Since the base of your conservatory is the only thing that is going to bear the full weight of the finished structure, it is vitally important to get it right! This is not difficult but does require some thought first. There are several things to work out before you even cut the first sod. In this blog, we will look at what needs to be taken into account when designing and building the basework.
Firstly, what kind of conservatory are you going to have? There are three types; full height, full height panel and the most popular, the dwarf wall. Lets take the full height and panel options first, as both of these can use the same kind of base. The exact specification for the base slab depends a lot on what kind of ground you have. In this case we will assume that your base is going onto something like London clay, as we seem to sell a lot of our conservatories in and around London.
Mark out an area slightly larger than the external size of the finished conservatory. 150mm should be enough in most cases unless you also want a solid walkway around the conservatory in which case, allow the extra for that. Next you need to dig the whole area out to a depth of at least nine inches. A foot would be better. The hole then needs filling with hardcore and leveling to allow a good five to six inches of concrete on top to bring the raft flush with the ground. If you have access to a wakaplate to compact the hardcore, so much the better. When the hardcore is firmed down, lay steel reinforcing rods in a lattice across the base and fill the whole thing up with concrete. Skim the concrete to get as smooth a surface as you can. Leave it for a week.
The system for a dwarf wall is different. As we work on a 600mm dwarf wall for our conservatories, you need to go at least that deep below ground level to ensure a decent foundation. In the bottom of your trench you need to put a row of concrete common blocks firmed down and on top of these goes a trench block. From this the dwarf wall is built up with bricks to the finished floor height and the damp proof membrane sits atop this course of bricks.
Again, leave the blockwork and brickwork plenty of time to dry out before erecting the conservatory on your new base. A couple of other things to note; if the garden slopes away from the house, allow the extra depth at the lowest point to still give a 600mm footing. If on the other hand, the garden slopes towards the conservatory, it will be a good idea to allow a walkway and build a retaining wall to prevent the garden slipping towards the conservatory in very wet weather.