Landscaping, Patios, Decks - page 1


Q. I have a 1m x 3m x 0.75m trench at the bottom of my heavy clay garden that I want to fill to make into a raised bed (to help with the drainage). I'm going to have to buy soil/compost to fill the hole so do you have any suggestions as to the recipe and quantities I should use?

A.  It depends partly on what soil or compost is available and in what quantities, also on what will be planted in the bed. If you have heavy clay soil, then there is a chance that soil that is available locally and sold as top soil may also have quite a high clay content, so try to make sure top soil that you buy is a good quality loamy soil. Ideally, I would add top soil and good well rotted garden compost in the ratio of about 4 + 1.

Ironically raised beds need something in them to retain moisture, the idea being that there is plenty available but allowing excess to drain freely away. Organic matter fulfils this role while also adding nutrients. If garden compost in large quantities is not available, then use well rotted farmyard manure instead.

The organic matter will rot away in time and so the level of the bed will fall (slowly), just add more to the top as a mulch every now and then - annually say. Once the bed is in place and filled, you shouldn't need to dig it ever again.

This recipe is a general one assuming that vegetables or ornamentals are to be planted. If you are to use it for alpines, then add coarse sand or fine gravel to the mix, if acid - loving plants, then use peat as the organic matter or fill the bed with an ericaceous compost

addendum Q. Do you think I should put some bricks/gravel etc in the bottom of the trench to help with drainage?

addendum A. As I understand it, you have a trench that you intend to fill and then extend above ground level using a retaining wall of some description. I wouldn't add any extra drainage unless you intend to fill it with plants that particularly require it, alpines / Mediterranean plants etc. There is the danger in a heavy waterlogged soil that such a move could actually give you an underground sump as the water from the surrounding soil drains into the gravel / brick area. For the vast majority of purposes, being above ground level will supply the extra drainage required.


Q.  I have a 6m by 4m area which I want to cover with gravel, before putting decking, tubs etc. on it, but although I have found some local gravel suppliers, I can't find anything to help me calculate how much I need.

A.  It depends on whether the area is trafficked or not i.e. walked on. If you work on the basis of 1 tonne per 10 square metres, this will give you a good covering. Bear in mind that it will add depth to the area and so the area will need to be dug out relative to the surroundings or a barrier will need to be put in place to stop the gravel from spilling.

You could use log roll, (though I'm not keen on it), or rough fencing posts laid horizontal with the pointed end cut off. Make sure you peg them in place securely if you go for either of these with substantial wooden pegs driven at least 6" into the ground, I use pegs 12" long in total for this. Drill (3mm diameter) the top of the peg to take the nail, it is very likely to split being so close to the edge of the wood otherwise.

If you are going to cover it with decking, I'd use landscaping fabric with just a scattering of gravel to stop the wind from lifting it. You could get away with half this amount or less if it is all to be covered.


Q.  I am wanting to plant up a railway embankment which serves as my back garden" and measures about 40 ft wide by 50ft tall and is on an incline of about 45 deg.

Can you recommend where I can source plants at reasonable price as I obviously need a lot - the whole area was cleared of scrub during the summer but I did nothing with it till now because of the severe drought.

Conditions to plant are now as good as they are going to get although the underlying "soil" is a type of scree which one would expect a railway embankment to have been made up from. I am conscious that if I put compost down or topsoil it may just wash down the slope and I am keen to do something with it to pretty it up in time for next spring.

A. When it comes to planting, I'd make large holes as deep as you have the energy and fill it with plenty of organic matter. Mediterranean plants should do well if it's well drained. This way the plant roots will be encouraged to go downwards rather than sideways. As you say adding to the surface may result in topsoil ending up at the bottom, so aim for enriched pockets rather than a veneer.

Where to buy plants? If you want a lot of plants - say £300+ worth at garden centre prices, you should be able to get them wholesale from a nursery nearby for 1/3 to 1/2 of that amount. There's usually a minimum spend of around £100 ex. VAT and you help yourself with no advice available, often no labels too, other than a Latin name, so you need to know what you're looking at. You may be able to ask for a plant list to peruse before you go and then email your order - depends on what level of service they give - more service, higher prices, many nurseries will expect at least 5 of any one type unless you get the plants yourself - best to ask first. You can get trees and some shrubs bare rooted in the winter months when they will be much cheaper. Many perennials are also available bare rooted in the winter when they can be bought mail order if not available locally.


Q. I have a sloping rectangular garden, I have recently excavated an L shape to form a raised garden in one L and a patio in the other "L". I need to retain the higher level but want to do it as cheaply as possible. can I do this with planks and posts? the retaining partition will be Z shaped (dividing two "L" shapes) how is the best way to do this?

A. It depends on how deep the partition is and how long it is. Railway sleepers are a good way of doing this. They need to be bedded well, on a foundation of compacted hardcore or shingle if possible. I'd ensure that they remained upright with posts hammered into the ground and screwed to the sleepers with long screws. These can be hidden from sight and buried. Make sure you use tannalised timber for the posts you knock in. Sleepers are difficult to cut if you need to trim them, requiring a chain saw - even then it is an effort.

A more convenient alternative is to use 2" thick tannalised timber available in 4" or 6" widths. This is easier to cut than sleepers, but not so substantial. It can be painted or stained afterwards to blend in or provide a contrast.

As another alternative you could use rough fencing posts laid on end with the points cut off, in fact if you have a fencing supplier nearby a wander around the wood yard may give a few ideas of types of timber you could use for the more rustic look.

All of this assumes that there is no more than 12" / 30cm of soil to be retained, if it is greater than this, you really need a good foundation and substantial upright supports.


Q.  I have just had a tarmac drive laid on top of my front garden it is sinking and weeds are growing through the contractor said put weed killer on it does this harm tarmac?

A.   Any drive way needs digging out and at least 4 inches of compacted hardcore laying before being tarmacced. Weedkiller is irrelevant as they couldn't get through that for a very long time. It certainly shouldn't sink either. I'm afraid to say it sounds like a cowboy job.


Q.  I have some left over oak flooring & would like to use it on my front porch. It is a covered porch, but the wood will be exposed to the elements including rain & snow. Is there any way to seal the flooring to minimize shrinking, expanding & other unforeseen problems. It there a good time of year to install the flooring. What other unforeseen problems might I be facing?

A.  This is not something I would attempt with flooring that is meant for indoors. Much flooring is laminate rather than solid, so the layers will just separate when they get wet. Even if it is solid, it will probably be too thin to stand conditions outdoors as flooring. Sealing and preserving should not pose too much of a problem, warping in constant moisture (like in the winter months where the boards may not dry out properly for weeks) is the greatest problem. If the flooring is laid as in the house in tongue and groove, then moisture will become trapped in between the surfaces where they touch, the wood will dry differentially and the boards will warp over time (probably not much time at that). Of course it is possible to have a solid wooden floor that faces the elements, on boats for instance, but the wood is much more substantial and can resist warping.

These problems could be overcome by laying the boards as decking, over a sub-base and with gaps between the boards so providing ventilation for drying out. You would however have the problem that the boards are not thick enough to be able to support themselves properly needing very short runs between supports and also probably needing the tongue and groove planing off.

For wooden flooring outdoors, you need to use decking boards with a suitable sub-base, that are of a good thickness.


Q.  I have recently finished converting a Dutch barn into a house, and all the land needs to be turned from cow sheds, tractor sheds etc into a garden. Firstly I would like to plant a hedge that will attract as much wildlife as possible i.e. birds, insects, mice and anything else that needs to be protected from the elements and fed. Also I would like to plant a lawn, unfortunately the lawn is BIG, is there a grass seed that will grow SLOWLY? And finally, there is a very long and ugly wall that I would like to cover with the most attractive and fragrant climber I can find, I would like ideally to plant a mixture of Ivies again to attract wildlife. Any suggestions and ideas would be gratefully accepted.

A.  Hedge - the most wildlife friendly hedge will be a traditional mixed hedge of native species. I suggest you get in touch with a local countryside organization as I'm sure they'll be able to get you in touch with a local supplier and now is a good time to plant.

Lawn - slow growing grass seed? 'fraid not - despite claims of seed coming to market soon, it hasn't happened in the last 20 years and I don't think it's imminent. Some grasses are referred to as "slow-growing" but that's only because they'll grow in shady conditions, it's the shade that slows them down. You'll just need to get a bigger mower so it doesn't take so long to cut, also consider having a wild-flower meadow area that is left to grow and only mown twice a year to reduce the work load.

Climbers - It depends on how much sun it gets, my favourite is the Wisteria, though the flowering season is short-lived. Ivy - again, like the hedge, native is best for wildlife. Ornamentals won't be as useful and if they are planted with the native, they'll lose out. If you have an outbuilding for it to climb over, honeysuckles are good and wonderfully fragrant too, they're not good on walls and are better in 3 dimensions, climbing roses are good if you place wires for them securely.


Q.    I am looking at building a retaining wall out of round timber posts laid vertically side by side. They will graduate in a s shaped curve down the garden from ground level to holding back a maximum of 1.5 feet of earth. Because of the curve I can't use beams horizontally between the posts and am therefore having a few problems deciding the best way to lay them as a concrete base will obviously not join all the way round each post.

A.  I don't see what the problem is with concrete? You'll need to get the whole thing prepared to do it in one go, or maybe a few stages. Dig a trench and fill it with concrete and then as you place each post in place, make sure you wiggle it around to settle the concrete around it. They will be surrounded apart from where they touch.

Another way - or maybe in addition to the concrete, as you'll need to keep all those fiddly posts in place while it sets - is to use a builders band screwed to each post using a treated screw. If it's below the soil level, you'll never see it. Lay it out as a strip so the posts help hold each other up. You could use two strips for extra strength.

With 18" of soil, you'll need to put the posts in about 6" minimum, the more the better. Make sure you use pressure treated posts and get a sealant for both ends before you start to position them. The secret here is to prepare everything fully in advance and then put it all together in one go rather than do it as you go along.


Q.    What is the best way to lay stepping stones once I have turfed the area running down my garden as I have removed the paving slabs there

A.    Drop (place) the paving stone where you want to put it and use a spade to cut around it. Remove the stone and remove the turf it covered. Dig down 2" + the depth of the stone and level the soil. Lay a 2" layer of builders sand, level as best you can and place the stone on top - it should be flush with the grass and stable. If it's not absolutely stable, then it will bed down after a couple of good soakings of rain.


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