Party Like It's 1999 (2015 edition)

A Party wall is a main separating wall between buildings.  Responsibility for the wall is normally shared between the owners of the buildings (the parties).  In this case the Party wall is the wall which separates the two homes within this semi-detached building.

The last time i worked full-time as a joiner was 1999 and whilst the skills and techniques remain the same, the building regulations of 2015 have changed a wee bit.

The party wall was parged (coated in cement render) at the start of the year.

The building regulations require the construction of a 150mm x 50mm partition at the party wall.  This partition, like the oxter walls, will need to be insulated by the fitting of 145mm insulation batts and 40mm Kingspan/Celotex insulation board.  In the case of the party wall partition the 40mm insulation board is to be fitted on the back side of the partition and i've left space in the partition (the missing dwangs) for this to be slid into place later in the project.  It saves a £50 delivery charge if i make one large order of insulation with free delivery rather than 1 small and 1 large order.

One of the other changes in building regulations is that a minimum gap of 25mm must be kept between the back edge of the finished partition and the party wall to ensure adequate ventilation within the loft space around the whole 'box' of the conversion.  In this case the back edge of the partition will be the insulation board and the bare timber partition had to be built 65mm away from the wall to account for the 40mm insulation board.

The Party wall partition requires to be finished with two sheets of 12.5mm plasterboard which are then to be fully plastered, so overall the finished partition will be approx.. 220mm broad.  Hopefully that should provide adequate thermal and acoustic insulation between my neighbours and I. 

Heatseeker

Now that all the joists are in place it's time for the 1st round of insulation fitting

In the eaves, behind the steel beams, some of the original loft insulation was re-laid in between the joists.  Prior to re-laying I had to fit an eaves ventilation roll.  This is a corrugated plastic roll which ensures that there is a decent gap for airflow into and around the remaining loft space from the external eaves vents.

Sometimes people fit loft insulation and stuff it right into the eaves restricting air circulation and creating good conditions for condensation build up, fungal growth and potentially dry rot.  

I laid a second layer of insulation across the joists on top of the insulation laid between the joists to give at least a 300mm layer of insulation within the area of the loft which will not form part of the new room.  

One of the first jobs to be done way back at the start was to lift the existing insulation and i was surprised to find a layer of loose cork insulation under the original loft flooring.  A quick check on t'internet showed that loose cork had the same insulation qualities as approx 150mm of modern insulation quilt, so i set it aside and then when the time came I just poured it in between the joists of the floor of the new room before laying 100mm of insulation quilt on top. Not only will this provide good thermal insulation it should also improve acoustic insulation between the new room and the rooms below.

Dwanging, hope you like dwanging too.

With the steel beams fitted and secured in place, it was now time to fit the structural joists which would form the new floor level and would be hung from steel beams using the twisted hanging straps.  The picture above shows the flitch beam in place and hung from the steel.  The flitch beam will help provide structural support for the stairwell opening.

This is the future stairwell opening.  All joist ends are hung from joist hangars and the two joist hangers at the far side are bolted through the joist into the chimney breast wall.  The flitch beam is the large double joist nearest to us in this picture.  The existing 6"x 2" joists have simply been cut and are sitting in place until the time comes for the stairwell opening to be cut.  The opening will be circular to fit the shape of the planned spiral staircase.

As you can see, the building up of the existing 6" x 2" joists to create 9"x 2" sized timbers which were then sandwiched between the 9"x 2" joists has created very substantial timbers which span the length of the loft and are hung under the steel.  Fitting all of this took twice as long as i had initially thought (and was twice as dear) and as a result I'm now about 1 month behind schedule (and budget).

Once the joists were fitted and hung from the steel the entire floor had to be dwanged out.  Lots of little 9"x 2" dwangs all needing to be cut to size, knocked into place and nailed.  My knees don't like dwanging!

As well as dwanging the joists the oxter supports required to be fitted in their final place.  The supports were moved back approximately 8" from their original place on each of the 3 sides of the loft and this should create a room which is 5m x 5.5, (incl. the en-suite).  The supports were bolted through the roof trusses with toothed connector plates in between.

All of the structural joists were hung from the steel, with the twisted hanging straps used on both sides of the steel beams and nailed in place with twisted square nails.  As per the structural engineers specification, the steel beams each had to have two restraint brackets fitted which prevents rotational movement of the beams.

After all this was done the work was inspected by the Building Standards Officer of the Council and i'm pleased to say that it was given the seal of approval.  Onwards and upwards.