Raised Beds from New Sleepers

Following an accident I found myself permanently using a wheeled walking aid which has a seat facility.
While my gardening is now limited we decided that we should construct three raised beds from new sleepers. The internal size of these will be 120cm x 240cm x 40cm deep.
As we recently moved house, we have inherited a large number of pebbles (approx 8/10 cm) . My question with top-soil imported in tonne bags being a very expensive item, is could I cover the bottom of the beds with my pebles to a depth of say 8/10cm. This layer then to be covered with weed supressent fabric prior to topping up with imported top-soil?
What are thoughts regarding this layer causing the bed to dry out too quick?

 

Two beds would be general perennials and the third all Dahlias.
I do see it as an experimental the first year to see how it went.

 

Hi,

Thought it worth a post to ask if you are aware of the very high price of timber at the moment, new 2.4m sleepers from Wickes costing £60 each , if you can find any in stock as the supply across the timber trade is very hit and miss.

With the big bags of top soil and the weight of those sleeper assume you have got a small army of strong helpers ?

You can buy wooden, plastic and even metal raised bed kits, all a lot lighter than heavy sleepers and generally a lot cheaper.
eg - Raised Beds

Typically you would want to add some bags of compost / manure to your top soil, particularly if your soil is sandy.
As we found with our 30cm raised bed, things grow a lot faster, needing a lot more watering and attention, a bit of a catch 22 if you are looking to make things easier to manage, though a thoughtful planting scheme should help.

 

Timber has seen an increase in price, but it depends on who you are buying from.
The prices I have seen in the likes of B&Q and Wickes etc etc are over the top, it's gone up but not by that much.

If you go down the sleeper route, then a benchmark price you should be looking at for a 2400 x 200 x 100mm sleeper should be £25-30. For kiln dried, then you can add an extra £10+ per sleeper.

If your going to build three raised beds, then if you lay the sleepers on the side you will need 18 in total. If you lay them flat you will need double that. There are people who will deliver, these guys charge a flat £39 carriage fee.
Our Railway Sleepers - Yorkshire Sleeper Sawmill

If you went down the route of laying the sleepers on their side, it would cost £607 for the timber delivered from the link above. If you use the site in the above post, it would cost you more, plus the timber is only 35mm thick, scaffolding board timber.

 

Thanks so much to all contributors for the valued info to-date, much appreciated. I need to re-visit my sizes etc. regarding access from all sides and then proceed with ordering the materials.

I do think I shall be using all top-soil for the fill but leave it down a couple of inch from the top to allow for mulch.