Concrete outbuilding foundations

Joined
30 Aug 2022
Messages
3
Reaction score
0
Country
United Kingdom
I'm building a 5x3m 2.5m high single skin concrete outbuilding. It will act as a gym.

I'm looking for advise with the foundations.

Based on Structure: Approved Document A the width of the footing is advised to a be a minimum width of 250mm and depth of the excavation 450mm based on my wall and ground type.

I initially planned to pour a concrete footing but discovered thermalite trench blocks have a width of 300mm. Access to pouring concrete is problematic and would prefer not to do if possible. I would

1. Given the trench blocks have a width greater than the advised minimum footing would it be okay to solely use the trench blocks 2 courses high with no concrete poured footing?
2. The walls will be 3.6n aerated concrete. Is this also permissible for the below ground structure? I think there are higher density blocks available in that size but unsure if they would be overkill?

Thanks
 
Sponsored Links
Joined
3 Aug 2022
Messages
103
Reaction score
29
Location
Worcestershire
Country
United Kingdom
Interesting question. I don't see why not. It'd probably be sensible to pour a 50mm levelling/blinding layer, but you could achieve something similar with dry mix mortar.

Guessing you're on gravel/sand?

Other option if you're doing a concrete floor and need to pour that, is to change it to a raft slab. Walls would be built off the slab.
 
Joined
30 Aug 2022
Messages
3
Reaction score
0
Country
United Kingdom
Thank you for the reply.


I've made the assumption I'm on chalk. I'm pretty sure I will need a pick to excavate given the local area. I will dig a few test holes.
 
Joined
18 Oct 2021
Messages
127
Reaction score
29
Country
United Kingdom
I’d just pour a 150mm thick x 300mm wide concrete strip foundation. It’s less than a cubic meter of concrete which in comparison to most foundations is practically nothing.

What are you doing for the floor?..
 
Sponsored Links
Joined
15 Sep 2017
Messages
30,506
Reaction score
2,377
Location
S. Uplands
Country
United Kingdom
I'm building a 5x3m 2.5m high single skin concrete outbuilding. It will act as a gym.

I'm looking for advise with the foundations.

Based on Structure: Approved Document A the width of the footing is advised to a be a minimum width of 250mm and depth of the excavation 450mm based on my wall and ground type.

I initially planned to pour a concrete footing but discovered thermalite trench blocks have a width of 300mm. Access to pouring concrete is problematic and would prefer not to do if possible. I would

1. Given the trench blocks have a width greater than the advised minimum footing would it be okay to solely use the trench blocks 2 courses high with no concrete poured footing?
2. The walls will be 3.6n aerated concrete. Is this also permissible for the below ground structure? I think there are higher density blocks available in that size but unsure if they would be overkill?

Thanks
Foundation depth is decided by the load bearing capacity of the ground and its stability. That’s influenced by ground type and whether there are any trees within the zone of influence.

You could hi density concrete blocks up to DPC and thermalites above.

Im not sure what wall construction you are intending but a single skin wall has both damp and thermal issues. If you want a modern external finish like smooth render, I would use tyvek housewrap, vertical battens then rendaboard. That creates a cavity and keeps the wall dry.
 
Joined
3 Sep 2006
Messages
37,355
Reaction score
5,468
Location
West Mids
Country
United Kingdom
That foundation recommendation seems too narrow and too shallow.

Two course of blocks direct onto the ground won't have sufficient load transfer capacity and risk cracking.
 

DIYnot Local

Staff member

If you need to find a tradesperson to get your job done, please try our local search below, or if you are doing it yourself you can find suppliers local to you.

Select the supplier or trade you require, enter your location to begin your search.


Are you a trade or supplier? You can create your listing free at DIYnot Local

 
Top