When to replace a lintel

[greeny]

I don't knwo if I should be worried and planning a lintel replacement or not !

The front part of the house was built c1600 ish. and is built of riverstone (granite mostly) and lime mortar.

The lintels I am worried about are over the front door. I can only see a little of them on the inside of the front door (there is another 15" of wall to the front of the house). The outside of the house has been rendered and painted at some point, so nothing to see there. I estimate that there are 3 intels (if they are all wooden all the way through and of the same size as the ones I can see). I can see about a 2"wide section of the first lintel and it has worm holes all over it, the second lintel behind it I can just see and appear to have beetle holes too, the third lintel I am just assuming exists, but I have not come accross a single stone lintel in theis place yet, so I doubt I'll be that lucky !

Is there any objective way of assesing if I need to replce them. If I have to expose them any more I'll have to strip the ceiling down from under them (I have had the floorboard up upstairs, can't see anything from there).

What is the best way to proceed ?

Thanks

 

[Moneypit]

This will be a tricky one for you I think. Unless you expose enough of the timber you won't be able to make much of a judgement. However, don't be too pessimistic, your lintels will be able to suffer a lot of boring insect attack without losing a significant amount of strength. This coupled with the fact that the section size put in was probably far in excess of that which was structurally required. Also bear in mind that your lintels are only having to support the triangle of masonry above them.

Any professional advice you sought would probably err on the side of caution and suggest replacement or treatment/strengthening.

You haven't said whether the attack is active or historic. If historic then, unless your timbers are teetering on the verge of collapse, you probably have little to worry about.

 

[middi]

Drill one or two exploratory holes using a small drill bit, use a penknife or drive to 2mm dia. small nail into what you can see of the wood, this will determine how sound the wood is. Don't concern yourself if the first 5 or 10 mm of the wood is quite "soft" it would be quite normal, as long as the wood becomes "harder" and more stable beyond the " skin" stage there is nothing to worry about.

You need to get a clear access to the wood you want to test in this manner.

As you can appreciate this is not a scientific test but one which, coupled with experience, is the next best thing.

 

[Tom]

Just to give you a bit of confidence, we suffered a well-known company's largest domestic claim ever for Death Watch Beetle (hence my name on here!). Although our house was bouncing with them in May every year, the damage they'd done over many, many years was, in proportion to the wood in the house, quite small. As Middi has said, the outer portion of the wood could well be totally shot and be quite alarming, while the centre could be as hard as steel. Indeed, we had wood just like that, that we have actually burnt drlls out on trying to drill into it!! Thinner sections of wood are more at risk than larger pieces. For example, our joists are 8" x 7" and while the outer sections are eaten all over, the centre is rock solid. Our biggest problem was in the mortice and tenons joints, where the wood had been eaten through and the joists were about to fall out!! I still have some of the wood which was removed and will try to post a picture of the cross-section of it later for you.

Hope this helps a little.

Jaqy

 

[greeny]

Thanks for the responses. I am not quite so worried now, worst case seems to be an embarasing pile of rubble on the pavemant and the neighbours talking! I am going to take middi's advice, I'll expose some more of the timber, just enough so I can get at it and test to see just how hard it is. The DWB is definatly still active, I have heard them this year, but if you turn the radio up a bit you can't hear them ! I'll let you know what I find.
Thanks

 

[greeny]

Hi,
Well I decided to have a proper look, and it looks just terrible.
View attachment 1


Now although it does look terrible, the lintel on the right in the second picture, where it is thinest seems to be down to the heart wood, and I cant get my stanly knife blade into it more then about 1mm if that, most of the rest I can get it in about 5-8mm. where it is sponge it goes further but still allways hits solid wood in about 15mm or so. Clearly however a good percentage of the original wood is dust. On the plus side the mortar in the masonry above it is good. There is at least one further lintel to the right of these, I can only see a little of it, but from poking it with a long screwdriver it feels in better condition than the one I can see well.

Anyone have an opinion, should I replace or will it do another 50 years (it has done 400 so far!).

Thanks

 

[middi]

If you had exposed those beams 50 years ago they would have looked no different, I also bet that if you inspect them in another 50 years there would be little change, nevertheless, you could always install a very thick metal bar between the two beams to help maintain the above masonary stabilsed in case one of the beams decide to give up the ghost in 100/200 years time.

 

[Tom]

Here you go, Greeny, I promised you some pics. I hope they help to stop you panicking TOO much

You can see how the outer looks horrific but that really it's only skin deep and the inside is as hard as steel

Jaqy

 

[greeny]

Thanks for the pics. I think I'll stop worrying now. they will probably outlast me by the odd century