It’s been a week of frustrations and setbacks, albeit fortunately just small ones. Putting in the windows has thrown up some surprises and the rain has caused a few problems too. But the team have been working really hard and overall the site is showing its potential for a great office space already.
Corroded lintels
When the windows started going in it became horribly apparent that all was not well with several of the existing lintels. In fact they had completely degraded. The high tensile steel cables inside the concrete had rusted over time, and had then expanded, causing the concrete to crack and crumble all the way along. Alex thinks it’s likely they were built using sea sand rather than quarried sand, a practice common here in the 1960s, which has led to all sorts of problems with buildings in this area.
When the lintels were taken out they immediately crumbled into pieces. Fortunately only 4 of the windows were affected, and largely it was just the lintels on the outer wall – the weight of the wall resting largely on the inner lintels – so we were extremely lucky (not to mention happy) not to lose any brickwork! It looks like it’s only put back work a day or so.
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- The old lintels, completely split along the length
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- New lintels have had to go in above several windows
Missing out on an air tightness test
The bigger problem is that as the windows are still going in we’ve had to miss out on doing another air tight test. Carrying out regular tests is a really important part of a Passivhaus or EnerPHit build, as you need to know how you’re progressing and where the problems are.
So we still haven’t done a full test since the roof was sealed.
A leaky gable
Tiling starts
Yet more heavy showers! Up on the end of the roof, where the air tight membrane was sealed to the gable wall, the water ran down along the wall and came through to the inside, showing us that the materials we used were still not entirely waterproof (despite the change of tape I wrote about in Week 6’s diary!). The team have had to use another product now to seal the area – a PU (polyurethane) based primer which will penetrate into the render and seal it up again. They will then have to replace the insulation and membrane layers, this time using a waterproof sealer on the top edge of the tape to stop water getting in between the tape and membrane again. This should keep it all nice and dry until the lead flashings – the permanent waterproof layer – go on.
Aside from this the tiling is well underway now, and work is almost ready to move back inside.
Finishing the windows
Once the lintels are all replaced the next job is to finish off the window reveals and boxing, ensuring the windows are all completely sealed before the cavity fill insulation goes in.
The frame sits out from the wall
For the reveals the plasterboard will sit in the groove of the actual window frame and is then glued back into the wall with plasterboard adhesive. As the PU foam cavity insulation is pumped into the wall space, it will also spill into the space behind the reveal and under the window sills, to completely fill this space and sealing it all up to create a fully airtight layer.
Plasterboard will be used to construct the reveals
I’m really interested to see the final structure of the windows – already as you walk up to the building you can see how great they look from the outside, and inside they’re letting in lots of light and really opening up the space.
