Two storey extension method

[garyo]

When building a two storey rear extension, what's the normal order of doing things in situations where the existing back wall won't be present in the finished house?

Would you tend to build the new shell, knitting the new brickwork in to the outer skin of the existing house, and then when the roof is on knock through and knit in the internal leaf brick work, make good etc?

Or would you go for maximum disruption and take the back wall down on both storeys, (propping the floors and roof if required) and then get the new extension built and watertight damn fast?

I can see the attraction of the former option, but there's always going to be a degree of re-work when the cavity is exposed knocking through, so it's probably not the most efficient, but probably the one that the homeowner would prefer...

Gary

 

[^woody^]

You would build the shell first before knocking through. But whilst the build in is progress, run a disk saw along where the external openings are to be formed, so that when the time comes the walls can be removed easily without too much knocking about.

 

[noseall]

There are often occasions where we will insert the steel beams into their position long before actually getting to the stage of doing the knock out.

This is especially relevant when the new steel beam location is at joist level and the new joists interfere with the installation process.

We would also in this instance remove a single course of masonry directly below the steels in preparation for the knock out so that there is no 'trapping' of the masonry. This gap would be filled with fibreglasss insulation to prevent drafts and would not be wide enough to admit a burglar or any other scrote.

 

[garyo]

Thanks guys.

Interesting what you say about the steels, nose. Makes sense and I guess it would come down to floor joist directions if you want to sit them inside an 'I' beam. So in the short term the steel might have to be strong enough to support a first floor masonry wall that will disappear after the knock through.

After the knock through would you fully knit in the brick work in the inner leaf, or simply close up the cavity with vertical bricks? I suppose you must see some situations where the inner leaf on the extension is made from low density block work and the inner leaf on the original house is brick?

 

[noseall]

After the knock through would you fully knit in the brick work in the inner leaf, or simply close up the cavity with vertical bricks? I suppose you must see some situations where the inner leaf on the extension is made from low density block work and the inner leaf on the original house is brick?

In some instances an overzealous structural engineer may insist that the wall jambs are toothed out and relaid with a 'bonded' repair.

However, in most scenarios a simple block slither is mortated up the cavity.