Extending height of blockwork shed - can I use different sized blocks?

[NathanFF]

Hi all,
this is my first post but hopefully not my last - I love DIY and am always looking to improve my skills. We've moved into a new house that has a block shed in the back garden - it had a flat roof that's absolutely knackered over the years so it's going to need a complete replacement.

The person who built this shed must not have been very tall because I'm almost having to duck at 5'9 when I look inside. So my plan is to add an extra layer of blocks to the existing walls and then secure the roof to these.

Here's the problem: the person who built it used what I can only assume are foundation blocks because I can't find anything else of the same size (they're 275 x 440 x 215mm!). Is there any danger in me using a more standard-sized Thermalite block (100mm thick) for this new layer and placing it toward the outside edge of the block underneath it (so it all looks flush from the outside).

With all the strain being downward force I can't see any problems but thought it was best to ask people more experienced in these matters before I crack on.

Kind regards,
Nathan

 

[Notch7]

Yes you can do that -although thermalites wont be any good if the block is the external finish, so use a concrete block

the other problem is that the roof joists will need tying to the sides with straps -fitting those only to the new course of blocks wont be good enough -I would recommend fitting a stud wall internally flush to the inside so there is a flat surface to run the straps down.

Personally as I am more into wood than blocks, I would forget the extra course of blocks and make up the additional height with say 150 x 50 timbers laid on edge (if 150mm is enough extra height), one flush to the external face, one flush to the internal face, made into a frame with noggins in between. Then finish the outside with a stepped fascia -1 to hide the 150mm and one to hide the roof joists.

The other option would be to fit 50 x 25mm battens vertically at 600mm ctrs all the way around and clad the block shed with timber feather edge -you would make the structure watertight as it would have a cavity and make the shed attractive (only worth considering if its in a position in the garden that needs making pretty).

 

[oldbutnotdead]

Be wary about overall height- you're limited to 2500 max external height within 2 metres of the boundary of your garden!

 

[domdee]

2 layers of concrete blocks laid on their flats will give you about 220mm extra height, and would be very stable. nice flat base for timbers to fastened to