Traditional Brick Bases

 

 

 

This is a rough guide to help you plan, budget and execute the Building of your traditional self build conservatory base. If you have no building experience it would be a good idea to have a look at the Durabase, insulated steel self build conservatory base system

The vast majority of conservatory base in the UK are built from concrete and brick. The alternatives are steel and timber bases but the traditional method is almost exclusively used in self build conservatory sector were the home owner wants to undertake the whole self build project themselves. If you have not had any brick laying experience, it would probably be best to employ a qualified brick layer or building contractor for your DIY conservatory project.

If you are a competent DIYer, then building your own base will save you a substantial amount of money. Before starting your DIY conservatory base you should have a good understanding of the process and what tools and material you will require. Practically all home owners want the floor level in the conservatory to be the same as that in the house. So all vertical measurements should use the DPC ( damp proof course) as the starting point. When deciding on what height you want the walls to be, don’t just select a random dimension, but calculate the wall height using brick courses. The most popular dwarf wall height is 600 mm above DPC or eight brick courses. This height allows for a very convenient window cill and still provides a panoramic view of the garden. It is however very popular to use a three quarter or full height wall to create privacy or place tall items of furniture.

The Process

Excavate Footings: If the site allows access for a mechanical digger, then this option should be considered even though it is more expensive than digging the trenches yourself. The time it would save and the ground conditions it can cope with will balance the expense at the end of the day. Keep in mind when the spoil comes out of the trench it will bulk up to two times it’s volume, especially in clay conditions. This should be taken into account when calculating the cost of the skips you will need to remove it from site. Remember when ordering skips that if you are wheel barrowing the spoil ask for a drop side as tipping becomes very difficult over the high sides. Do not retain clay spoil to use as infill as it expands and contracts when get wet or dries and that will make it structurally unsound. In average ground conditions a typical footing trench for a DIY conservatory will be about 600 mm deep and about 450 mm wide. These dimensions will vary dramatically in extreme ground conditions like clay, reclaimed land and high water tables. When you start the excavation and discovery these type of ground conditions it would be advisable to seek advise from a structural engineer or surveyor. It would be fool hardy to take a chance and in a short period of time have a crack in the floor that would cost you a lot more to repair that if you had paid for some advise.

Foundation Concrete: Remember, when laying out your footing to centre the walls on the width of the excavation. If you excavating in sandy soil and the trench wall collapses, it is best to shutter the collapse with timber or similar, or you will find your concrete budget will soar trying to fill these areas. It is important to pour all the concrete in one go. If you do it in two stages you will be left with a joint that is structurally unsound. The finished level of the concrete should be in exact brick courses below DPC. A 225 mm block is commonly used

Building off the Foundation: Prior to the brick laying starting a minimum of 100 mm, type 1 MOT (hardcore) should be compacted onto a level base. This is done before any bricks are layed to avoid to compactor loosening anything. This is also practical as it gives a firm base to work on. A foundation block can be used to start to bringing the brick work off the foundation. These blocks should only be used below NGL ( natural ground level) unless the walls are being rendered as they are unsightly. An engineering brick should be used to come out from ground level and should continue to DPC. Engineering bricks are much harder than common bricks. Ounce the brick work is up to DPC it should be allowed to harden (or go off). The areas around the perimeter should then be back filled with MOT and carefully compacted by hand. At this stage you will have a fairly flat, level area on which you need to brush a thin layer of sharp sand. It is good practice to wet the sand ounce you have leveled it to ensure it fills all the voids in the hardcore and gives a smooth level surface on which to place the underfloor insulation. The insulation should be a minimum of 50 mm thick, but a 100 mm is preferable as it will achieve a higher insulation value. The entry level insulation is compacted polystyrene (Jablite) but by using a more advanced insulation material like Kingspan or Cellotex, the U-value or ability to retain heat is much improved. The insulation sheets are normally available in sizes of 1200 mm x 2400 mm. They need to be close packed and cut to size being careful to avoid leaving gaps. It is good practice to seal the joints with tape.

Concrete slab and walls: At this stage the top of the insulation should be about 100mm below DPC if you are using a self leveling compound as the concrete finish or 150 mm below DPC if you are going to cement screed the floor. If you are a very talented individual, it is possible to float the concrete to a finish acceptable to take tiles or laminate flooring. If you are going to use under floor heating, height allowances must be made. Before the concrete is poured a continuous damp proof membrane needs to be placed over the layer of insulation and up over the brick which is the DPC level. It is always good practice to include a layer of reinforcing mesh into the concrete slab or oversite. The mesh should be sat on a number of 50mm concrete blocks to ensure that it is situated in the middle of the concrete slab. The concrete can be mixed by hand but most commonly readymix concrete is used for it’s convenience. When ordering the concrete you need to specify what it will be used for and how long you will need to offload it. The slab should be poured in one go and if you are using reinforcing mesh a mechanical vibrator should be used to ensure the concrete settles around and under the mesh, without any voids. Once the slab has gone off a 100 mm wide damp proof membrane is layed under the outer brick course to prevent any damp rising. Then the outer brick course is brought up to it’s required height. It is good practice to include tie wires, at about five per m2, to tie in the inner brick skin. A minimum of 50 mm should left between the brick skin to take a layer of insulation, Jablite as minimum specification but Rockwool will make the conservatory more energy efficient.

Project Conservatory Limited – Company Number: 7298972. “The Office” 23 Brereton Drive, Nantwich, Cheshire CW5 6HE.