March 30, 20215 yr We're using 253mm high posi-joists (Mitek system already purchased) for our two storey detached house. The reason for using posi-joists is MVHR. The posi-joists will sit on top of the 100mm blockwork inner skin at the required height (we are not using joist hangers). We are planning to use the tony tray technique for airtightness around the joists. The problem is the joists are 253mm high (compared to blocks which are 225mm high with the mortar joint), so am I correct in thinking we will need to notch out a bit of the block above around the top of each joist (to enable the blocks to continue up in sync with the external skin) and carefully lap the membrane around the notch as we go? Thanks Edited March 30, 20215 yr by Johnny Jekyll
March 30, 20215 yr Who did the drawings or design and worked out the joists are 253mm high? Can you ask them (presuming they design and sign off on the calculations) if you use joist hangers as it would make things far easier? While possible it will be very messy and time consuming trying to have the membrane stretch around the notched ends of the blockwork.
March 30, 20215 yr Author 29 minutes ago, Dudda said: Who did the drawings or design and worked out the joists are 253mm high? Can you ask them (presuming they design and sign off on the calculations) if you use joist hangers as it would make things far easier? While possible it will be very messy and time consuming trying to have the membrane stretch around the notched ends of the blockwork. Thanks, unfortunately the posi joists are already on site so gotta find a way around it. Notching the blocks looks like it will have to be.
March 30, 20215 yr Author 1 hour ago, Dudda said: Who did the drawings or design and worked out the joists are 253mm high? Can you ask them (presuming they design and sign off on the calculations) if you use joist hangers as it would make things far easier? While possible it will be very messy and time consuming trying to have the membrane stretch around the notched ends of the blockwork. The joists were at 253mm so that the mid floor area would have enough room for both steels and MVHR ducts to run past each other. Very annoying I know.
March 30, 20215 yr You can use joist end caps - only cost £4/5 each depending on size. I have used them on mine and can grab some photos when back to site tomorrow if you want? These allow for the timber shrinkage and have a foam airtight seal facing the block.
March 30, 20215 yr Aren’t blocks 215mm ? can’t you have a run of bricks somewhere to reduce the height?
March 30, 20215 yr The joist lift is a pain in the arse for brickies either way and they will have priced for a fair amount of faffing about you would have thought. To give you an idea the joist lift on mine was £3500 (labour) vs £5k for the 1/2/3rd lifts.
March 30, 20215 yr I would ask about notching the top of the position joist or redesigning them to be 225 high where they go in the wall. Unlikely but theoretically possible love the idea of the tony tray ?
March 30, 20215 yr Author 4 hours ago, Faz said: You can use joist end caps - only cost £4/5 each depending on size. I have used them on mine and can grab some photos when back to site tomorrow if you want? These allow for the timber shrinkage and have a foam airtight seal facing the block. Yes please photos and a website link if possible to where I can see them would be great. Thanks.
March 30, 20215 yr Author 1 hour ago, TonyT said: Aren’t blocks 215mm ? can’t you have a run of bricks somewhere to reduce the height? Yes 215mm / 225mm with the mortar joint. No can't really have a run of bricks.
March 30, 20215 yr Author 1 hour ago, Faz said: The joist lift is a pain in the arse for brickies either way and they will have priced for a fair amount of faffing about you would have thought. To give you an idea the joist lift on mine was £3500 (labour) vs £5k for the 1/2/3rd lifts. Again great info thanks.
March 30, 20215 yr Author 28 minutes ago, tonyshouse said: I would ask about notching the top of the position joist or redesigning them to be 225 high where they go in the wall. Unlikely but theoretically possible love the idea of the tony tray ? The joists are already here so another order would cost £1500+ I'll ask the bricky and see what they say. Thanks.
March 31, 20215 yr 20 hours ago, Johnny Jekyll said: Yes please photos and a website link if possible to where I can see them would be great. Thanks. Here you go mate. As you can see from the box they came from Manthorpe - the merch will be able to source them for you. The sudden summer makes life hard on site when it comes out of nowhere btw!
March 31, 20215 yr Author 4 hours ago, Faz said: Here you go mate. As you can see from the box they came from Manthorpe - the merch will be able to source them for you. The sudden summer makes life hard on site when it comes out of nowhere btw! Thanks very much Faz.
Create an account or sign in to comment