Under garden rooms / basements

Have you ever thought that you would like extra accommodation in your back garden but your garden was not big enough to accommodate it? How about having a room under your garden while keeping your garden privacy?

Project 1 – Underground garden room

This project was carried out in Lee SE12 London, part of the Greenwich Borough.


This basement / underground garden room was 6 meters away from the main property. The room was 5.5 meters x 10 meters in length and 2.4 meters in height inside.

The client wanted the room raised out of the ground by 600mm as part of the feature of a raised area that was there before. These pictures were carried out during the excavation of the cellar – basement. Over 650 tons of soil was removed and we hit shingle, clay and flint on the way down.


These are pictures of the steel work and drainage going in place. The drainage for the basement will drain to a main chamber and then be pumped to a soak away. The new basement / cellar floor is then pumped with concrete and a waterproof additive and left to set . The total thickness of the floor slab was 550mm. We used 12mm and 16 mm reinforcing bars and mesh. These were all linked together to create a heavy duty structural floor slab.


This is the first stage of shoring up for the basement walls. We used shuttering ply and 100mm x 50mm timbers for braising. We had to connect the new reinforcing steel work for the proposed walls to the floor slab steel work.The walls to the basement will be reinforced with metal and are 350mms thick, these to have a waterproof admix in. We then filled the shuttering up with concrete pumped from a ready mix lorry to form our first stage of walling.


These pictures are once the first stage shuttering has been removed and the walls have had time to cure. We are now ready to backfill the walls with shingle for drainage for the basement room.

Now for the second stage of the shuttering.

We connected our steel bars and grid work to the lower level / first stage of the wall. The walls to the basement have been shuttered up for the second stage of the concrete pour.


The shuttering has now been removed and all of the walls for the basement room have been formed. We have installed the light wells to the basement room and connected the drainage. We carried on backfilling the walls with shingle. This creates a type of French drain and allows water to run through the shingle to the drainage below.


Inside shot of the room once the roof has been pitched. The walls have not yet been tanked at this stage.General shot of works in progress and the start of the stairs being constructed leading to the garden basement room.

These are the final pictures of the underground room near completion.
We had installed a fibreglass roof system on the roof ready for the artificial grass roof. The ceilings have been fully insulated. The walls to the basement/ cellar have been fully tanked with sand and cement and a waterproof additive. Tanking a cellar or basement needs to be done correctly in a certain sequence or you will definitely have water problems.

Would you like an underground garage, room, office, studio, playroom or just like this client’s, somewhere to set up your own miniature train track?

Or these are great for recording studios, once constructed, as the sound proofing is excellent.

We can carry out full plans, structural calculations and building regulations for these underground projects.

When going underground use London and Kent Construction Ltd not a womble.

Project 2

Here are a couple of pictures of a room / basement we built under a back garden.

  • First we dug the foundations 3 meters deep by 600mm wide and poured concrete with a waterproof additive.
  • We let these foundations harden for 2 days.
  • Then we removed the soil from the inside of the footings to create a void for the cellar.
  • We then connected the reinforced mesh for the floor to the reinforced mesh at the bottom of the foundations and poured 300mm of concrete in to the bottom of the void to create the floor.
  • Once completing the floor we built a retaining wall to the basement to hold back the soil to the front.
  • We installed the steelwork for the ceiling and installed block work in between the steels.
  • We then concreted the roof area with a 250mm concrete fully reinforced and waterproofed.
  • We tanked the walls with a sika additive to keep water from coming through the walls of the basement.
  • After these works we built an extension on top.

This new build cellar was created in South East (SE) London.

As good builders carrying out underground basement rooms in the following areas SE2 Abbey Wood SE3 Blackheath SE4 Brockley SE5 Camberwell SE6 Catford SE7 Charlton SE8 Deptford SE9 Eltham SE10 Greenwich SE11 Kennington SE12 Lee SE13 Lewisham SE14 New Cross SE15 Peckham SE16 Rotherhithe SE17 Walworth SE18 Woolwich SE19 Norwood SE20 Anerley SE21 Dulwich SE22 East Dulwich SE23 Forest Hill SE24 Herne Hill SE25 South Norwood SE26 Sydenham SE27 West Norwood