Detached Dormer Roof - Dip in roof caused by joist not installed correctly

weeslip

We went sale agreed on a detached dormer last week. I had my engineer in on Friday. He gave the place a clean bill of health with one sizeable exception. The house has decent square footage and an L shape to the roof. All of this leads to a problem I'm told is common in dormers. The roof has a slight dip in the 'valley' where the two roofs meet. From inside the attic, it's pretty obvious what's going on.

The photo shows where the joist has started to slip. The engineer suggested a steel pylon down through the roof/partition walls to a load-bearing wall that could then be used to release the pressure. My dad has construction experience and has suggested that a couple of other options might be worth looking at that are less intrusive. Primarily bracing the beams within the attic or using a door frame directly below the joint to distribute the load.

I'm getting an engineer/roof expert in but it will be later in the week/next week and I'm interested to see if anyone has had similiar issues.

It seems like this will be a blocker for getting mortage approval. It's a small town so I know the vendor. I'm hoping we can come to an agreement and that this can be handled in a reasonable manner so any suggestions very welcome.

Mellor

What kind of engineer did you have do that first inspection?

That not a joist, it's a rafter. That might seem like semantics, but I'd expect the person giving to at the very least know the difference.

And it's not "slipping". It's bearing points are either end, out of view of the photo. The rafter is probably strong enough for the span (this has to be checked), the issue is that the lap joint is opening.

The solution could be a simple as repairing the joint. I look at the before I started dropping vertical supports to the structure . Did the engineer really suggest a pylon? I assume he actually meant a post. The issue with a vertical support is that load bearing walls are most likely at ground floor, plus is not guaranteed that that's a wall below this joint.

pagan22

span 3 9by 3 bolted together from wallplate of roo f to load bearing wall and then prop from the 9by 3 [which in essence is a beam now 9by6 or add another9by 2 to make it a 9by 8]to the underside of the bodged hip rafter

😁

sydthebeat

looks like a valley rafter?

it needs to be propped directly below that (guntered) join, and splinted as well with metal plates and at least 3 M5 bolts both sides

grimeire

Yeah that's definitely a valley/internal hip rafter. That is supporting the weight of all the jack rafters cut into it.

Why the heck did they join it? It doesn't even look like that long of a span. They should of used a better joint than a halfing joint and definitely braced it whether there was a joint on that rafter or not.

I'd see if there is something you can put the load on underneath it. There might be a wall you can brace and prop it off.