Roof strap conundrum

[Roger440]

Im doing some work on the roof of my house.

 

However, its come to light that there appears to be nothing holding the roof down on the extension. There were a couple of straps nailed to a rafter and down into the wall plate. Which clearly isnt much use when the nails are in the vertical plane! They just pulled off by hand.

 

The work has introduced ventilation via the eaves that was previously blocked off. Which was causing some condensation isues unsurprisingly.

 

The house is reasonably exposed, ive introduced ventilation, therefore wind into the roof, and theres little holding it down. Which is sub optimal.

 

The front half of the house has 2 massive purlins that are embeded into 2 ft thick stone gables. So theres no realistic risk of the roof being pulled upwards.

 

The extension roof is at 90 degrees to the original part and all tied in and nailed together.

 

Ive been up into the gable end of the extension, put a strap on off the ridge beam onto the gable wall, and, addtionally, the end rafter has diaganols down to the ceiling joist. Ive bolted these to the gable wall too. 

 

So, im happy the gable end is pretty secure, the other end is well tied into the existing roof.

 

Its the bit in the middle thats troubling me. The wall plate is on the outer leaf with birdsmouth to clear the inner leaf. No straps to be seen. My current thougts for retrospective installation is on the inside wall and screw to rafter . The ceiling has the 45 degree slopy bit on the inside so can do all of it from inside.

 

However, as one might imagine, this involves making a mess of the bedroom, and so there is pressure to not do so.

 

Am i over worrying?

 

The roof is quite lightweight, 75mm rafter and composite roof tiles.

 

Thoughts please?

[Mr Punter]

Is the wall plate strapped down?  If so, you may only need a truss clip or structural screw to fix each rafter / truss to the wall plate.

[Roger440]

2 hours ago, Mr Punter said:

Is the wall plate strapped down?  If so, you may only need a truss clip or structural screw to fix each rafter / truss to the wall plate.

No, its not. Thats my issue.

 

 

[ETC]

Strap the wall plate down with 30mmx5mmx1000mm long wall plate straps at maximum 2.0m centres.

Install gable and ceiling straps at the same centres across three rafters/ceiling joists.

[Roger440]

1 hour ago, ETC said:

Strap the wall plate down with 30mmx5mmx1000mm long wall plate straps at maximum 2.0m centres.

Install gable and ceiling straps at the same centres across three rafters/ceiling joists.

 

I may not have explained myself well.

 

The house is already built, this bit 40 years ago. 

 

I cant access the wall plate, at least not without removing some roof, and even then, it would have to be on the outside of the wall.

 

Yes, its true i could see the top of the wall plate whilst doing the work, but that didnt really help as id still have the issue of the vertical part of the strap being visible.

[Nickfromwales]

Looks like you'll end up popping a few tiles off, and then drilling down with a 600mm sds bit at 10mm dia, and then resin bolting the wall pate down.

 

You know the only other option is to cut some slices out of the interior......

[Gus Potter]

On 13/09/2025 at 15:38, Roger440 said:

However, its come to light that there appears to be nothing holding the roof down on the extension.

 

On 13/09/2025 at 15:38, Roger440 said:

The house is reasonably exposed

Ok you say reasonably exposed. The vulnerable points are the eaves, verges and roof ridge. Say you don't live in the north of Scotland, Islands. Very quick sum and to cut a lot of the maths out. The wind load uplift will be about 100 - 150 kg/ m^2 (working load on a 50 year return period) at the exposed edges of the roof. But as you move towards the middle of the roof it will be less as an area average., the design codes call this roughly "non simulataneous action" as the wind is made up of vortices, big and small, that don't act on a roof evenly. 

 

The original part of the house is probably ok?  How old is it, if it's been ok up till now then is that ok? 

 

Think about this another way. On new build stuff as an SE I design to the codes but when assessing existing historic houses we need to be pragmatic. 

 

If the wind gets up it often blows the tiles / slates off at the edges of the roof; verges, eaves or around chimney stacks. There used to be guidance on this in the old building codes. 

 

On 13/09/2025 at 15:38, Roger440 said:

The front half of the house has 2 massive purlins that are embeded into 2 ft thick stone gables. So theres no realistic risk of the roof being pulled upwards.

Yes, but the quality of roof tiling workmanship would have been good. The key here is to not let tiles get blown off in the first place as as soon as that happens you lose the dead weight resisting the wind uplift. And here the quality of the extension roof needs to be examined.

 

This is obvious.. if you prevent the tiles / slates getting blown off at the edges of the roof and thus prevent progressive peal back of the tiles / slates then you, maintain the dead weight which resists the uplift. Your big purlins will not be contributing much unless the ends are well strapped down to the gables. 

 

Go back to basics and think.. what has been changed in terms of wind loading. The extension is the obvious thing.