Plasterboard/Trusses or Wall Moved?

[00]

Hi all, just seeking some ideas and some experience.

Our 1st floor bedroom has always creaked and cracked about - worse in the wind and worse if the window is open. (past 3 years)

Looking into it is seems that the coving is hiding a gap between the external gable-end wall and the plasterboard. If I push up against the plasterboard, you get the similar cracking sounds.

So the question is the cause of this gap. There is a similar cracking in the coving on the ground floor, but not as bad.

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If I look up in the attic, none of the boards are perfectly in line along that wall, the gap seems to be worse in the middle of the wall probably at most an 8mm gap. It does look like at some point someone has put a few mm of mortar in between the wall and the plasterboard to perhaps bridge this gap and it may be that this has all come off exposing this gap.

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Other concerns are that there are vertical cracks in the internal blocks (not on external brick that I can see but then I can't get that high up). max 4mm.

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There are a couple of conifers (one recently felled, one 2m English laurel) within 2 to 3m of this wall. Clay soil.

Any thoughts on best approach. I could take down the plasterboard and put new up and make it fit better which I guess would stop the movement at the end?
I am about to put in celotex insulation at pitch level which would reduce the airflow (perhaps this makes symptoms worse).
is it worth getting Structural Engineer in to check foundations and catch any subsidence early?

Appreciate any thoughts. See pics below

 

[wrightwoodwork]

Just looking at your pictures there is a couple of issues I notice the distance the first ceiling joist to the gable wall is too great. The plasterboard sheet can fly past the joist 50mm but not 200mm. If you fix a timber to the wall with a bit of dpc between the timber and block then screw the sheets form below to the timber it will stop the squeaks as the plasterboard will not be moving independently of the wall. The stackered gaps of the plasterboard are of no real concern

The second issue that is wrong the gable tie has been fitted incorrectly. The L should be into the cavity and pulled back tight to the outer face of the internal block, then on the inside there should be noggings from the wall to the first truss to stop the L of the strap going into the cavity then there should be noggings in each bay for the the rest of the strap and fixed with twist nails and fixed to at least 3 trusses.
Also has the roof been adequately braced. If it has not the roof will creek about. I guess it's a fairly new house I would get the builder to sort the gable ties and if you know any joiners ask them if the bracing for the roof is ok.

 

[wrightwoodwork]

I would imagine the foundations are ok when a house is first built in the first couple of years it settles and sometimes you can get little stress fractures as long as you can't see cracks on the outside wall then I wouldn't worry to much I think the problem is more to do with the roof not being properly tied to the gable. I would check the rest of the gable restraints and the wall plates is tied down to the walls and truss clips have been used

 

[00]

Thanks for the thoughts wrightwoodwork.

Just been up to measure and you are right the gap on this end is between 120mm to 150mm from last joist to wall. Opposite end has no similar problems and this is <100mm. The issue is worse where the gap is larger. Fitting timber to the wall is a great idea. What would you suggest 45x70 all the way along using packing pieces to sort out undulations in blockwork and use 100mm CSK concrete screws or other? I guess I would have to screw in at an angle to avoid joist but just a single row of screws should be enough all the way along, 1 every 500mm?

The strapping & bracing actually I am in the process of doing (alongside the rigid rafter insulation work). The SE indicated on drawings that face-fitting strap is ok for a retrofit so that is what I did. You cant see from that picture but the gable strap is screwed to noggins that are tight between the 3 end trusses and there is a packer piece between the wall and the last truss. There are 11 of these at each gable end < 2m distance. There are a few more braces to put in. This has only just been done (last 6 months), so the building has had 50 years to move about with only 2 lateral braces at ceiling level (that actually go through the internal block which you can see in pic3). A couple of the trusses are visibly bent (in the middle) but mostly seem to have aged reasonably well

Thanks again

 

[tony1851]

If there are only cracks in the internal blockwork - and none in the outer brickwork - it is usually not a problem. Those lightweight aerated concrete blocks are prone to shrinkage cracking, but it's not anything to worry about.

 

[00]

I would imagine the foundations are ok when a house is first built in the first couple of years it settles and sometimes you can get little stress fractures as long as you can't see cracks on the outside wall then I wouldn't worry to much I think the problem is more to do with the roof not being properly tied to the gable. I would check the rest of the gable restraints and the wall plates is tied down to the walls and truss clips have been used

Truss clips haven't been used, it looks as if skew nailing was used to attach rafters to wall plate although it is difficult to see as can't get that close and not 100% sure I know what I'm looking for.

I'm not sure how I can see how the wallplate is attached to the wall, what would have been normal on a 1960s build?

Here are some pics which might help. Thanks again!

closeup of join rafter to joist
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looking over the wall
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further away
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[00]

If there are only cracks in the internal blockwork - and none in the outer brickwork - it is usually not a problem. Those lightweight aerated concrete blocks are prone to shrinkage cracking, but it's not anything to worry about.

Thanks tony. I probably need to get up there or get some binoculars and have a proper look to check the external but nothing obvious.

There are lots of gaps and dodgy mortar work around those blocks. Is it worth doing a bit of repointing on these and perhaps in the larger cracks also? or best to leave alone.

A couple of the blocks sound like they are loose if I put pressure on (slight hollow sound if I thump it gently). Most seem solid apart from a couple of the top ones. This was the other reason I thought perhaps some repointing would be useful.

 

[wrightwoodwork]

45 x 70 and concrete screws you suggest fixed at 500 mm but no more than 600 mm. I would strongly advise to get the rest of the bracing done quickly to give rigidity to the roof quickly. The roof has to be all tied together to reach it strength I know it can be a pain when insulating but I would worry more about doing the braves than the insulation. Also don't know if I've picked up wrong are you planning to insulate the rafters or the ceiling. There is no advantage to insulating the rafters

 

[00]

45 x 70 and concrete screws you suggest fixed at 500 mm but no more than 600 mm. I would strongly advise to get the rest of the bracing done quickly to give rigidity to the quickly. The roof has to be all tied together to reach it strength I know it can be a pain when insulating but I would worry more about doing the braves than the insulation. Also don't know if I've picked up wrong are you planning to insulate the rafters or the ceiling. There is no advantage to insulating the rafters

Great thanks for the reassurance of the plasterboard fixing technique. More wood and fixings to buy but saved me the price of a Structural Engineer fee!

Yeah I'm Insulating between and below the rafters with celotex (ridge and eaves ventilation getting installed this week). Many reasons why but mainly uses less space, easier to board out, lots of downlighters on 1st floor, lots of future work in the attic all at ceiling level so nice no insulation in the way and other utilities that benefit from insulated roofspace (computer equipment, ventilation etc).

 

[wrightwoodwork]

OK I see now makes sense it will be toasty on the attic with them computer cables