Foundation for timber frame

[deuce22]

Hi.

Can someone please give me some advice on the correct way to construct a raft foundation for a new timber frame build.

I would like to know the dimensions and the way it is constructed.

Thanks.

 

[freddiemercurystwin]

House, extension, single/double storey, shed, garage, outer skin masonry, no outer skin, cavity width? Why raft? Questions questions ............

 

[^woody^]

Don't you just dig a rectangular shape out of the ground?

 

[deuce22]

I'm in the process of buying a building plot and I'm more than likely going to be having a timber frame construction.

I have been told that it only needs a raft/slab foundation, but I am not familiar with this process.

I have seen pictures, (there is a side profile attached) and realise that the outer perimeter has to be lower to act as a cavity tray, but I'm not sure what the setup is to be able to form this.

http://www.homebuilding.co.uk/files/ascent-homebuilding/images/2007_08/building_trench.jpg

Thanks.

 

[Static]

You need to give alot more information,ie. type for ground your founding into? As well as dimensions, storeys, as said above etc etc..

But given basically you strip out the topsoil and a good 150-300mm below, put in type 1 well compacted subbase, blinding, dpm, then some steel rebar to span soft spots and concrete.. job done..

But if you have heave suseptable clayie soil then you are better off with pad/tbeam rather than rafts..

Also consider services when planning rooms.. or put in a floating floor..

 

[deuce22]

Hi static.

I assumed that you always used a raft type foundation when building a timber frame construction.

All the companies I have spoken to have told me that, that is what is required.

Am I correct in saying that each build is different and it is the ground that dictates what can be used.

The other reason I was planning a raft is due to the speed of which it is done.

I understand the preparing of the site before the poor, but I cannot grasp how the slab is formed.

Around the outer perimeter the concrete steps down.

Obviously doing this in two stages is pretty straight forward, but I have been told that it is pored all in one go.

How to you create this stepped edge, do you have to form it yourself by shuttering it off.

Thanks.

 

[Static]

Precast concrete beam and pad foundations can be an option.. but yes raft is the most common.. cant remember the companies that do the precasts sorry..

Can be done in one go but you may not get a good surface on the lip.. might be simpler to do two pours..

 

[^woody^]

Foundation type is determined by the ground conditions not by the fact that it is a timber frame.

Have you just had sales patter from these frame companies?

The edge detail will depend on the frame and external cladding type, and needs to be properly designed, along with any required thickening or edgebeam