Cavity details under patio door

[trevorbayliss]

I am getting on with the extension and i have a question about fitting the patio door next spring.

The door will sit on the external brick work, but i assume it will be sitting slightly back off the brick as the door will be about 100mm deep. so my brick is 110mm deep and the patio will be set 20mm inside of the brick. so i will get an overhang of 10mm approx.

Is this ok, or could the two cavities be tied together at about 4 places so making a stronger base for the door. If you tied them together what would you use ? I was thinking about filling in this cavity, but BC said i still needed it for drainage. Is this correct because there will be no brickwork above it, just the patio door.

 

[Blagard]

Cavity drainage could flow along the cavity before leaving via a weep hole. Personally I have closed such cavities as you would close the cavity under a window cill the difference is I want to extend the floor finish across the same as the rest of the floor and sometimes the outer leaf can be a bit higher than the floor level. Depending in what type of DPC or DPM you have internally you need need to adjust the detail to suit. But I have whipped out the inner brick course, bedded a row of creasing tiles to close off the cavity low down and act as permanent formwork then put in a DPM/or DPC to cover the tiles and lap onto existing DPC/DPM details. Then concrete on top to suit the levels I want. If the outside brick under the frame is a tad too high for the floor and the frame is already in so you cannot easily cut a rebate into the brick I would cover the exposed brick aris with an angle trim, easy if the frame is PVC use a PVC angle. Otherwise if the frame is wood, a rebated wood section the same material as the frame.

 

[trevorbayliss]

On top of the inner course will be a timber batten and this will carry my oak floor up to the patio door.

The external brick line will be my finished height i think pictured. I have laid a DPC under this line of brick the width of the patio so it won't be punctured when the patio is screwed into the brick (you can just see it in the photo). This actual brick line is the height of my DPC all the way around, so today i will be laying another DMP over this section as well.

The way i am planning on closing the cavity is with a cavity close kit which has polystyreen on the back.

My main concern is that the heavy patio door is ok hanging over the back of the brick line a little. I think the door will weight about 250kg. Will it be ok sat like this ?

 

[Blagard]

On top of the inner course will be a timber batten and this will carry my oak floor up to the patio door.

The external brick line will be my finished height i think pictured. I have laid a DPC under this line of brick the width of the patio so it won't be punctured when the patio is screwed into the brick (you can just see it in the photo). This actual brick line is the height of my DPC all the way around, so today i will be laying another DMP over this section as well.

The way i am planning on closing the cavity is with a cavity close kit which has polystyreen on the back.

My main concern is that the heavy patio door is ok hanging over the back of the brick line a little. I think the door will weight about 250kg. Will it be ok sat like this ?

The 10mm overhang is no problem. The cavity closer is absolutely fine if the external leaf is low enough for the internal floor finsh. (The cavity closers I have used rest on both inner and outer leaf for support) The only issue I would have is if the oak floor is laid with joints parrallel to the cavity closer. Those closers can't take any real weight

 

[trevorbayliss]

The weight will be taken by the 4x2 length of wood sat on the inner course. The oak will then extend out to the patio door and will be sitting over the cavity gap which will probably be 90-100mm. I suppose i could reduce this gap down if i screw another length of timber on its side and sat in the cavity. It would reduced down the fresh air gap by 40-50mm.