Foundation advice

[deuce22]

Hi.

I am looking for some information on the different types of foundations I can use for my project.

It is a Dormer Bungalow, but I am not sure yet whether I am constructing it as a timber frame or traditional.

I would like to know the price comparison between each type and what the ground requirements are.

Cheers.

 

[Blagard]

You are starting the wrong way round.

First you establish what your ground conditions are, then you can consider the foundation options. You also need to mention if this is DIY or using a contractor as the labour/plant element will vary significantly!

 

[deuce22]

Hi Blagard.

I will be using a digger plus driver for the excavation, but myself and father will be managing everything else.

How do you establish ground conditions yourselves or should I get the BCO to tell me what I can do?

We've done many extensions in the past and have just gone straight ahead with a strip foundation. We have never had a BCO query what we have done, they have been happy with that.

We normally do strip foundations and trench fill as it is only slightly more costly, but it is done and the bricky can crack straight on.

I can remember someone telling me that they poured the concrete in one whilst doing a strip foundation, but I don't know how to do this or even if it is allowed.

I'm looking for the most cost effective, efficient way.

Cheers.

 

[jeds]

Not sure I fully understand your question. The foundation for a timber frame or trad cavity wall would be the same. Simplest and cheapest solution for both would be a strip foundation. Without knowing actual ground conditions you should plan for a 600mm wide and a metre deep. This will cover 90% of situations.

Alternatively you could do a trial dig but bear in mind it only tells you what the ground conditions are near the site of the trial. You might still find variations around the site when you pull the foundation.

 

[Blagard]

I think you have practically answered your own question.

Strip foundations are simple and easy to use on the vast majority of projects. Trench fill gets you practically out of the ground without having to mess around with any more than the minimum substructures brickwork. So it saves time and cost of the brickies, but you spend a more on concrete, and possibly have more material to remove off site if space is a problem.

Doing trench fill all in one go is how I would expect it to be done. Dig trench let the BCO see it then pour the concrete to top of the trench fill level. Very hard work if mixed on site.

If you were thinking of raft foundations, they require proper design, reinforcement and the additional lead in time. So factor in Engineer fees, reinforcement costs and time. You may find the building control officer's don't like them when a simple strip foundation is all that is required. The benefit may be reduced cost of removing excavated material off-site. Usually used as an alternative when strip foundations would have to go much deeper than usual to satisfy Building Control.

Piles are generally for difficult ground conditions, they usually involve specialist and expensive companies, so leave that one out

I'm not familiar with any other for a domestic job.

Bottom line is use a strip foundation unless there is a reason not to. Trench fill for speed and convenience if that is worth something to you.

 

[deuce22]

Hi.

The reason I asked was that over the last 6 months I have been driving around to many sites doing some of my own research.

Everywhere that I have been, they have used a raft foundation.

I then went to a local timber frame company and he assumed that I was using a raft.

I just thought that due to the lighter weight of the building this was the preferred method when using timber frame.

I agree that a strip foundation is pretty straight forward, so I will try and go this way.

Is there a way to pour the foundation and oversite in one go, as I have been told.

Cheers.