Planning the build
Why build an extension?
Initial design sketches
On-line Building Regs
Meeting planners
 Meeting building control
 Planning the foundations
 Planning the floor slab
 Marking out the footings
 Damp proof course issues
 Possible drainage problems?

 Construction of the walls
 Proposed roof structure
Windows diary
 Window challenges
 Initial window plans
 Making the casements
 Making the frame
 Designing leaded lights
 Making leaded lights
 Assembling the window
 The little window

 The door frame
Demolition diary
 The demolition starts!
 The demolition continues
 Still more demolition

Foundations diary
 Foundation issues
 Drain issues
 Digging the foundations
 Rethinking foundations!
 Pouring the foundations

Floor slab diary
 Rethinking the slab!
 Floor vent extensions
 Preparing the slab #1
 Preparing the slab #2
 Pouring the slab

Walls diary
 Preparing to build walls
 Build up to the DPC
 Build the walls #1
 Build the walls #2
 The gas men cometh
 Build the walls #3
 Finishing the walls
Roof diary
 Roof structure build
 Tiling the roof
 Finishing the roof
 Finishing the gables
 Roof insulation

 Floor screed
 Shower room
 Shower room floors
 Shower room walls
 Utility room
 Utility room walls
 Utility room floor
 Finishing the windows

Project finished!
 Final inspection
 The certificate
 Final thoughts

 Twelve months on!
 Material costs
Sister sites
 House re-roof project
 Home gas usage data

 Stop paint flaking
 DIY secondary glazing


Getting ready to pour the slab #1

Friday, 20th April: There are a number of things that have to be done before pouring the slab. The next inspection is Stage 4: Oversite filling i.e. the slab mesh in place.

Mains water feed: I need to cut off the 1/2 inch BSP water pipe and connect it to standard 22mm copper pipe.

The first task is to turn the mains water supply off on the pavement outside of the house with a specially bought 4 foot long stop-cock spanner.
Using an angle grinder with a metal blade I cut the pipe off.
I used a special compression adaptor bought from the local plumbing shop to convert it to 22mm pipe. The adaptor is made by: George Fischer Piping Systems.


I brought the mains water pipe straight up using a plastic pipe to protect the 22mm copper pipe as it passes through the 150 concrete slab.

No leaks!


Saturday, 21st April: I filled in the foundation trench within the wall with soil and rubble stamping it down as I went.

When ready the surface will be covered an inch of sand to ensure that the first DPC sheet is not punctured by rubble.

Notice I said "first" - The Building regulations Surveyor has said I should use two of three - more on this later.
It's really beginning to look like an extension now!
After a lot of thinking, I have decided to change the layout of the drains. The 40mm kitchen sink pipe now connects into the main house drain using an adaptor. This means I can do away with the external open drain. This is much tidier with the pipe eventually being covered by the step from the kitchen door.

The main drain will be taken through the 150mm slab but will be blocked underneath the screed so that it could be made available to use if so needed in the future.
I've also marked the bricks that need to be removed to key the slab into the wall using white paint. Taking out the vent in the middle of the wall showed me that the wall is solid and has no air gap. This will make it a little more difficult to remove bricks to a depth of 100mm as many of the bricks are laid lengthways across the width of the wall.

Inspection chamber cover:  As the drain inspection chamber is inside the extension a double sealed unit is required.

I ordered on-line a 450mm x 450mm doubled sealed and lockable cover from Manhole Covers Ltd. It's really nice to be able to on-line as many other building related product sites don't even list their retailers!

The part number was MHC-7123/DSL
 This picture shows how double seal works.
The cover only took two days to arrive after ordering it on-line from the supplier's web site.
Monday, 23rd April: This is the job that I was really not looking forward too!

However, I found that using a hired Kango masonry saw really made the job quite easy.

Remember, the wall was solid so I had to cut only half way through the wall!
I cut the first two slots in half an hour and I couldn't suppress my worries enough not to put bricks in the slots!

It only took me a couple of hours at the most to cut all five slots so it was a task that was much simpler than I actually thought.

Under floor-vent extensions: One of the issues I have to sort out before pouring the slab is extending two underfloor vents from the wall of the house, under the slab floor of the extension, and venting on the outside wall of the extension. One of these is shown below.

Clearly however this is achieved, it needs to go under the slab. If there is a problem, there is always a solution and products are available from the company below.

Timloc underfloor venting products This picture shows the telescopic underfloor ventilator that connects to the timloc air brick.

It sits between the inner and the outer wall and moves the vent to below the slab level.

There are other accessories and one I need is 1205 which enables the connection of the vent to a standard 100mm drain pipe that goes under the slab.

Another telescopic underfloor ventilator is then used to take the vent above the slab on the external wall and connect to the airbrick.

Clever stuff!


I bought the bits and pieces for extending the vents from Jewson.

Here is the first extension in place - the vent pipe goes under the slab.


Here is the second extension in place.

The old vent fell right where I needed to cut a slot out of the wall so I moved to a position between two slots.


Here are both vent extensions in place.

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