Cracked Glulam beam in new extension :-(

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Good morning all,

This is my first post, though I have "lurked" to diy-not on a number of occasions but never signed up until now in order to ask a question :)

I'm having an extension built to my "shalet" style house, a large garage on the ground floor and a new master bedroom, ensuite and closet upstairs together with a bit of re-modelling of the existing space upstairs. An old flat-rooved dormer window ripped out, and replaced with a pitched roof with a new matching dormer in the new bit too.

An architect has done the drawings and got the job through planning permission/buildings regs with a little help from a structuaral engineer sub-contractor who did the calcs for the roof loading and glulam beams. I went for the "full plans approval" route so the buidlings inspector rubber stamped it before any work began.

The glulam beams have been in position since mid september, and for one reason or another didn't get put in until a gable was up so it had to come back down again to be done correctly (they form a T-piece and each length would have been on a different elevation, duh). All that was specified on the the drawing was the dimensions and positions of the beams, and of a supporting post - there was no detail as to how the beams should join together. The chippies took it upon themselves to decide on something like a normal joist hanger (but larger) would be adequate so got a local fabricator to make one up (this bit was with my say-so). Alas, the bracket would not fit in with the beams already in position (it was kept supported with props in the mean time) so I had to slice an edge off, slide it in to position and weld the edge back on again in-situ... photos make it clear!!

Now, three months on a crack has appeared in the beam, I understand it might be "checking" in which case I can rest easy. I've not spoken to the builder about it yet, next time he's on site I'll show it to him and see how he reacts.

I wonder is it worth getting in touch with a different structural engineer to assess the job and the bracket? I cannot approach the architect (or structural engineer) who originally "designed" it as I cannot stand to work with him after a dispute over the quality of work/deliverables from the SE regarding lack of details/joined up thinking between the pair of them!

My concern is that the chippies, in good faith, took in upon themselves to specify a bracket, and I had my hand in is blessing this off as acceptable - when really the hidden intention of the SE was for me to say there's not enough detail here and to levy another fee to add this detail (he happens to have a side line in glulam design...). I placed my trust in the experience of the chippie/builder and "if big is enough, bigger is better". I don't know if there is any fault with the bracket, the way the beam attaches to the bracket or the overall design on the system. Or even if this cracking is anything to worry about? I have marked on the current length of the crack (about 0.57m) and will be continuing to monitor it very closely indeed!

The photos are taking ages to upload to photobucket - I'll edit the post when they appear

Nozzle
 
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Photos at last:

Firstfloorplan-Glulams.jpg


View 1 Beam-A End-1
Beam_A_End_1.jpg


View 2 Beam-A End-2 (before the wall was knocked down to be replaced with post)
Beam_A_End_2_With_wall.jpg


View 3 Beam-B End-3
Beam_B_End_3.jpg


View 4 Beam-B End-4
How_Beams_meet-without_metalwork.jpg


View 5 General view - New dormer in background, junction of beams to centre-top of picture, trippled supporting post to left side of photo.
General_view_bracket_and_tripple_post_visible.jpg


View 6 Trippled post resting on what was the brick wall (concrete pad in place)
Trippled_post_resting_on_remaineder_of_gable_end.jpg
Trippled_post_supporting_beam_A_End_2.jpg


The cracks that have appeared (currently 57cm to the end):
P1020404.jpg

P1020393.jpg

P1020401.jpg


Also signs of de-lamination
P1020398.jpg

P1020400.jpg
 
Considering the size of that beam, the cracks are relatively tiny, close to a supported end, and probably nothing to worry about.
In any timber structure you'll get the odd bit of wood with a split or crack in it.
 
Any delamination of a glulam beam should be investigated, as should splits near to bearings and connections
 
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Any delamination of a glulam beam should be investigated, as should splits near to bearings and connections

Who do you think is the best trade to investgate - employ another SE or trust the builder?!?
 
Thinking about this again, I wonder if the fittings that were used are the cause of the problem. They're screw-threaded bolts that don't go all the way through. The bracket that the beams sit in as slightly wider than the beam, so with one side done up tightly, and when coming to the other side the bolts are tigthened onto the bracket first but will continue to spin and jack apart the bottom laminar - causing the glue to split and a split along the length of the beam (well, 0.57m)... which at least means the cause is not overloading etc. Hum, there's somthing to think on.. I only noticed it after remving the protective film so may have been there since day dot.
 
An independent structural engineer should really have a look, ask of they have specialist knowledge of glulam or timber beams though.
 
Any delamination of a glulam beam should be investigated, as should splits near to bearings and connections

er, yeh, what he said.

I'd be suprised that a small crack as this would cause any problems on such a large member though. I'm also suprised as to why the builder used coach bolts. As you suspect they are probably the root of the problem. Changing them out for a proper bolt and nut should be too much grief.
 
I think there's no doubt about it, I'm going to have to shell out for a SE to asses it :(

If only it were easy just to replace the coach bolts with threaded bar and studs. Alas the holes in the bracket do not align on each opposite face of the bracket.

I could attempt to drill in-situ but the chances of getting them properly aligned drilling in that position is small, and then there's the problem of having swiss-cheesed the end of the beam by drilling even more holes!

Bracket_as_delivered_needs_modifying_to_fit.jpg




Nozzle
 
Shell out £250 for an opinion? Better off using that money on a drill press and re-drilling the brackets. No matter what he says - you've still got to do the work. Then he'll want to come back for another look when you've done it.
 
I have a drill press, but not a magnetic one for brackets in-situ! Even then - at the moment it has 8 coach bolts each going part way through - changing that for 8 studs/bolts (or 4 and leave some holes) is going to leave less material in "in-there". Ball bags.

Nozzle
 
Refer it back to the builder, who should in turn go back to the original SE and/or manufacturer, you've already paid for this beam, and expect it to work.
A few holes where the coach bolts have been won't cause any issues.
You can drill this with any normal drill, 18v combi and decent hss or cobalt bit.
The beam is currently unloaded?
 
The beam is currently fully loaded, roof on, plasterboard installed ready for painting! (If only I had discovered it sooner...). I recognise the beam can easily be drilled with a handheld - but the bracket is 5 thick mild steel plate, to drill that straight and true with the opposing hole on the other side of the bracket is a big ask!

Nozzle
 
Plenty of measuring and marking should turn out well. I'd use a mag drill which you could hire and that would make an easy job of it. To understand the cracks you have to understand the stresses and load points and the effect it's having on the timber.
I'm surprised threaded rod with nuts and washers wasn't used in the first place!
 

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