5m x 4m detached garage

[Chris2016]

Hi,

Looking for some advice. I am building a garage for my friend onto a concrete base. It will be a single skin concrete block wall. Will this require a DPC or not?

Also in the 5 meter straight wall I was going to tie in two pillars. For the 4 meter i was going to put one pillar in the centre Will this give it enough?

Thanks for your help.

 

[John D v2.0]

dpc is to stop water damaging the structure or coming to the inside of a habitable space. So the simple answer is no, as you are use frost proof blocks and no timber in the walls presumably.

However my other answer would be why not - noone likes to store their good possessions in a damp garage. Although I assume the base is already laid at ground level without a dpc.

 

[Chris2016]

Hi,

Thanks for getting back to me. The concrete slab has a DPM in it. As its just a single skin (4" concrete block) with pillars Im not clear weather the blocks should have a dpc after the 1st course or not??

Thanks

 

[cjard]

A roll of DPC costs pence; what are you thinking to gain by not putting it in?

 

[Chris2016]

It's not that. I'm just was not sure if its needed one or not. I just thought because it was a standalone garage and a single skin, it would not be needed. I could not make up my mind what to do.

However I remember when I have put dpc onto a 4" block wall the blocks tend to slide about on it because the dpc is just a bit wider than the blocks. I guess weight of the blocks above holds everything in place. I kind of think this makes a weak point in the wall though. If I put the dpc in does it mean that the first course is not really bonded to the second because of the dpc separating them. On a double skin wall it would be fine because you would have wall ties going up every second course.

 

[cjard]

Put a DPC in for all the reasons, relating to moisture, that you should. It doesn't really make a weak point with regards to what a wall does as normal service, because walls don't just stand up because they are stuck together with mortar.

I could show you a picture of one of my brick garages where the bin wagon hit it. The corner of the wall folded round, crushing the garage door. The courses below DPC were unmoved, but there's no way on earth that not putting a DPC in would have meant the wall held firm and showed no signs of damage.. it would have still folded round albeit in a different pattern, so don't be concerned about a DPC having any deleterious effect on the wall structure for its normal operation

Additionally, both skins of a cavity wall have a DPC, so it's not correct to say that two skins tied together resolve a failing that a single skin wall suffers from having a DPC

 

[freddiemercurystwin]

Jeez just fit one for FFS, where exactly do you think the wall will go when there's a couple of metres of blockwork and a roof sat on it?

 

[John D v2.0]

You shouldn't be building a wall that long without some buttresses anyway, off the top of my head you'd need a couple along each wall and then tied together at the top by the roof. Masonry isn't very strong in tension anyway but if you make it into a box it's a lot stronger. That's why the building regs make you get a structural engineer in when you want to knock out your rear wall for massive bifolds. Then there's a good chance he'll specify steel goal posts rather then a beam on the walls.

 

[cjard]

I think you might be getting a bit carried away with the buttresses there john. A couple in each 5m wall would mean you have a buttress every 1.5m, which for a single storey building less than 3m high and tied in at the roof and floor, is a bit over the top.

 

[Chris2016]

Thanks for your reply's. I will put a dpc in. I think I was over thinking this.

I am planning on tying in two pillars in the 5m meter wall and one in the 4m wall. Will put some of that bricktor in every second course in the pillars and at the door openings.

 

[John D v2.0]

Cjard I may well be, but your thought is probably as good as my top of head for the op! i was hoping someone would really find a reference for him