Mid November update

A couple of things have moved on:

The wall plate I bolted to the parapet wall adjoining Jean's house was only a 4" x 2" timber held by half a dozen sleeve anchors and when I thought about it I decided that I needed something more substantial.  So I removed all the rafters and unbolted the wall-plate.  I cut a couple of lengths of 8" x 2" down to 6" x 2" and drilled it with about 20 bolts.

Once it was on I re-fitted the rafters using galvanised truss clips to locate and secure them.  The rafters are nailed to the ridge plate and spaced equally from the centre point with correct gaps for the 4 velux windows.  Now I need to cut a whole shed-load of noggins to keep the rafters straight and stop them from twisting.

The outside gable end of the extension needs some work to fit the fascia and soffit so I can build the box gulley and lay the roof membrane and battens.  Unfortunately i can't get scaffolding to that end because that is where all the sand/soil/rubble is piled up.  So the next job is to get a skip and clear the space outside the back wall for the scaffold.  The largest I could order to fill with building rubble is 8yd.  I don't think it will be big enough for all the waste, but at least it will clear enough space for the scaffold to move into position and get the roof moved on another stage.

I'm not keen on the short, dark evenings and cold, wet and windy weekends for working on the extension.  I think the chances of getting the roof covered by Christmas are getting slim.

Happy ever rafter

The rafters are 8" x 2" timbers, nominally 14' long (200mm x 50mm x 4200mm) which needed cutting to length and notching at each end to fit over the ridge beam and onto the wall plates.  I cut a piece of timber that had been nailed to the back wall of the house as the wall plate for the old conservatory to make the ridge plate on top of the steel ridge beam.  It needed cutting down from 6" to 4" but was clean and in good condition so it seemed a waste not to use it.


Each rafter needed to be mitred at the end to the 20 degree pitch and then notched to fit the exact distance between the ridge plate and the wall plate.  I started by using my mitre saw, but moving the rafters into position for each cut was difficult without having roller stands to slide them along, so I resorted to clamping them to a pair of trestles and using my old circular saw - which coped well with the 2" depth of cut.  I did have to finish each cut off with a hand saw so that the circular blade didn't over cut any of the lines and weaken the timbers.

At each of the gaps for the velux windows I needed to double the rafters to ensure sufficient strength to support the windows.  The wooden ridge plate and the two wall plates overhang the end wall of the extension so I can build in a 6" soffit overhang above the triangular gable end windows.

These pictures only show the rafters laid on the plates, not adjusted for position or trimmed to ensure they are straight, parallel or at right angles to the walls - all this will come later.

It is interesting to note how much more of a feel for the actual size of the finished room it is possible to get now there is a roof structure.  What would be useful at this point would be a second scaffold tower and/or some wheels for this one as it is difficult to drag and I will need to move it all over the extension to be able to get to every part of the roof structure.  I suppose if I can get a second one I could easily sell it afterwards...

The metalwork is in.

Question: How do you lift a quarter of a ton of steel seven feet up onto the wall?  What's more how do you get a 120kg steel beam twelve feet up and located in the hole in the house, bolted to a post at the other, and make sure it is both straight and level.

Answer:  You hire a Genie SL15 Super Lift with a boom.  it's a great piece of kit (about £3500 worth of great!) that makes the lifting part comparatively easy.  It is a hand-operated winch with extending rail that will take the load to 15 feet.  The hard part is manoeuvring it when it is hanging.  Quarter of a ton of steel, hung from some webbing, seven feet up, is not the easiest thing to place.  However, once the lintel was settled and the post was lightly attached - allowing plenty of adjustment - the ridge beam caused a few problems of its own.

I needed to be in three places at once: operating the lift, locating the bolts into the post, and pushing the end into the hole in the house wall - good job I have long arms and a scaffold tower.

I have to say that in all the moving and locating of the steel the most useful tool I have had has been my car trolley jack.  It will happily lift 2 tons and take the strain of the steelwork.  I used it on the ground to move it initially; then it was priceless up on the scaffold to lift the beam just a few mm to allow it to be slid into the wall.  I don't think I could have managed without it. 


The base of the lintel has had two coats of zinc oxide primer and will have a couple of coats of black gloss to protect it.  It is the only part of the steelwork that will see the light of day.  The ridge beam will be enclosed in the roof timbers, the top and sides of the lintel will be built on and the post will be enclosed in some way.

I'm not sure how to do the post yet.  It is on the inner leaf of the wall, so it would be perfectly possible to install a single window outside it, stretching from one side of the building to the other, however it may be better to build a 30cm wide pillar around the post to encase it and have two smaller, triangular windows instead.

Now the steel is in, the next job will be to attach the wall plates.  The one on the driveway side has been there for a while and is just awaiting the straps being drilled and screwed to the walls to hold it in place.


On the other side the 4" x 2" timber wall plate will be fixed by some 4" sleeve anchors drilled directly through the timber and tightened into the wall.  It is important that I get the wall plate absolutely level as the fall of the box gully depends on the roof being level.  Once this is on I can start cutting rafters and will have a fighting chance of having a roof on by Christmas.

It's a Steel

As the summer holiday ends and term starts there are only a couple of days' block laying left to do before I need to install the structural steelwork,

The combination of the architect's plans and the structural engineer's specifications are sufficient to obtain quotes from steel suppliers around Norwich. As this is an area in which I have no experience I could easily be taken for a ride in terms of price.  I mean, how much is a 6 metre steel lintel?  So I compiled a precis of the specifications and sent it by email to 4 companies to see how close their quotes would be.

Having spoken to one company I was reassured that the quote would be for an approximate length, but they would obviously require accurate measurements for the production.

Three pieces are required:  A lintel that runs almost the entire width of the extension above both the bifold doors and the kitchen window; a ridge beam that comes out from the house to the centre of the back wall, supported by the third piece, a 1.5m post.  All need drilling, welding plates attached and painting - so it's a bit more than just supplying three bits of metal!

I measured both pieces umpteen times before I committed to buy - knowing I can't easily change it once it is welded.  I got 3 quotes and Standley Steel of Wymondham were not only the most competitive, but were genuinely helpful people.

The main lintel over window and doors is 6m long and weighs around 250kg - a quarter of a ton.  it will need lifting 2.1m to put it in place.  The ridge beam, 4.5m long and only about 110kg needs to go another 1.2m above that.  I have a hand-operated crane on order for half term.  

Moving the lintel into the right position for the crane required some ingenuity, planks and rollers, and a car trolley jack.

I cut the hole in the back wall of the house for the ridge beam to sit in and checked it is the right size and depth.


So with the walls ready, the slab floor painted with two coats of bitumen damp proofing, the steel in place and the crane coming on Monday, all we can do now is go to Sheffield to see Ali for the weekend!

And So To The Walls

The next stage is to build the walls...


Not really rocket science I accept, but it is the part I have been looking forward to.  The dwarf walls, at damp course height first need a mortar bed - level all round - to lay the damp proof course on.  This is simply a thick plastic roll that stops moisture wicking up the wall by capillary action from the ground, so it is important that it is not breached at any point and that it is at least as wide as the bricks.  I chose 125mm wide dpc so it would overhang the bricks by 12mm each side. The overhang will be masked on the outside by the drip bead at the bottom of the render.


Before the mortar hardened I bolted the wall starters to the existing walls so I could tie the new blockwork in with the old.  The bricks drilled well, but after just three holes my Bosch cordless drill was running out of juice - I think it may need a new battery - so it was back to my old B&D which managed the job well.  I was pleased that the wall starters came with 10mm hex-headed screws so I put them in with a socket on the drill and tightened them up by hand.


Once the mortar bed had gone off and the dpc was set, I started to lay the blocks.  I use a Bricky tool to ensure a constant thickness of mortar and to cut down on wasted mortar.  It is a great piece of kit but it relies on the fact that you can get to both sides of the wall - something I patently cannot do with the wall up against Jean's conservatory.  The Bricky sets a 12mm bed of mortar so I cut a piece of 12mm OSB and fastened a batten to it that would give a 10mm overhang onto the blocks so I could match the bed the Bricky would set.

I discovered one thing straight away; if the bed runs right up against the adjoining all it gives no space for the excess mortar to be pushed out to - so the best bet is to leave a small gap alongside the existing wall for the excess to spread into when tapping down the block.

I am using a 5:1 sand-cement mortar mix and my mixer - the rusty legs of the stand having now been repaired with my rather dubious welding - holds 2.5 bags of sand and half a bag of cement at each mix.  I have been adding a small amount of mortar plasticiser to each mix to try to keep it useable for longer as I am a slow bricklayer.


I had two 3m lengths and 2 2.4 metre lengths of 4"x2" which I cut and nailed together to form a frame to build the door aperture around.  I cut a couple of spare pieces of timber to 45 degrees to brace the corners and keep it square.  the gap itself is 3m wide and will run for the full height of the wall up to the steel lintel which will extend pretty much for the full width of the building.

The insulation, 75mm thick Celotex board, is very easy to cut and slot into the wall cavity.  A basic hand saw does the job with no trouble at all.  It is the same product that I will use for the floor insulation under the screed.  It's not cheap but it seems the best product for the job.

The two different types of block I am using; 7Nm Medium Density Concrete block and 3.6Nm Aerated blocks cut rather differently.  The Aerated blocks cut with a saw to give a neat edge, the medium density blocks, on the other hand, need an angle grinder to give them a neat finish, but will cut with a hammer and chisel, if you don't mind a more jagged edge.   

The Slab

Once the sand was compacted and level I called the Building Inspectors to come and check it.  The inspector who came was very happy with it and was generally complimentary about the quality of the work so far.


I had bought 6 one metre lengths of 12mm rebar to join the new slab to the existing one.  These needed drilling into the side of the existing concrete - about 50cm - then locking in with injected resin.  This took a while but made a good join.  The difficulty then was setting the damp proof membrane on the sand and the perimeter insulation around the edge with the rebars coming through the membrane.  This has meant that the dpm is not watertight and I will need to paint a damp proof course on top of the slab before putting the insulation down.

I ordered 2.1 cubic metres of concrete - which I discovered was about 5.2 tons!  With enthusiastic help from Emily who waded in concrete and Zulum who chose the big barrow, we had the slab laid in good time in steady rain.  

The rain will not hinder the setting of the concrete, in fact slowing the drying process makes the curing better and results in stronger concrete; but it might spoil the finish. As it is not the top screed I'm not unduly worried about the finish - at least it's level.

By the evening it had pretty much set though it was difficult to see the finish.

Now that the floor slab is down I can start to build the walls, there i no need to lay the insulation and screed until I'm good and ready.  So the next phase is to attach the wall starter plates, lay a mortar bed all round on both sets of blocks and set the damp course on top.

Once that is on a second layer of mortar takes the next row of blocks all round, though the 3 metre gap for the bifold doors will leave a significant part of the wall looking rather bereft.  I will make a wooden frame, 3 metres wide and 2.1 metres tall, ensuring the corners are square, to use as a former for the opening.  A second one will be useful for the window over the sink.

More Digging

Now the walls are up to damp course level I can start to think about the floor.  I needed to dig all the existing soil from within the walls down to the bottom of the second bock down - a depth of about 450mm.  I think this would be about 3 tonnes of spoil, though after a few days of rain it felt like 10.

I could back-fill the trenches both inside and outside the walls with some of the soil, but there was still a huge amount to shift and I am running out of places to put it.  I am pleased that it is a relatively fast-draining, sandy soil that digs easily - I'd hate to do the same in the clay-soil we have at school!

I left a small gap in the wall to put planks through as a bridge so I could use the wheelbarrow to move the soil, but eventually I had to brick this up too.  Once down to the required depth I could start to bring back some of the bagged brick and concrete rubble I had stored from the demolition of the conservatory to use for the bottom layer of the floor.

There are several strata to lay:

• First a layer of 150 mm of compacted crushed concrete etc. to give a good, firm base. This is sometimes called Type 1 MOT because it is the standard of material specified by the Ministry of Transport for making the sub base for a new road.  I am going to use the bags of rubble I have made up from the demolition and clearing of the conservatory.  I have plenty of this and when it is compacted using a plate compactor it should be absolutely fine.
• On top of this comes a 'Blinding' layer of 25 mm of sand.  this covers any sharp edges and points that may puncture the damp proof membrane which sits on top of the sand.
• This is covered by either a 100 mm concrete slab or a 75 mm insulation board. It seems there are different thoughts about the order that these go in.  Some websites suggest the insulation board goes on top of the damp proof membrane on the sand, others that the concrete slab goes there with the insulation on top, and there are others that put the damp proof membrane on top.
• Whatever order these go in they are topped with a 50 - 75 mm screed to give a perfectly smooth and level floor surface.

The removal of all the soil from inside the walls took a while but was useful for back-filling around the outside of the walls on top of the foundations.  There was still plenty to get rid of, but I like digging.

I left the part nearest the drive until last because it made a very useful little access bridge but eventually even that needed to be demolished and the concrete drain-surround removed.

The hard-core went in well though the hire of a compactor was not without its problems.  The first one I hired worked for a couple of minutes but then stopped and would not be coaxed back to life even with fresh petrol and a new spark-plug.  So money returned I hired an identical one from HSS - identical in all ways except one - it worked!  Unfortunately this had left me considerably out of pocket and having lost a couple of hours of work time.

The sand I had dug out for the foundation trench would be fine for the blinding layer if it was sieved for stones - so I set about sieving a ton or so of it to lay a 25 mm layer.  The compactor worked well and the base was ready for the building inspectors to view before I lay the damp proof membrane and the concrete slab.