Historic Brick Load Bearing Walls with Rotted Out Wood Strip

[nwong]

Encountered a 2" thick strip of wood within a 2-wythe bonded brick wall (party wall) right above basement floor level(3 Story Above). Basically, the brick wall was constructed to a certain height, a 2" wood board was placed down and then the construction of brick continued on top of this wood board. The wood is all the way thru the wall. I've heard of this before...does anyone know the purpose and/or have heard of a tried/true technique to shim/repair/replace?

Highly appreciated.

 

[JAE]

Are you sure the wood is continuous down the length of the wall or is it an old window/door sill board that was left in place and the previous opening filled in with brick?

 

[SkiisAndBikes]

nwong,

I have similar horizontal wood strips, laid flat and embedded within the walls of my house. The walls of my house are 2-1/2 ft. thick fieldstone so the wood strips do not continue through the entire thickness of the wall. The wood strips are on the interior face of the walls and are spaced every 2 or 3 ft vertically. Their purpose is for use as nailers for the interior wall construction, typically rough sawn 2x4's covered with lathe and plaster.

 

[SkiisAndBikes]

One more thing ... to answer your question ... If the wood was deteriorating, I would consider phased removal of the wood, in possibly 2' long strips. The gap could then be grouted, allowing sufficient time for the grout to achieve it's required strength before continuing on to the next, adjacent strip. Very similar procedure to that for residential underpinning. Likely further investigation and a couple of small test openings required to fully understand the construction (i.e. are there metal anchors embedded, one strip of wood full width or two smaller strips, etc...) and develop repair procedures.

 

[nwong]

I think it may be some type of nailer as well. It is the entire length of the party wall and the sections I checked was all the way through to the neighbor's side.

Phased removal defintely does sound like the proper approach. For added protection during the phased reapir process, I was thinking of installing a few steel shim packs every 2' and then phase the removal and grouting of the wood strip area every in thirds. Repair 2' strip every 6ft apart and then repeat the process two more times.

To add complexity, the neighbor side, who has been uncooperative in the rehabiliation (opp side of wall), is furred and finished. We have access to only one side.

Many Thanks for the Responses

 

[dik]

You might want to confirm the depth of this strip it should only be approx 1" x 2" or 3". I seem to recall these referred to as a 'groin' (as opposed to a groin vault, etc.) and they were generally used as nailing strips. If through the wall, then as suggested, remove a portion and fill with masonry grout. Be careful not to use a regular portland cement grout. The grout should provide sufficient bearing but should deform 'plastically'.

Dik

 

[SkiisAndBikes]

Here's a question/thought for discussion related to Dik's response. I'm interested in others viewpoints.

If the depth of the wood strips were only partially through the depth of the wall, I fully agree that masonry grout, with similar properties to the existing mortar, be used. However, if as suggested the wood strip is the full depth of the wall, would the choice of grout become less important, i.e. why could one not consider a hard, non-shrink grout or portland cement grout? Through the depth of the wall at the repair locations, there would not be any differential material properties to create hard points. Comments/thoughts?

 

[dik]

You want to replace historic mortar with material that closely mimics the existing wall. Early mortars relied on hydraulic properties caused by impurities in the lime and one of the skills of a master mason was to know how to source proper materials. Use of improper materials leads to problems (maybe several decades later)with the lime leaching out of the mortar, leaving sand and a wall failure. Use of Portland cement can lead to a very hard mortar that does not have the proper characteristics. With uneven loading, it can cause cracking to form due to the higher strength. The object is to be able to remove mortar that is softer (for repairs) and not damage the brickwork/stonework.

Check for my article on Sliderule's site...

Dik

 

[csd72]

Just to throw a spanner in the works here. I have heard of a few buildings in the UK that were built like this and the timbers were removed, the building subsequently started cracking as the timbers were effectively tying the poor quality brickwork together.

Check the quality of the brickwork before you make the assumption that the wall is better off without the timber.

 

[kieran1]

Yeah I would agree with csd72, Ive worked on a number of renovation projects with this type of construction. Removing the timbers can cause more harm than good.

Kieran