How to Build a Rock Wall for Ferns
In building a rock wall, it is extremely difficult to obtain the perfectly natural appearance which is so desirable, and there is no doubt that tufa lends itself to such treatment better than any other rock. Quite a useful and natural cliff wall could be built up with fiat-bedded sandstone set at a gentle slope, and the general face diversified by an occasional bolder outcrop jutting out from the rest.
For stability, sound foundations of concrete below ground-level are essential if the whole structure is not to collapse through settling, and a few hidden dabs of concrete applied behind the rocks will help to keep things stable. The vertical cracks will provide the best planting places without endangering the structure, especially in the case of sandstones. If horizontal crevices ofare made, small stone should he placed between the rocks making the crevice, to support the upper rock safely, and such small stones should be set with cement mortar, taking care that the cement does not show. The rock building should be set to allow a gap about a foot wide between the rock and the wall for fern compost to be introduced.
Every three feet or so strong metal bars should be cemented into the wall and between the rocks to hold them securely. Bars with an L bend, with the short leg of the L set in the wall, are better than straight ones, or ‘butterflies’, made in the form of a double loop of extra-strong galvanized wire, may be used with the loop ends cemented into the wall and between stones.
The fern compost should be introduced as the building proceeds and it should be made quite firm every few inches to obviate as far as possible the inevitable settling. Provision for watering is best achieved by the use of irrigation hose along the top of the cliff.
It it is important that the wall should not get damp, before any building is attempted the whole wall should be thoroughly damp-wooled with waterproof concrete and in addition covered with polythene sheeting; the metal tie bars should be cemented into place before the sheeting is applied, and the sheeting made watertight where the bars come through, with a suitable polythene cement.
If the rock wall forms part of a neighbour’s boundary, he should be approached and his approval obtained in writing before starting the work. Should any damage be caused to a neighbour’s property through building such a cliff, relations might become strained, to put it mildly.
The size of rock should have some relation to the size of the house; a very large house would look well with outcrops of quite large rocks, if they could be got into place without demolishing the house; the deciding factor should be the provision of a congenial home for the ferns in a pleasant rock setting.
The question ofis not so critical under glass as the amount of water falling on the ground is under control, but if the house is low lying and there is possibility of much water getting in from outside, provision should be made for this to get away to a soakaway or other exit.