out 50mm (2”) and there are 5.5 sets so the bottom rail that is dug in the ground will need to be set out 250mm (10”) from vertical.
Also remember the width of the sleeper that is lying face down to your top position. So if this is critical then you will have to add this width to your step out measurement for an accurate base run. See Diagram 04
If you have to change direction along the length of the wall the cuts on the end of the sleeper rails should be shared angles so they butt together.
Step 1. Starting at the lowest ground level you can lay your first sleeper in even if it’s the only one or a half, this doesn’t matter. The spacers and ties are then placed on top of that fixed with gal flathead nails or similar, setting the ties back 25mm (1”) from the face. It is important to try and get ties in on this base run as it provides a good anchor. See Specifications. So when you are placing the rail on top of these spacers they are also stepped back the same amount, this giving us the batter that we need.
2. You do need to fix a spacer at the end of the rail regardless of whatever measurement it comes to, so you can adjust the distant measurement of how far apart the ties and spacers are but it looks better if they are all fixed at 1.2m (4ft) apart. So as soon as you can position them to one in the middle and one at each end of the rails, the better it will look.
3. The Ties should happen on every third row MAX, It does hurt to vary where they are fixed to as this will support different positions of the wall, just make sure that there is not a large portion of the wall that is secured. See Specifications.
4. Back filling with the gravel can be done as the wall is progressively being built, this is a lot easier than leaving it to when it is finished. You might just want to place some landscape fabric between the soil and the gravel to filter the dirt from creeping into the gravel. If you are and you intend to use the boards to control the thickness of the gravel then you will need to place this material underneath the gravel at the bottom. This will prevent the board from pulling the material up and out, also pull the board up fairly frequent so there is not a lot of weight against it. Back filling becomes so much easier when you just place gravel on the wall side of the board and dirt on the other.
5. So it’s just a matter of repeating the process of fixing the rails to the spacers / ties stepping them back each time and then fixing a row of the spacers.
If all your prep work, measurement and calculations were done properly then you will end up with a great wall you can be proud of that will last a long time.
The Crib Retaining Wall.
Although the wall has very similar looks to the Tieback, the difference with the crib is that it’s made up like a box section, fixed together and filled with usually larger gravel 50 – 75mm, (2 – 3”). All the pieces are prefabricated and they all just lock into each other, this enables it to be built very quickly.
The base preparation is usually a Road Base footing or if it’s very high it will be a concreted one, and this will vary in size along with the wall as to how high the wall is.
Because this wall is mainly used when it’s higher than 1.8m (6ft) then engineers and council are usually involved. Each will have their preference on how it is to be built so I’m not going to digress too much on the procedure.
You will need to consult with an Engineer if you want or need to use this style of wall.
This wall is also prefabbed in concrete as well, although these are generally used for the sides of roads or for very high applications.
Now pop on over and see what I have to say about Ted… Just CLICK the picture below,