Adding on to block outbuilding

[sirocosm]

I would like to build a workshop in my back yard 4x7m. Currently there is a 3x4m outbuilding made of block and rendered. Originally I was thinking to rip it down and start from scratch, however removing all the waste and digging out the foundation seems like a lot of work for nothing, so I am thinking to just extend it to 4mx7m. The roof is rotten, but the block part looks very well built, no cracks and very stable. I was thinking to knock down one wall to the corners, cut notches for the new blocks to key into, and render the exterior when finished.

Any pitfalls with such a project?

 

[oldbutnotdead]

Main one is foundations. If the existing shed has none then it'll move differently to the new bits (which presumably you will dig footings for)- same problem if the existing has proper foundations unless you tie the founds together. But for a shed/workshop, go for it- you might be better using wall starter plates rather than toothing in, if you do get any differential movement just fill the join with caulk or silicon and cover it with painted timber. Render- up to you, again for a shed why worry?

 

[sirocosm]

Thanks. I will have a dig this weekend, and if there is a decent foundation underneath I will plan to drill holes and pin rebar into that. I was planning for a 60cm deep x 45cm wide trench fill to just below grade, and then block on top of that. However, maybe it would be better to just match how the existing was done? It has been there a while, and there are no cracks or evidence of sinking.

I thought render (stucco?) because it is cheap and easy to make it all look the same, and it will match our house, which has brick down, render up. I am planning to buy a small electric mixer and do the lot myself.

 

[Notch7]

Id be tempted to fit 50 x 25mm battens around, then screw rendaboard on.

rendaboard is designed of course for rendering, but I wouldve thought you could get away with just painting it

The advantage is that the cavity will mean the block walls wont suffer with damp.