Adding second storey to existing ground floor extension

[CharlesBR]

I am looking at what options I have for adding a second storey to an existing ground floor extension (see picture below) that used to be a single detached garage built in 1989.

The first thought I had initially was that the roof would come off and anything else that would enable the brickwork to continue upwards. I plan to get a trial dig done so that a structural engineer can take a look at the foundations and get calculations done. I have read that it can be quite expensive when things need doing to foundations with needing to provide additional support depending on the soil condition etc if foundations are not adequate.

If it turns out that the foundations are not suitable then one other option I have read about is that a steel frame structure is constructed to take the weight of the second storey and a timeframe is used as the inner wall and brick is used for the outer wall so nothing looks different from the outside. Is this option viable and do I need to mention that to the structural engineer and architect as one of my options?

The approximate dimensions are roughly 5.4m x 4m (21.6m²) and I have a budget of around £45 to 50k (inc VAT) and live in the south east.

Thanks in advance!

 

[23vc]

Doubt that would be cheaper than underpinning

 

[^woody^]

I have read about is that a steel frame structure is constructed to take the weight of the second storey

Which goes on columns or posts which need pad foundations!

 

[CharlesBR]

Which goes on columns or posts which need pad foundations!

How much more complicated would that be and is the cost that much more than underpinning? I am a novice but I think I understand the way pad foundation work by placing the steel on top of concreate pads with various options (as explained here: https://theconstructor.org/geotechnical/pad-foundation-design-principles-types-selection/7514/) but I guess the type of soil depends on the size of the pad?

 

[^woody^]

Costs may not be very different between the two options.

Underpinning is done from the outside, pads will need part of the floor taking up and posts. But you may or may not need any extra work and its not good trying to plan anything unless you know exactly what needs to be done

 

[CharlesBR]

Costs may not be very different between the two options.

Underpinning is done from the outside, pads will need part of the floor taking up and posts. But you may or may not need any extra work and its not good trying to plan anything unless you know exactly what needs to be done

Gotcha, I will wait for a structural engineer to do his investigations.

 

[KatieDUK]

How did you get on Charles, I have a similar dilemma!

 

[jeds]

I'd start your own thread Katie. You'll probably end up needing specific advice to your situation which may differ from this thread.

On a general note; I'd be surprised if that garage foundation wasn't exactly the same as the house. I've set out and built hundreds of houses just like this and I can't remember one where the driver had to change a bucket for a garage.

 

[KatieDUK]

Thanks Jeds - Will do!

 

[CharlesBR]

How did you get on Charles, I have a similar dilemma!

Hi @KatieDUK, we got someone to do a dig down the side of the garage and the foundation goes a little over a metre and the footings are assumed to be 600mm wide (picture attached) so they will be likely fine to have the timber structure built on top. The structural engineer has recommended for steels to be installed front, middle and rear across the room to support the first floor and spread the loading using the garage and house foundations.
Building control have said they will need to inspect the foundations themselves before the build starts but this is standard practice.

 

[KatieDUK]

Thank you so much for taking the time to reply!