Structural Survey

[Gad-Westy]

We are hoping to replace a flat roof on our extension with a pitched one (see my other thread). But before we do this, I'd like reassurance that the extension is structurally sound. Partly this is because we live on a very steep hill, and everything in the extension seems to be on the piss (though sloping in all directions, I think it was just bodged but I want to check) but also we get a lot of cracks in plaster work that might be nothing or might be something, I don't know.

So I'm a bit out of my depth with this but I'd like a professional opinion. What can I expect from getting a structural survey done? What can they do or measure to determine if there are are any issues to address?

[C Lee Farquar]

I would use a Structural Engineer. They'll tell you what's wrong and spec the changes you want to make.

[Gad-Westy]

C Lee Farquar said:

I would use a Structural Engineer. They'll tell you what's wrong and spec the changes you want to make.

Thanks. Will look into that option. What can they physically check out of interest?

[Alucidnation]

I doubt a structural engineer will want to get his hands dirty so you will either have to expose what is required yourself, or get a handyman/builder to do it.

[Gad-Westy]

Just to update this and maybe some further questions.

We had a non-intrusive survey carried out by a local structural engineer and got the report last week.

among some other minor issues, the gist of the report is that there has been historical movement/settlement but no sign of recent movement.

Whilst that's sort of encouraging, it doesn't necessarily help as the goal is to put a pitched roof on so I'm concerned that chucking a load of extra weight on top is going to cause issues.

So my gut feeling is that we now need to get some underpinning work carried out to offer some reassurance to us and any potential buyer if we were to ever sell.

Would I be correct in saying that next thing to do would be to start speaking with some underpinning specialists? Access is a bit limited so I don't think this would be a bread and butter job.

Or do we need to get plans drawn up for roof first and go from there?

[C Lee Farquar]

A structural engineer would calculate the new loads and advise what underpinning, if any, were required.

You will pay through the nose if you use an underpinning 'specialist'

90% of the work is digging big holes, usually by hand.

[Gad-Westy]

C Lee Farquar said:

A structural engineer would calculate the new loads and advise what underpinning, if any, were required.

You will pay through the nose if you use an underpinning 'specialist'

90% of the work is digging big holes, usually by hand.

So I guess you're saying:

1. Get plans drawn up for roof structure that defines foundation loading required
2. Get builder to dig holes and amend foundations as required
3. Crack on

Only issue I forsee is access for digging. Down the side of the house is a concrete path between our house and next door's garage. It's only 16" wide. You can walk down it, but crab style. Much of that wall is garage though so I guess that could be accessed by digging up the garage floor. The rest, I don't know.

[Lotobear]

A pitched roof only (as opposed to an additional storey) is not going to result in a seismic shift in the foundation loads. If you describe the roof construction, and finish, you have in mind with your engineer he will be able to calculate the new loads, from his load tables, without you having to spend money on detailed design.

Expose the existing foundation in a number of locations around the existing building, down to bearing material, by digging some trial holes and ask your engineer to inspect. From this, and the roof design information, he will be able to calculate whether the existing founds will accept the additional load.

..you may just be in luck.

[Gad-Westy]

Lotobear said:

A pitched roof only (as opposed to an additional storey) is not going to result in a seismic shift in the foundation loads. If you describe the roof construction, and finish, you have in mind with your engineer he will be able to calculate the new loads, from his load tables, without you having to spend money on detailed design.

Expose the existing foundation in a number of locations around the existing building, down to bearing material, by digging some trial holes and ask your engineer to inspect. From this, and the roof design information, he will be able to calculate whether the existing founds will accept the additional load.

..you may just be in luck.

Cheers. As you may have guessed I'm a little out of my depth here. My concern is that if the building has shifted/settled historically, does that not imply that the foundations were at best borderline to start with? Or is there more to it than that?

[Lotobear]

Not necessarily, it could have been initial settlement or settlement as a result of a cause which has since been resolved (leaking drains or similar).

You need to do the investigations as per my suggestion in order to be properly informed.

[Little Lofty]

OP I think you are local to me? I’ve just done similar to house in Harlow Green. Building inspector wasn’t bothered about the extra load and we didn’t get planning permission, although that’s maybe because I didn’t officially ask for it. The building inspectors in Gateshead are great and I’m sure they would be happy to take a look at it for you, or at the very least give advice over the phone.

[Gad-Westy]

Little Lofty said:

OP I think you are local to me? I’ve just done similar to house in Harlow Green. Building inspector wasn’t bothered about the extra load and we didn’t get planning permission, although that’s maybe because I didn’t officially ask for it. The building inspectors in Gateshead are great and I’m sure they would be happy to take a look at it for you, or at the very least give advice over the phone.

Very close yes. We're Low Fell. Steep hill and an extension built by Homer Simpson.

Thanks for the tip off. I'll make contact with the building inspectors and see where we go next.

[Gad-Westy]

Lotobear said:

Not necessarily, it could have been initial settlement or settlement as a result of a cause which has since been resolved (leaking drains or similar).

You need to do the investigations as per my suggestion in order to be properly informed.

Many thanks. I'll update as we progress.

[Lotobear]

Christ, I used to live in Low fell - Church Road!!

Talk about small world, I though you were from darn sarf

[Little Lofty]

Lotobear said:

Christ, I used to live in Low fell - Church Road!!

Talk about small world, I though you were from darn sarf

I’ve been working on Primrose Hill today, just off Church Road

[Little Lofty]

Gad-Westy said:

Very close yes. We're Low Fell. Steep hill and an extension built by Homer Simpson.

Thanks for the tip off. I'll make contact with the building inspectors and see where we go next.

This is the one I done on Waverly road, it had an existing flat roof on the extension above the garage, so we pitched it, and retiled the whole roof to match.(sorry not a great photo of the roof)

[Gad-Westy]

Little Lofty said:

Gad-Westy said:

Very close yes. We're Low Fell. Steep hill and an extension built by Homer Simpson.

Thanks for the tip off. I'll make contact with the building inspectors and see where we go next.

This is the one I done on Waverly road, it had an existing flat roof on the extension above the garage, so we pitched it, and retiled the whole roof to match.(sorry not a great photo of the roof)

That looks very similar to the scope of work I'm looking at. In our case, the extensions is set back a foot or so from the front wall and built slightly lower so roof line won't join but I'm still considering getting main roof re-tiled at the same time to get a matching look and it's a bit shabby.

Did you do this yourself or a builder? Fishing for recommendations...

[Little Lofty]

I bought that house to renovate and resell, I’m a joiner but just project manage now. The lads who work with me are all subbies, I’m not sure if they would take on your job but I could ask. Pitching a roof doesn’t sound like a big job but you will need joiners, roofers, bricklayers, and possibly plasterers and an electrician. I estimated that to pitch the roof on Waverley cost me over £10k.

[ian_uk1975]

C Lee Farquar said:

A structural engineer would calculate the new loads and advise what underpinning, if any, were required.

Exactly this. Would be worth having a chat with a couple of builders and structural engineers first to get their view on whether a structural engineer needs to look at it, or not. Site visits and drawings aren't cheap, so you don't want to pay for something you don't need.

[Gad-Westy]

Little Lofty said:

I bought that house to renovate and resell, I’m a joiner but just project manage now. The lads who work with me are all subbies, I’m not sure if they would take on your job but I could ask. Pitching a roof doesn’t sound like a big job but you will need joiners, roofers, bricklayers, and possibly plasterers and an electrician. I estimated that to pitch the roof on Waverley cost me over £10k.

Thanks. Good to know.