Replacing rotten wood lintel in limestone building

[rosbif]

I'm restoring a building (~200 years old, limestone walls, lime mortar, with what looks like 150 years of bodging...... :? ). Over one of the windows is a wooden lintel which is wormy and bending (and too small IMHO). I've replaced lintels in brick buildings before, but I'm a little concerned about the integrity of the wall above the lintel, where I'd put the strongboys on acro props to hold it up while I replace the lintel. Normally, I'd have a strongboy on each side (left & right) of the window and expect the brick course between to hold together. The area that I've exposed so far is crumbly and some small stones are already loose. Any suggestions on how to approach this? I was thinking maybe a series of thin(-ish) planks across the top of the lintel to hold the stones in place.

 

[Penners]

The usual way of dealing with this problem is to use what are often called "needles". I've no idea whether this is the same thing as what you call "strongboys" (but that expression should bring a flush to the cheeks of our female forum members. :wink: ).

Stones (or bricks, as appropriate) are knocked out at intervals immediately above the lintel that you want to replace, and stout timbers are passed through the wall at these points, projecting a foot or so each side. These needles are then supported on acrow props each side of the wall. Then, when you remove the lintel, the needles hold up the masonry until you install the new one.

The number and spacing of the needles must obviously be a matter for your judgement, depending on the size of the stones in your wall, and the integrity of the masonry.

When all is said and done, however, if you've misjudged the spacing of the needles a bit, the worst that's likely to happen is that you lose a stone or two here and there.

Your nom de plume is interesting. Are you in France?

 

[rosbif]

Non, la plume de ma tante est sur la table.
It's an old nickname

So, coming back to needles - could I use scaffold poles for this? - my thinking being that the holes in the walls would be smaller

 

[chuckey]

I've got this on two upstairs barn windows, rock'n rubble construction with the rafters sitting on the rubble.
I think the first step is to remove any rattlingly loose stones, they aren't taking any load and will only add to the pile of rubble if it all goes pear shaped. If you own your own strongboys, set them to the height of the top of the wood (one every 2') and attempt to just beat them into the wood, adjusting their feet to keep them upright. If the wood is that rotten and worm eaten it should turn into dust as you go. The stones are just jammed there in the dust and muck :roll: .
Whats the mortar like?, on mine is missing or at least virtual, so I shall rake out a band about 18" high and a foot longer each side then my windows (3" deep) then repoint with a very hard cement mortar (1:3, cement/ sharp sand). let it go off and it will hold the bottom layer of stones in place.
In general rock'n rubble walls have "throughs" here and there or even in whole courses. These are stones that run right through the wall, so the inner skin will be partially supported on these.
Whoops! Just re-read your letter, exactly what sort of construction does your building have. The above is for a Yorkshire dales cottage, two skins of rock filled with rubbish, rotten wooden lintels on inside and limestone lintels on outside. An added bit of excitement is that when the wooden lintels are removed a bit of the rubble infill make a bid for freedom, so look out for your toes!
Frank

 

[MdB]

Strongboys:

 

[Nemesis]

so I shall rake out a band about 18" high and a foot longer each side then my windows (3" deep) then repoint with a very hard cement mortar (1:3, cement/ sharp sand).

Sigh.

 

[Andrew Bodenham]

I've seen various approaches used in lintel replacement, both on my own house and on clients properties. Unless the aperture is very wide (say over 4') you can often proceed without using any temporary support. If the original lintel has sagged or compressed then there will be a triangle of displaced masonry above it, and this should be unbuilt up to a point where the "good" masonry has formed a self-supporting arch above the damaged area. The alternative " builders" approach is simply to cut or knock out the old lintel and see how much falls down.

Once you've put your new lintel in place it would be a good idea to create a water deflecting barier on top of it to shed water running down the inside of the wall outwards. I've used lead sheet for this purpose, suitably dressed and bedded with a fall to the face of the lintel. If you're using a timber lintel the lead could be dressed over the exposed face and finished with a drip-off detail to protect the wood.

Then it's simply a matter of building up the stonework on top of the new lintel, using lime mortar (of course) and filling the core with small loose stuff as you go. In this way you get a very solid repair, and the absence of props, needles etc makes access so much easier.

You will have to judge the structural situation, or seek expert advice if you do not feel confident.

 

[Penners]

could I use scaffold poles for this? - my thinking being that the holes in the walls would be smaller

Zut alors... I suppose so. The only possible downside of a scaffold pole, as compared with a piece of timber, is that there's no flat surface for the masonry to rest on. However, it's down to your judgement as to how important you think that will be.

 

[Penners]

Strongboys:

My wife's very disappointed. She was hoping for

 

[FamilyWiggs]

I wondered what you looked like Penners! :shock:

 

[Penners]

Actually that's my older brother - usually referred to in the family as "The Ugly One". Poor chap suffers from being compared with me.


Also referred to by decent Photoshop experts as "The Cardboard Cutout One".

 

[rosbif]

So, after some further demolition, this weekend, here's a picture of the inside:

The wooden beam at the bottom appears to be relatively new, and is some kind of softwood I think. The bendy beam above is the inside lintel, unconnected to the outside lintel, which is hidden from view behind the bottom beam. The wall is a solid wall (no cavity) about 0.5m thick. At some stage, original joists (the bendy ones ,of course, on the left) have had new (softwood) joists sistered to them. The joists (sometimes the old one, sometimes the new ones, seems entirely random) rest on the bendy beam and/or some brickwork/concrete ("sigh", to pre-empt Nemesis..). The bendy beam is "supported" (I use that word with some trepidation...), by the brick, with a couple of layers of slate hammered in, and by the enormous (at least 25mmx25mm...) three blocks of wood.
I think I'll go count my acro props........

 

[Penners]

Is the old, rotten, bendy beam actually supporting structural masonry? It's a bit difficult to tell from the photo whether the few visible bricks resting on it are structural, or just packers.

If it is supporting structural masonry, then - given that you have a hefty new softwood lintel over the window, is it really worth replacing the old bendy job? Wouldn't it be better to build up new brickwork directly on to the softwood lintel (replacing those small supporting studs) and do away with the old, bendy lintel altogether?

 

[rosbif]

Here's a view from above after I lifted the end floorboards:

You'll see that the joists run across the bendy beam into the wall, but there is very little of the joist into the wall - the bendy beam is "supporting" them.
This picture better shows the (internal) bay that the window sits in - the bendy beam spans the bay.
My plan is to remove the bendy beam, pack above the softwood beam to support the joists properly and then fill in any voids with stone and hempcrete.
What you can't see from any of these pics is the external lintel (well, it was raining....) which is the thing that I started with trying to replace. I need to stabilise all this interior stuff before doing that.

 

[chuckey]

I see the builder did a "proper job" then! :shock:
Frank

 

[Penners]

OK - I clearly got the wrong end of the stick!

 

[middi]

Go to the nearest scrapyard an collect a length of 8/10 mm thick+, at least 4 inches deep scrap angle iron, " grove" it into the external masonary and hold up with a couple of props.

Use another couple of props combined with an appropriate length of 4x4 or a couple of short csaffoldboards ( one above the other) to hold the internal floor.

Remove inner lintel and replace with new oak lintel to span under the floor joists and as far as the edge of the angle iron under the internal face of the wall.

Remove external contraption which you erected earlier and make good the external wall as required.

That should work.

 

[Penners]

He sounds as though he's done it before, doesn't he? :wink:

(You can bet he has. Middi knows this stuff.)

 

[middi]

You must be right Penners, I am still alive ( If only just, at times). :wink:

 

[Penners]

To misquote René Descartes:

I post, therefore I am.