Extension question - chance to add a second floor?

[Syla5]

Aimed mainly at our resident builders / those in the know regarding building regs etc.

We have an extension on the back of our house, its a large lounge that is single story built in the 1980's. It has a pitched roof, and the roof beams are considerable from memory they are easily over 1ft deep and at least 4" wide, and they are spaced around 2ft apart at most I believe.

They appear to be of load bearing capacity for a second floor.

My questions then are:
1)were regulations such at the time that the foundations would have to be deep enough to support load for a 2nd story?
2)What is the likelihood that we will be able to go above the current extension?
3)Assuming we can go above the current extension, should this be more straightforward then building the whole extension from the ground up?

 

[Maccapacca]

Anything is possible, you'll need a trial hole to determine the depth of foundation and whilst it's exposed a visit from Building Control who will confirm if it's suitable for your proposals.

If you're on clay or have any trees or bushes in the vicinity the answer will probably be no, simply because regs have changed and they'll probably want deeper than you have.

 

[Syla5]

Anything is possible, you'll need a trial hole to determine the depth of foundation and whilst it's exposed a visit from Building Control who will confirm if it's suitable for your proposals.

If you're on clay or have any trees or bushes in the vicinity the answer will probably be no, simply because regs have changed and they'll probably want deeper than you have.

I would assume that its easier to knock down and start again if the foundations are not suitable?

Nearest trees are a good 15-20ft away, no bushes.

 

[Maccapacca]

Yes, underpinning and or mini piling is very costly, if you think you'll have to remove the roof anyway you may as well grub the lot out and start again.

 

[Syla5]

the roof would definitely be removed, however if the foundations were suitable the plan was to just go straight up from there, or am I being naïve in thinking that's possible?

 

[Maccapacca]

No no that would defiantly be the cheapest option. If you had to start underpinning the existing the cost would outweigh just pulling what's left down, starting again with a modern build.

Be worth looking at a timber frame you could plonk on top but again you can plan all you like if the building inspector says the foundations aren't suitable you're a bit stuck. Firstly I'd get someone to dig down and survey what's there before you make any decisions.

 

[Syla5]

That's the plan, get someone in first before doing anything. If it ends up doubling the cost of the build then its not worth it.

 

[Sunbed]

Have you considered planning? I think you need to go through the full process if you're building a second story.

 

[Syla5]

Have you considered planning? I think you need to go through the full process if you're building a second story.

...this is a long term plan, I was just fishing around for opinions based on the little information I have.

Of course when full extension plans go ahead the first thing to do will be dig a test hole and get building control in to see if the foundations are suitable or not.

Depending on the outcome of that investigation will then determine what plans need to be drawn up. No point getting plans drawn for just a second floor when a grounds up build is required, and likewise no point getting ground up plans drawn if only a second floor is required.

Planning shouldn't be an issue based on the majority of surrounding areas having large extensions and all sailing through without issue.

 

[DB_SamX]

It's just not the foundations though; you'll need a structural engineer to check that your whole ground and first floor can accomodate the increase in load, but agree that the critical item is likely to be foundations. One should be able to do the feasibility calcs for you for a few hundred £.

If it was me, I would get that confirmed first, then get plans drawn up by an architect for planning, and then get the engineer to do the calcs for Building Control.

Note that you are unlikely to get planning unless there is a precedence for other two storey properties on your road.

 

[wnb]

We wanted to do something similar to the op. We dug an inspection hole to the founds and building control came out. We needed the founds under pinned, in addition to this we found part of the external wall was single skinned and would not support the extension. Suddenly the 30k build was 5ok, now were discussing knocking it flat and start from scratch.

 

[LeeUK]

A neighbour had a first floor extension built above a 1970s single story extension about 10 years ago, well part of it. No idea if they underpinned it but I don't think so as they were still living in it while it was done and the outside backed onto their neighbour's property.

 

[Syla5]

Note that you are unlikely to get planning unless there is a precedence for other two storey properties on your road.

Lads of precedence set, out of the 7 houses which have extensions in a street of 5 of them have 2 storey, and all 5 of those added a lot more space then we are interested in doing.

Precedence doesn't guarantee anything I know this, but considering the plot sizes and work in comparison to others, I could see the planning office struggling to come up with any reasons to refuse.