Lintel replacement advice - low load bearing

[hexdex]

Hi all.

OK, so I'm in the middle of a major bathroom refit and whilst examining the external plaster (lath and plaster), I decided it was no way strong enough or well enough constructed for full wall tiles, so off it all came today. One nasty shock was that the window lintel had been seriously attacked by woodworm at some point and needs replacing. Luckily all other timbers seem unaffected.

I'm just not sure what's needed. As you can hopefully see in the pictures, it's not really a main load bearer. Just three upstairs floor joists rest on it as the house is an old traditional Scottish dorma cottage. This is something I have absolutely no experience of, but as it's a low load old timber lintel I'm sure I can do it myself given some advice on what type of lintel I need.

I also presume I just need to jack support the three joists above as I replace the lintel? It's the double stacked lintels on the inside that are damaged.

Thanks.

 

[KenGMac]

hexdex, good evening.

If you are sure that it is only the inner set of lintels that are affected then I would suggest you support the upper floor then remove the damaged so called [in some places] the timber safe Lintels

As for replacement, most common and easiest option is to source Concrete Lintels or a single Concrete lintel of suitable depth, suggest you opt for a couple of thin Lintels, they are easier to lift into position compared to one large lump of Concrete.

Simply Google Concrete lintels and then make a decision on depth and span, if the depth comes up short, then simply pack between the upper floor joists and the upper surface of the lintel with something like Slate, this material simply will not deform under a load.

You may wish to consider treating the remaining external lintels with wood worm treatment, I have reservations about that stuff, and also at the same time spread some "Deep Kill" to assist in preventing wood rot from affecting the Timber.

Ken.

 

[hexdex]

Thanks Ken that was good advice and much appreciated. I am a little surprised that no other timber appears affected, but there is nothing that is detectable. It's especially surprising as those beams are riddled right through. Maybe different materials? Then again I have no idea what timber treatment was used 130 years ago if any!

Regarding the support of existing upstairs joists, can I ask what's best practice....just increase support till they just start to raise so I can get the support under? And would I set the lintels into a mortar bed?

Thanks again.

 

[KenGMac]

hexdex, good evening again.

Suggest that you spread the load of the props using heavy battens, heavier the better spread over several floor joists.

Apply the pressure from the props, again using a spreader large beam to provide support to the upper floor joists, all you need to do is to take the weight of the upper floor joists, lifting them is a potential problem in that the wall in the room above. probably Plaster can be stressed by over tightening of the props.

Cut out the defective inner lintels, any quick way you can, remember to hoover up as much dust as you can in case there are live beetle larva still surviving???

As for insertion of the new Concrete beams, set them on as before Slate and a layer of Sand and cement, pack [if needed] between the joists and the new Concrete lintels with as before Slate

 

[hexdex]

Good man Ken. Solid, sensible advice which makes perfect sense. Much appreciated.