Week 4 & We are hitting a few design issues

Week 4

We are hitting a few design issues... already.

firstly we had to confirm the roof truss size and specification - i thought that this had been agreed with the truss company by the surveyor. more on that later

secondly, now we have had a more detailed insight into the truss design it appears that the new section will have 200mm joists. which normally would be fine - but we have decided to leave the existing roof structure on the games room area of the house. The problem? the old section of house only has 120mm joists. So somehow we have to come up with a plan to combine the new and old - and make up the 80mm difference.

thirdly, the builder asked me today for the structural engineer calculations. 

These were completed last October and so i thought all issues had been resolved. The main one that has been on my mind since we started the design is the maximum deflection allowable for the bi-fold doors to operate smoothly. the issue being that the designed beam, which is 8 metres long, will deflect by around 8mm in a worst case. I looked on a set of the structural engineers drawings today and noticed that it says that the 'architect was informed' in October.  Somewhere something has gone astray in our communication!

So, the truss sizes and spec has been confirmed and the trusses have been ordered. Trouble is... their lead times have increased to 5 - 7 weeks. (up from 3 weeks when we last spoke to them). So now we are going to hit an issue where the builders run out of things to do before the trusses arrive. The builder has requested the order be marked as urgent... we will wait and see how that works out.

With regards the difference in size. we have two options. the first is to completely remove the existing roof and completely fit new trusses. the issue here is that we have not covered that section of roof with scaffold and based on the assumption that the roof would stay on this section of the house we are now intending on leaving the ceilings intact - hopefully saving some of the budget. So this option doesn't really work.

The second option is to increase the size of the existing trusses. The builder has suggested that each truss be increased in size by attaching extra wood to the top of it. This will work... provided the trusses can actually support the weight. Justin intends to fix two 2x2 battens perpendicular to each other across the whole roof. This will increase the thickness of the overall roof by around 100mm and so should line up with the new trusses... we hope.

Now onto the beam deflection. I am a bit peeved by this as i thought it was all agreed months ago. Basically the surveyor gave me the calcs for the steel beams today. The main steel across the windows is around 8 metres long and spans the 6.5 metre opening. The calculations suggest the beam will sag by unto 8mm in the centre. 

The issue is how much deflection the bi-fold doors will take... my feeling is it will be less than 8mm.

The solution will probably be to add in a central support pillar - not ideal as this is what we wanted to avoid. We will find out more on Friday.

I thought that was all the issues for one week the we spotted another. 

The screed over the UFH in the kitchen looks like it has completely broken down where it has been covered with tile adhesive. So as the builders have been removing the tiles the screed has just crumbled away - revealing the UFH pipes!! Potential disaster waiting to happen. At this stage we think we will have to dig up all the screed, carefully revealing all the pipes and then re-screed the whole area! We will know more in a few days time.

So, after two good weeks of progress we have hit a few little humps in the road. Watch this space for more to follow...