Block & render garage - Quick questions please :)

[helvellyn950m]

Hi all,

This forum has been really helpful over the years, I've really appreciated the help from others.

I'm sharing my new Garage project over on a build thread, but I'm after a bit of advice before I start. Just 3 questions if someone more knowledgable could give up a little time

1. There'll be a DPM beneath the slab. Walls built with grey block. Is there a need for a DPC in the walls? After the first course of blocks?
   
   
2. Is it easier for the brickie if I design the wall dimensions in "whole bricks"? What's the usual allowance for mortar with standard solid blocks?
   
   
3. Once the slab is laid and the formwork removed, there'll be a gap between the new slab and the existing drive. Could I fill this with gravel to act as a soakaway, or is it bad to encourage water under the slab?
   
   There are no drains anywhere near the garage, so I'm wondering where the rain should run. Run-off is ever so slightly away from the house, towards the garage and the road. I don't want water to run against the new building, but I'm not sure about channeling it out across the footpath either (I'm thinking about ice for pedestrians in winter). Any ideas?

Thanks for your help

Chris

 

[noseall]

Is there a need for a DPC in the walls?

Yes. Two engineering brick courses above the slab depending upon ground levels etc.

Is it easier for the brickie if I design the wall dimensions in "whole bricks"? What's the usual allowance for mortar with standard solid blocks?

A block and a joint equates to 450mm horizontally and 225mm vertically.

Once the slab is laid and the formwork removed, there'll be a gap between the new slab and the existing drive. Could I fill this with gravel to act as a soakaway, or is it bad to encourage water under the slab?

Are you building foundations?

There are no drains anywhere near the garage, so I'm wondering where the rain should run. Run-off is ever so slightly away from the house, towards the garage and the road. I don't want water to run against the new building, but I'm not sure about channeling it out across the footpath either (I'm thinking about ice for pedestrians in winter). Any ideas?

Dig a soakaway and run the storm into that.​

 

[helvellyn950m]

Thanks for your help noseall

Are you building foundations?

No foundations, just a keeled slab base:

Concrete garage base

• helvellyn950m
• 4 May 2020

Credit: https://www.pavingexpert.com/concrete#construction-drawings

 

[oldbutnotdead]

What ground are you building on? 300mm seems awful shallow for the footings. If you're on clay a soakaway won't work, you'll need to connect guttering to the house drainage. Wouldn't worry too much about the groundwater dropping into the joint between garage and house, if your gravel trench doesn't work then put an ACCO drain in & connect it to wherever the guttering drains to (soakaway or mains)

 

[noseall]

Thanks for your help noseall



No foundations, just a keeled slab base:

The image you show is a raft foundation. Costly and more of a faff over a trench foundation - with possible nuisance damp issues with that dreaded projected toe.

 

[helvellyn950m]

Thanks Chaps, you've both given me something to think about there!